/**
* @fileoverview A class to manage state of generating a code path.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const CodePathSegment = require("./code-path-segment"),
ForkContext = require("./fork-context");
//-----------------------------------------------------------------------------
// Contexts
//-----------------------------------------------------------------------------
/**
* Represents the context in which a `break` statement can be used.
*
* A `break` statement without a label is only valid in a few places in
* JavaScript: any type of loop or a `switch` statement. Otherwise, `break`
* without a label causes a syntax error. For these contexts, `breakable` is
* set to `true` to indicate that a `break` without a label is valid.
*
* However, a `break` statement with a label is also valid inside of a labeled
* statement. For example, this is valid:
*
* a : {
* break a;
* }
*
* The `breakable` property is set false for labeled statements to indicate
* that `break` without a label is invalid.
*/
class BreakContext {
/**
* Creates a new instance.
* @param {BreakContext} upperContext The previous `BreakContext`.
* @param {boolean} breakable Indicates if we are inside a statement where
* `break` without a label will exit the statement.
* @param {string|null} label The label for the statement.
* @param {ForkContext} forkContext The current fork context.
*/
constructor(upperContext, breakable, label, forkContext) {
/**
* The previous `BreakContext`
* @type {BreakContext}
*/
this.upper = upperContext;
/**
* Indicates if we are inside a statement where `break` without a label
* will exit the statement.
* @type {boolean}
*/
this.breakable = breakable;
/**
* The label associated with the statement.
* @type {string|null}
*/
this.label = label;
/**
* The fork context for the `break`.
* @type {ForkContext}
*/
this.brokenForkContext = ForkContext.newEmpty(forkContext);
}
}
/**
* Represents the context for `ChainExpression` nodes.
*/
class ChainContext {
/**
* Creates a new instance.
* @param {ChainContext} upperContext The previous `ChainContext`.
*/
constructor(upperContext) {
/**
* The previous `ChainContext`
* @type {ChainContext}
*/
this.upper = upperContext;
/**
* The number of choice contexts inside of the `ChainContext`.
* @type {number}
*/
this.choiceContextCount = 0;
}
}
/**
* Represents a choice in the code path.
*
* Choices are created by logical operators such as `&&`, loops, conditionals,
* and `if` statements. This is the point at which the code path has a choice of
* which direction to go.
*
* The result of a choice might be in the left (test) expression of another choice,
* and in that case, may create a new fork. For example, `a || b` is a choice
* but does not create a new fork because the result of the expression is
* not used as the test expression in another expression. In this case,
* `isForkingAsResult` is false. In the expression `a || b || c`, the `a || b`
* expression appears as the test expression for `|| c`, so the
* result of `a || b` creates a fork because execution may or may not
* continue to `|| c`. `isForkingAsResult` for `a || b` in this case is true
* while `isForkingAsResult` for `|| c` is false. (`isForkingAsResult` is always
* false for `if` statements, conditional expressions, and loops.)
*
* All of the choices except one (`??`) operate on a true/false fork, meaning if
* true go one way and if false go the other (tracked by `trueForkContext` and
* `falseForkContext`). The `??` operator doesn't operate on true/false because
* the left expression is evaluated to be nullish or not, so only if nullish do
* we fork to the right expression (tracked by `nullishForkContext`).
*/
class ChoiceContext {
/**
* Creates a new instance.
* @param {ChoiceContext} upperContext The previous `ChoiceContext`.
* @param {string} kind The kind of choice. If it's a logical or assignment expression, this
* is `"&&"` or `"||"` or `"??"`; if it's an `if` statement or
* conditional expression, this is `"test"`; otherwise, this is `"loop"`.
* @param {boolean} isForkingAsResult Indicates if the result of the choice
* creates a fork.
* @param {ForkContext} forkContext The containing `ForkContext`.
*/
constructor(upperContext, kind, isForkingAsResult, forkContext) {
/**
* The previous `ChoiceContext`
* @type {ChoiceContext}
*/
this.upper = upperContext;
/**
* The kind of choice. If it's a logical or assignment expression, this
* is `"&&"` or `"||"` or `"??"`; if it's an `if` statement or
* conditional expression, this is `"test"`; otherwise, this is `"loop"`.
* @type {string}
*/
this.kind = kind;
/**
* Indicates if the result of the choice forks the code path.
* @type {boolean}
*/
this.isForkingAsResult = isForkingAsResult;
/**
* The fork context for the `true` path of the choice.
* @type {ForkContext}
*/
this.trueForkContext = ForkContext.newEmpty(forkContext);
/**
* The fork context for the `false` path of the choice.
* @type {ForkContext}
*/
this.falseForkContext = ForkContext.newEmpty(forkContext);
/**
* The fork context for when the choice result is `null` or `undefined`.
* @type {ForkContext}
*/
this.nullishForkContext = ForkContext.newEmpty(forkContext);
/**
* Indicates if any of `trueForkContext`, `falseForkContext`, or
* `nullishForkContext` have been updated with segments from a child context.
* @type {boolean}
*/
this.processed = false;
}
}
/**
* Base class for all loop contexts.
*/
class LoopContextBase {
/**
* Creates a new instance.
* @param {LoopContext|null} upperContext The previous `LoopContext`.
* @param {string} type The AST node's `type` for the loop.
* @param {string|null} label The label for the loop from an enclosing `LabeledStatement`.
* @param {BreakContext} breakContext The context for breaking the loop.
*/
constructor(upperContext, type, label, breakContext) {
/**
* The previous `LoopContext`.
* @type {LoopContext}
*/
this.upper = upperContext;
/**
* The AST node's `type` for the loop.
* @type {string}
*/
this.type = type;
/**
* The label for the loop from an enclosing `LabeledStatement`.
* @type {string|null}
*/
this.label = label;
/**
* The fork context for when `break` is encountered.
* @type {ForkContext}
*/
this.brokenForkContext = breakContext.brokenForkContext;
}
}
/**
* Represents the context for a `while` loop.
*/
class WhileLoopContext extends LoopContextBase {
/**
* Creates a new instance.
* @param {LoopContext|null} upperContext The previous `LoopContext`.
* @param {string|null} label The label for the loop from an enclosing `LabeledStatement`.
* @param {BreakContext} breakContext The context for breaking the loop.
*/
constructor(upperContext, label, breakContext) {
super(upperContext, "WhileStatement", label, breakContext);
/**
* The hardcoded literal boolean test condition for
* the loop. Used to catch infinite or skipped loops.
* @type {boolean|undefined}
*/
this.test = void 0;
/**
* The segments representing the test condition where `continue` will
* jump to. The test condition will typically have just one segment but
* it's possible for there to be more than one.
* @type {Array<CodePathSegment>|null}
*/
this.continueDestSegments = null;
}
}
/**
* Represents the context for a `do-while` loop.
*/
class DoWhileLoopContext extends LoopContextBase {
/**
* Creates a new instance.
* @param {LoopContext|null} upperContext The previous `LoopContext`.
* @param {string|null} label The label for the loop from an enclosing `LabeledStatement`.
* @param {BreakContext} breakContext The context for breaking the loop.
* @param {ForkContext} forkContext The enclosing fork context.
*/
constructor(upperContext, label, breakContext, forkContext) {
super(upperContext, "DoWhileStatement", label, breakContext);
/**
* The hardcoded literal boolean test condition for
* the loop. Used to catch infinite or skipped loops.
* @type {boolean|undefined}
*/
this.test = void 0;
/**
* The segments at the start of the loop body. This is the only loop
* where the test comes at the end, so the first iteration always
* happens and we need a reference to the first statements.
* @type {Array<CodePathSegment>|null}
*/
this.entrySegments = null;
/**
* The fork context to follow when a `continue` is found.
* @type {ForkContext}
*/
this.continueForkContext = ForkContext.newEmpty(forkContext);
}
}
/**
* Represents the context for a `for` loop.
*/
class ForLoopContext extends LoopContextBase {
/**
* Creates a new instance.
* @param {LoopContext|null} upperContext The previous `LoopContext`.
* @param {string|null} label The label for the loop from an enclosing `LabeledStatement`.
* @param {BreakContext} breakContext The context for breaking the loop.
*/
constructor(upperContext, label, breakContext) {
super(upperContext, "ForStatement", label, breakContext);
/**
* The hardcoded literal boolean test condition for
* the loop. Used to catch infinite or skipped loops.
* @type {boolean|undefined}
*/
this.test = void 0;
/**
* The end of the init expression. This may change during the lifetime
* of the instance as we traverse the loop because some loops don't have
* an init expression.
* @type {Array<CodePathSegment>|null}
*/
this.endOfInitSegments = null;
/**
* The start of the test expression. This may change during the lifetime
* of the instance as we traverse the loop because some loops don't have
* a test expression.
* @type {Array<CodePathSegment>|null}
*/
this.testSegments = null;
/**
* The end of the test expression. This may change during the lifetime
* of the instance as we traverse the loop because some loops don't have
* a test expression.
* @type {Array<CodePathSegment>|null}
*/
this.endOfTestSegments = null;
/**
* The start of the update expression. This may change during the lifetime
* of the instance as we traverse the loop because some loops don't have
* an update expression.
* @type {Array<CodePathSegment>|null}
*/
this.updateSegments = null;
/**
* The end of the update expresion. This may change during the lifetime
* of the instance as we traverse the loop because some loops don't have
* an update expression.
* @type {Array<CodePathSegment>|null}
*/
this.endOfUpdateSegments = null;
/**
* The segments representing the test condition where `continue` will
* jump to. The test condition will typically have just one segment but
* it's possible for there to be more than one. This may change during the
* lifetime of the instance as we traverse the loop because some loops
* don't have an update expression. When there is an update expression, this
* will end up pointing to that expression; otherwise it will end up pointing
* to the test expression.
* @type {Array<CodePathSegment>|null}
*/
this.continueDestSegments = null;
}
}
/**
* Represents the context for a `for-in` loop.
*
* Terminology:
* - "left" means the part of the loop to the left of the `in` keyword. For
* example, in `for (var x in y)`, the left is `var x`.
* - "right" means the part of the loop to the right of the `in` keyword. For
* example, in `for (var x in y)`, the right is `y`.
*/
class ForInLoopContext extends LoopContextBase {
/**
* Creates a new instance.
* @param {LoopContext|null} upperContext The previous `LoopContext`.
* @param {string|null} label The label for the loop from an enclosing `LabeledStatement`.
* @param {BreakContext} breakContext The context for breaking the loop.
*/
constructor(upperContext, label, breakContext) {
super(upperContext, "ForInStatement", label, breakContext);
/**
* The segments that came immediately before the start of the loop.
* This allows you to traverse backwards out of the loop into the
* surrounding code. This is necessary to evaluate the right expression
* correctly, as it must be evaluated in the same way as the left
* expression, but the pointer to these segments would otherwise be
* lost if not stored on the instance. Once the right expression has
* been evaluated, this property is no longer used.
* @type {Array<CodePathSegment>|null}
*/
this.prevSegments = null;
/**
* Segments representing the start of everything to the left of the
* `in` keyword. This can be used to move forward towards
* `endOfLeftSegments`. `leftSegments` and `endOfLeftSegments` are
* effectively the head and tail of a doubly-linked list.
* @type {Array<CodePathSegment>|null}
*/
this.leftSegments = null;
/**
* Segments representing the end of everything to the left of the
* `in` keyword. This can be used to move backward towards `leftSegments`.
* `leftSegments` and `endOfLeftSegments` are effectively the head
* and tail of a doubly-linked list.
* @type {Array<CodePathSegment>|null}
*/
this.endOfLeftSegments = null;
/**
* The segments representing the left expression where `continue` will
* jump to. In `for-in` loops, `continue` must always re-execute the
* left expression each time through the loop. This contains the same
* segments as `leftSegments`, but is duplicated here so each loop
* context has the same property pointing to where `continue` should
* end up.
* @type {Array<CodePathSegment>|null}
*/
this.continueDestSegments = null;
}
}
/**
* Represents the context for a `for-of` loop.
*/
class ForOfLoopContext extends LoopContextBase {
/**
* Creates a new instance.
* @param {LoopContext|null} upperContext The previous `LoopContext`.
* @param {string|null} label The label for the loop from an enclosing `LabeledStatement`.
* @param {BreakContext} breakContext The context for breaking the loop.
*/
constructor(upperContext, label, breakContext) {
super(upperContext, "ForOfStatement", label, breakContext);
/**
* The segments that came immediately before the start of the loop.
* This allows you to traverse backwards out of the loop into the
* surrounding code. This is necessary to evaluate the right expression
* correctly, as it must be evaluated in the same way as the left
* expression, but the pointer to these segments would otherwise be
* lost if not stored on the instance. Once the right expression has
* been evaluated, this property is no longer used.
* @type {Array<CodePathSegment>|null}
*/
this.prevSegments = null;
/**
* Segments representing the start of everything to the left of the
* `of` keyword. This can be used to move forward towards
* `endOfLeftSegments`. `leftSegments` and `endOfLeftSegments` are
* effectively the head and tail of a doubly-linked list.
* @type {Array<CodePathSegment>|null}
*/
this.leftSegments = null;
/**
* Segments representing the end of everything to the left of the
* `of` keyword. This can be used to move backward towards `leftSegments`.
* `leftSegments` and `endOfLeftSegments` are effectively the head
* and tail of a doubly-linked list.
* @type {Array<CodePathSegment>|null}
*/
this.endOfLeftSegments = null;
/**
* The segments representing the left expression where `continue` will
* jump to. In `for-in` loops, `continue` must always re-execute the
* left expression each time through the loop. This contains the same
* segments as `leftSegments`, but is duplicated here so each loop
* context has the same property pointing to where `continue` should
* end up.
* @type {Array<CodePathSegment>|null}
*/
this.continueDestSegments = null;
}
}
/**
* Represents the context for any loop.
* @typedef {WhileLoopContext|DoWhileLoopContext|ForLoopContext|ForInLoopContext|ForOfLoopContext} LoopContext
*/
/**
* Represents the context for a `switch` statement.
*/
class SwitchContext {
/**
* Creates a new instance.
* @param {SwitchContext} upperContext The previous context.
* @param {boolean} hasCase Indicates if there is at least one `case` statement.
* `default` doesn't count.
*/
constructor(upperContext, hasCase) {
/**
* The previous context.
* @type {SwitchContext}
*/
this.upper = upperContext;
/**
* Indicates if there is at least one `case` statement. `default` doesn't count.
* @type {boolean}
*/
this.hasCase = hasCase;
/**
* The `default` keyword.
* @type {Array<CodePathSegment>|null}
*/
this.defaultSegments = null;
/**
* The default case body starting segments.
* @type {Array<CodePathSegment>|null}
*/
this.defaultBodySegments = null;
/**
* Indicates if a `default` case and is empty exists.
* @type {boolean}
*/
this.foundEmptyDefault = false;
/**
* Indicates that a `default` exists and is the last case.
* @type {boolean}
*/
this.lastIsDefault = false;
/**
* The number of fork contexts created. This is equivalent to the
* number of `case` statements plus a `default` statement (if present).
* @type {number}
*/
this.forkCount = 0;
}
}
/**
* Represents the context for a `try` statement.
*/
class TryContext {
/**
* Creates a new instance.
* @param {TryContext} upperContext The previous context.
* @param {boolean} hasFinalizer Indicates if the `try` statement has a
* `finally` block.
* @param {ForkContext} forkContext The enclosing fork context.
*/
constructor(upperContext, hasFinalizer, forkContext) {
/**
* The previous context.
* @type {TryContext}
*/
this.upper = upperContext;
/**
* Indicates if the `try` statement has a `finally` block.
* @type {boolean}
*/
this.hasFinalizer = hasFinalizer;
/**
* Tracks the traversal position inside of the `try` statement. This is
* used to help determine the context necessary to create paths because
* a `try` statement may or may not have `catch` or `finally` blocks,
* and code paths behave differently in those blocks.
* @type {"try"|"catch"|"finally"}
*/
this.position = "try";
/**
* If the `try` statement has a `finally` block, this affects how a
* `return` statement behaves in the `try` block. Without `finally`,
* `return` behaves as usual and doesn't require a fork; with `finally`,
* `return` forks into the `finally` block, so we need a fork context
* to track it.
* @type {ForkContext|null}
*/
this.returnedForkContext = hasFinalizer
? ForkContext.newEmpty(forkContext)
: null;
/**
* When a `throw` occurs inside of a `try` block, the code path forks
* into the `catch` or `finally` blocks, and this fork context tracks
* that path.
* @type {ForkContext}
*/
this.thrownForkContext = ForkContext.newEmpty(forkContext);
/**
* Indicates if the last segment in the `try` block is reachable.
* @type {boolean}
*/
this.lastOfTryIsReachable = false;
/**
* Indicates if the last segment in the `catch` block is reachable.
* @type {boolean}
*/
this.lastOfCatchIsReachable = false;
}
}
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Adds given segments into the `dest` array.
* If the `others` array does not include the given segments, adds to the `all`
* array as well.
*
* This adds only reachable and used segments.
* @param {CodePathSegment[]} dest A destination array (`returnedSegments` or `thrownSegments`).
* @param {CodePathSegment[]} others Another destination array (`returnedSegments` or `thrownSegments`).
* @param {CodePathSegment[]} all The unified destination array (`finalSegments`).
* @param {CodePathSegment[]} segments Segments to add.
* @returns {void}
*/
function addToReturnedOrThrown(dest, others, all, segments) {
for (let i = 0; i < segments.length; ++i) {
const segment = segments[i];
dest.push(segment);
if (!others.includes(segment)) {
all.push(segment);
}
}
}
/**
* Gets a loop context for a `continue` statement based on a given label.
* @param {CodePathState} state The state to search within.
* @param {string|null} label The label of a `continue` statement.
* @returns {LoopContext} A loop-context for a `continue` statement.
*/
function getContinueContext(state, label) {
if (!label) {
return state.loopContext;
}
let context = state.loopContext;
while (context) {
if (context.label === label) {
return context;
}
context = context.upper;
}
/* c8 ignore next */
return null;
}
/**
* Gets a context for a `break` statement.
* @param {CodePathState} state The state to search within.
* @param {string|null} label The label of a `break` statement.
* @returns {BreakContext} A context for a `break` statement.
*/
function getBreakContext(state, label) {
let context = state.breakContext;
while (context) {
if (label ? context.label === label : context.breakable) {
return context;
}
context = context.upper;
}
/* c8 ignore next */
return null;
}
/**
* Gets a context for a `return` statement. There is just one special case:
* if there is a `try` statement with a `finally` block, because that alters
* how `return` behaves; otherwise, this just passes through the given state.
* @param {CodePathState} state The state to search within
* @returns {TryContext|CodePathState} A context for a `return` statement.
*/
function getReturnContext(state) {
let context = state.tryContext;
while (context) {
if (context.hasFinalizer && context.position !== "finally") {
return context;
}
context = context.upper;
}
return state;
}
/**
* Gets a context for a `throw` statement. There is just one special case:
* if there is a `try` statement with a `finally` block and we are inside of
* a `catch` because that changes how `throw` behaves; otherwise, this just
* passes through the given state.
* @param {CodePathState} state The state to search within.
* @returns {TryContext|CodePathState} A context for a `throw` statement.
*/
function getThrowContext(state) {
let context = state.tryContext;
while (context) {
if (context.position === "try" ||
(context.hasFinalizer && context.position === "catch")
) {
return context;
}
context = context.upper;
}
return state;
}
/**
* Removes a given value from a given array.
* @param {any[]} elements An array to remove the specific element.
* @param {any} value The value to be removed.
* @returns {void}
*/
function removeFromArray(elements, value) {
elements.splice(elements.indexOf(value), 1);
}
/**
* Disconnect given segments.
*
* This is used in a process for switch statements.
* If there is the "default" chunk before other cases, the order is different
* between node's and running's.
* @param {CodePathSegment[]} prevSegments Forward segments to disconnect.
* @param {CodePathSegment[]} nextSegments Backward segments to disconnect.
* @returns {void}
*/
function disconnectSegments(prevSegments, nextSegments) {
for (let i = 0; i < prevSegments.length; ++i) {
const prevSegment = prevSegments[i];
const nextSegment = nextSegments[i];
removeFromArray(prevSegment.nextSegments, nextSegment);
removeFromArray(prevSegment.allNextSegments, nextSegment);
removeFromArray(nextSegment.prevSegments, prevSegment);
removeFromArray(nextSegment.allPrevSegments, prevSegment);
}
}
/**
* Creates looping path between two arrays of segments, ensuring that there are
* paths going between matching segments in the arrays.
* @param {CodePathState} state The state to operate on.
* @param {CodePathSegment[]} unflattenedFromSegments Segments which are source.
* @param {CodePathSegment[]} unflattenedToSegments Segments which are destination.
* @returns {void}
*/
function makeLooped(state, unflattenedFromSegments, unflattenedToSegments) {
const fromSegments = CodePathSegment.flattenUnusedSegments(unflattenedFromSegments);
const toSegments = CodePathSegment.flattenUnusedSegments(unflattenedToSegments);
const end = Math.min(fromSegments.length, toSegments.length);
/*
* This loop effectively updates a doubly-linked list between two collections
* of segments making sure that segments in the same array indices are
* combined to create a path.
*/
for (let i = 0; i < end; ++i) {
// get the segments in matching array indices
const fromSegment = fromSegments[i];
const toSegment = toSegments[i];
/*
* If the destination segment is reachable, then create a path from the
* source segment to the destination segment.
*/
if (toSegment.reachable) {
fromSegment.nextSegments.push(toSegment);
}
/*
* If the source segment is reachable, then create a path from the
* destination segment back to the source segment.
*/
if (fromSegment.reachable) {
toSegment.prevSegments.push(fromSegment);
}
/*
* Also update the arrays that don't care if the segments are reachable
* or not. This should always happen regardless of anything else.
*/
fromSegment.allNextSegments.push(toSegment);
toSegment.allPrevSegments.push(fromSegment);
/*
* If the destination segment has at least two previous segments in its
* path then that means there was one previous segment before this iteration
* of the loop was executed. So, we need to mark the source segment as
* looped.
*/
if (toSegment.allPrevSegments.length >= 2) {
CodePathSegment.markPrevSegmentAsLooped(toSegment, fromSegment);
}
// let the code path analyzer know that there's been a loop created
state.notifyLooped(fromSegment, toSegment);
}
}
/**
* Finalizes segments of `test` chunk of a ForStatement.
*
* - Adds `false` paths to paths which are leaving from the loop.
* - Sets `true` paths to paths which go to the body.
* @param {LoopContext} context A loop context to modify.
* @param {ChoiceContext} choiceContext A choice context of this loop.
* @param {CodePathSegment[]} head The current head paths.
* @returns {void}
*/
function finalizeTestSegmentsOfFor(context, choiceContext, head) {
/*
* If this choice context doesn't already contain paths from a
* child context, then add the current head to each potential path.
*/
if (!choiceContext.processed) {
choiceContext.trueForkContext.add(head);
choiceContext.falseForkContext.add(head);
choiceContext.nullishForkContext.add(head);
}
/*
* If the test condition isn't a hardcoded truthy value, then `break`
* must follow the same path as if the test condition is false. To represent
* that, we append the path for when the loop test is false (represented by
* `falseForkContext`) to the `brokenForkContext`.
*/
if (context.test !== true) {
context.brokenForkContext.addAll(choiceContext.falseForkContext);
}
context.endOfTestSegments = choiceContext.trueForkContext.makeNext(0, -1);
}
//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
/**
* A class which manages state to analyze code paths.
*/
class CodePathState {
/**
* Creates a new instance.
* @param {IdGenerator} idGenerator An id generator to generate id for code
* path segments.
* @param {Function} onLooped A callback function to notify looping.
*/
constructor(idGenerator, onLooped) {
/**
* The ID generator to use when creating new segments.
* @type {IdGenerator}
*/
this.idGenerator = idGenerator;
/**
* A callback function to call when there is a loop.
* @type {Function}
*/
this.notifyLooped = onLooped;
/**
* The root fork context for this state.
* @type {ForkContext}
*/
this.forkContext = ForkContext.newRoot(idGenerator);
/**
* Context for logical expressions, conditional expressions, `if` statements,
* and loops.
* @type {ChoiceContext}
*/
this.choiceContext = null;
/**
* Context for `switch` statements.
* @type {SwitchContext}
*/
this.switchContext = null;
/**
* Context for `try` statements.
* @type {TryContext}
*/
this.tryContext = null;
/**
* Context for loop statements.
* @type {LoopContext}
*/
this.loopContext = null;
/**
* Context for `break` statements.
* @type {BreakContext}
*/
this.breakContext = null;
/**
* Context for `ChainExpression` nodes.
* @type {ChainContext}
*/
this.chainContext = null;
/**
* An array that tracks the current segments in the state. The array
* starts empty and segments are added with each `onCodePathSegmentStart`
* event and removed with each `onCodePathSegmentEnd` event. Effectively,
* this is tracking the code path segment traversal as the state is
* modified.
* @type {Array<CodePathSegment>}
*/
this.currentSegments = [];
/**
* Tracks the starting segment for this path. This value never changes.
* @type {CodePathSegment}
*/
this.initialSegment = this.forkContext.head[0];
/**
* The final segments of the code path which are either `return` or `throw`.
* This is a union of the segments in `returnedForkContext` and `thrownForkContext`.
* @type {Array<CodePathSegment>}
*/
this.finalSegments = [];
/**
* The final segments of the code path which are `return`. These
* segments are also contained in `finalSegments`.
* @type {Array<CodePathSegment>}
*/
this.returnedForkContext = [];
/**
* The final segments of the code path which are `throw`. These
* segments are also contained in `finalSegments`.
* @type {Array<CodePathSegment>}
*/
this.thrownForkContext = [];
/*
* We add an `add` method so that these look more like fork contexts and
* can be used interchangeably when a fork context is needed to add more
* segments to a path.
*
* Ultimately, we want anything added to `returned` or `thrown` to also
* be added to `final`. We only add reachable and used segments to these
* arrays.
*/
const final = this.finalSegments;
const returned = this.returnedForkContext;
const thrown = this.thrownForkContext;
returned.add = addToReturnedOrThrown.bind(null, returned, thrown, final);
thrown.add = addToReturnedOrThrown.bind(null, thrown, returned, final);
}
/**
* A passthrough property exposing the current pointer as part of the API.
* @type {CodePathSegment[]}
*/
get headSegments() {
return this.forkContext.head;
}
/**
* The parent forking context.
* This is used for the root of new forks.
* @type {ForkContext}
*/
get parentForkContext() {
const current = this.forkContext;
return current && current.upper;
}
/**
* Creates and stacks new forking context.
* @param {boolean} forkLeavingPath A flag which shows being in a
* "finally" block.
* @returns {ForkContext} The created context.
*/
pushForkContext(forkLeavingPath) {
this.forkContext = ForkContext.newEmpty(
this.forkContext,
forkLeavingPath
);
return this.forkContext;
}
/**
* Pops and merges the last forking context.
* @returns {ForkContext} The last context.
*/
popForkContext() {
const lastContext = this.forkContext;
this.forkContext = lastContext.upper;
this.forkContext.replaceHead(lastContext.makeNext(0, -1));
return lastContext;
}
/**
* Creates a new path.
* @returns {void}
*/
forkPath() {
this.forkContext.add(this.parentForkContext.makeNext(-1, -1));
}
/**
* Creates a bypass path.
* This is used for such as IfStatement which does not have "else" chunk.
* @returns {void}
*/
forkBypassPath() {
this.forkContext.add(this.parentForkContext.head);
}
//--------------------------------------------------------------------------
// ConditionalExpression, LogicalExpression, IfStatement
//--------------------------------------------------------------------------
/**
* Creates a context for ConditionalExpression, LogicalExpression, AssignmentExpression (logical assignments only),
* IfStatement, WhileStatement, DoWhileStatement, or ForStatement.
*
* LogicalExpressions have cases that it goes different paths between the
* `true` case and the `false` case.
*
* For Example:
*
* if (a || b) {
* foo();
* } else {
* bar();
* }
*
* In this case, `b` is evaluated always in the code path of the `else`
* block, but it's not so in the code path of the `if` block.
* So there are 3 paths.
*
* a -> foo();
* a -> b -> foo();
* a -> b -> bar();
* @param {string} kind A kind string.
* If the new context is LogicalExpression's or AssignmentExpression's, this is `"&&"` or `"||"` or `"??"`.
* If it's IfStatement's or ConditionalExpression's, this is `"test"`.
* Otherwise, this is `"loop"`.
* @param {boolean} isForkingAsResult Indicates if the result of the choice
* creates a fork.
* @returns {void}
*/
pushChoiceContext(kind, isForkingAsResult) {
this.choiceContext = new ChoiceContext(this.choiceContext, kind, isForkingAsResult, this.forkContext);
}
/**
* Pops the last choice context and finalizes it.
* This is called upon leaving a node that represents a choice.
* @throws {Error} (Unreachable.)
* @returns {ChoiceContext} The popped context.
*/
popChoiceContext() {
const poppedChoiceContext = this.choiceContext;
const forkContext = this.forkContext;
const head = forkContext.head;
this.choiceContext = poppedChoiceContext.upper;
switch (poppedChoiceContext.kind) {
case "&&":
case "||":
case "??":
/*
* The `head` are the path of the right-hand operand.
* If we haven't previously added segments from child contexts,
* then we add these segments to all possible forks.
*/
if (!poppedChoiceContext.processed) {
poppedChoiceContext.trueForkContext.add(head);
poppedChoiceContext.falseForkContext.add(head);
poppedChoiceContext.nullishForkContext.add(head);
}
/*
* If this context is the left (test) expression for another choice
* context, such as `a || b` in the expression `a || b || c`,
* then we take the segments for this context and move them up
* to the parent context.
*/
if (poppedChoiceContext.isForkingAsResult) {
const parentContext = this.choiceContext;
parentContext.trueForkContext.addAll(poppedChoiceContext.trueForkContext);
parentContext.falseForkContext.addAll(poppedChoiceContext.falseForkContext);
parentContext.nullishForkContext.addAll(poppedChoiceContext.nullishForkContext);
parentContext.processed = true;
// Exit early so we don't collapse all paths into one.
return poppedChoiceContext;
}
break;
case "test":
if (!poppedChoiceContext.processed) {
/*
* The head segments are the path of the `if` block here.
* Updates the `true` path with the end of the `if` block.
*/
poppedChoiceContext.trueForkContext.clear();
poppedChoiceContext.trueForkContext.add(head);
} else {
/*
* The head segments are the path of the `else` block here.
* Updates the `false` path with the end of the `else`
* block.
*/
poppedChoiceContext.falseForkContext.clear();
poppedChoiceContext.falseForkContext.add(head);
}
break;
case "loop":
/*
* Loops are addressed in `popLoopContext()` so just return
* the context without modification.
*/
return poppedChoiceContext;
/* c8 ignore next */
default:
throw new Error("unreachable");
}
/*
* Merge the true path with the false path to create a single path.
*/
const combinedForkContext = poppedChoiceContext.trueForkContext;
combinedForkContext.addAll(poppedChoiceContext.falseForkContext);
forkContext.replaceHead(combinedForkContext.makeNext(0, -1));
return poppedChoiceContext;
}
/**
* Creates a code path segment to represent right-hand operand of a logical
* expression.
* This is called in the preprocessing phase when entering a node.
* @throws {Error} (Unreachable.)
* @returns {void}
*/
makeLogicalRight() {
const currentChoiceContext = this.choiceContext;
const forkContext = this.forkContext;
if (currentChoiceContext.processed) {
/*
* This context was already assigned segments from a child
* choice context. In this case, we are concerned only about
* the path that does not short-circuit and so ends up on the
* right-hand operand of the logical expression.
*/
let prevForkContext;
switch (currentChoiceContext.kind) {
case "&&": // if true then go to the right-hand side.
prevForkContext = currentChoiceContext.trueForkContext;
break;
case "||": // if false then go to the right-hand side.
prevForkContext = currentChoiceContext.falseForkContext;
break;
case "??": // Both true/false can short-circuit, so needs the third path to go to the right-hand side. That's nullishForkContext.
prevForkContext = currentChoiceContext.nullishForkContext;
break;
default:
throw new Error("unreachable");
}
/*
* Create the segment for the right-hand operand of the logical expression
* and adjust the fork context pointer to point there. The right-hand segment
* is added at the end of all segments in `prevForkContext`.
*/
forkContext.replaceHead(prevForkContext.makeNext(0, -1));
/*
* We no longer need this list of segments.
*
* Reset `processed` because we've removed the segments from the child
* choice context. This allows `popChoiceContext()` to continue adding
* segments later.
*/
prevForkContext.clear();
currentChoiceContext.processed = false;
} else {
/*
* This choice context was not assigned segments from a child
* choice context, which means that it's a terminal logical
* expression.
*
* `head` is the segments for the left-hand operand of the
* logical expression.
*
* Each of the fork contexts below are empty at this point. We choose
* the path(s) that will short-circuit and add the segment for the
* left-hand operand to it. Ultimately, this will be the only segment
* in that path due to the short-circuting, so we are just seeding
* these paths to start.
*/
switch (currentChoiceContext.kind) {
case "&&":
/*
* In most contexts, when a && expression evaluates to false,
* it short circuits, so we need to account for that by setting
* the `falseForkContext` to the left operand.
*
* When a && expression is the left-hand operand for a ??
* expression, such as `(a && b) ?? c`, a nullish value will
* also short-circuit in a different way than a false value,
* so we also set the `nullishForkContext` to the left operand.
* This path is only used with a ?? expression and is thrown
* away for any other type of logical expression, so it's safe
* to always add.
*/
currentChoiceContext.falseForkContext.add(forkContext.head);
currentChoiceContext.nullishForkContext.add(forkContext.head);
break;
case "||": // the true path can short-circuit.
currentChoiceContext.trueForkContext.add(forkContext.head);
break;
case "??": // both can short-circuit.
currentChoiceContext.trueForkContext.add(forkContext.head);
currentChoiceContext.falseForkContext.add(forkContext.head);
break;
default:
throw new Error("unreachable");
}
/*
* Create the segment for the right-hand operand of the logical expression
* and adjust the fork context pointer to point there.
*/
forkContext.replaceHead(forkContext.makeNext(-1, -1));
}
}
/**
* Makes a code path segment of the `if` block.
* @returns {void}
*/
makeIfConsequent() {
const context = this.choiceContext;
const forkContext = this.forkContext;
/*
* If any result were not transferred from child contexts,
* this sets the head segments to both cases.
* The head segments are the path of the test expression.
*/
if (!context.processed) {
context.trueForkContext.add(forkContext.head);
context.falseForkContext.add(forkContext.head);
context.nullishForkContext.add(forkContext.head);
}
context.processed = false;
// Creates new path from the `true` case.
forkContext.replaceHead(
context.trueForkContext.makeNext(0, -1)
);
}
/**
* Makes a code path segment of the `else` block.
* @returns {void}
*/
makeIfAlternate() {
const context = this.choiceContext;
const forkContext = this.forkContext;
/*
* The head segments are the path of the `if` block.
* Updates the `true` path with the end of the `if` block.
*/
context.trueForkContext.clear();
context.trueForkContext.add(forkContext.head);
context.processed = true;
// Creates new path from the `false` case.
forkContext.replaceHead(
context.falseForkContext.makeNext(0, -1)
);
}
//--------------------------------------------------------------------------
// ChainExpression
//--------------------------------------------------------------------------
/**
* Pushes a new `ChainExpression` context to the stack. This method is
* called when entering a `ChainExpression` node. A chain context is used to
* count forking in the optional chain then merge them on the exiting from the
* `ChainExpression` node.
* @returns {void}
*/
pushChainContext() {
this.chainContext = new ChainContext(this.chainContext);
}
/**
* Pop a `ChainExpression` context from the stack. This method is called on
* exiting from each `ChainExpression` node. This merges all forks of the
* last optional chaining.
* @returns {void}
*/
popChainContext() {
const context = this.chainContext;
this.chainContext = context.upper;
// pop all choice contexts of this.
for (let i = context.choiceContextCount; i > 0; --i) {
this.popChoiceContext();
}
}
/**
* Create a choice context for optional access.
* This method is called on entering to each `(Call|Member)Expression[optional=true]` node.
* This creates a choice context as similar to `LogicalExpression[operator="??"]` node.
* @returns {void}
*/
makeOptionalNode() {
if (this.chainContext) {
this.chainContext.choiceContextCount += 1;
this.pushChoiceContext("??", false);
}
}
/**
* Create a fork.
* This method is called on entering to the `arguments|property` property of each `(Call|Member)Expression` node.
* @returns {void}
*/
makeOptionalRight() {
if (this.chainContext) {
this.makeLogicalRight();
}
}
//--------------------------------------------------------------------------
// SwitchStatement
//--------------------------------------------------------------------------
/**
* Creates a context object of SwitchStatement and stacks it.
* @param {boolean} hasCase `true` if the switch statement has one or more
* case parts.
* @param {string|null} label The label text.
* @returns {void}
*/
pushSwitchContext(hasCase, label) {
this.switchContext = new SwitchContext(this.switchContext, hasCase);
this.pushBreakContext(true, label);
}
/**
* Pops the last context of SwitchStatement and finalizes it.
*
* - Disposes all forking stack for `case` and `default`.
* - Creates the next code path segment from `context.brokenForkContext`.
* - If the last `SwitchCase` node is not a `default` part, creates a path
* to the `default` body.
* @returns {void}
*/
popSwitchContext() {
const context = this.switchContext;
this.switchContext = context.upper;
const forkContext = this.forkContext;
const brokenForkContext = this.popBreakContext().brokenForkContext;
if (context.forkCount === 0) {
/*
* When there is only one `default` chunk and there is one or more
* `break` statements, even if forks are nothing, it needs to merge
* those.
*/
if (!brokenForkContext.empty) {
brokenForkContext.add(forkContext.makeNext(-1, -1));
forkContext.replaceHead(brokenForkContext.makeNext(0, -1));
}
return;
}
const lastSegments = forkContext.head;
this.forkBypassPath();
const lastCaseSegments = forkContext.head;
/*
* `brokenForkContext` is used to make the next segment.
* It must add the last segment into `brokenForkContext`.
*/
brokenForkContext.add(lastSegments);
/*
* Any value that doesn't match a `case` test should flow to the default
* case. That happens normally when the default case is last in the `switch`,
* but if it's not, we need to rewire some of the paths to be correct.
*/
if (!context.lastIsDefault) {
if (context.defaultBodySegments) {
/*
* There is a non-empty default case, so remove the path from the `default`
* label to its body for an accurate representation.
*/
disconnectSegments(context.defaultSegments, context.defaultBodySegments);
/*
* Connect the path from the last non-default case to the body of the
* default case.
*/
makeLooped(this, lastCaseSegments, context.defaultBodySegments);
} else {
/*
* There is no default case, so we treat this as if the last case
* had a `break` in it.
*/
brokenForkContext.add(lastCaseSegments);
}
}
// Traverse up to the original fork context for the `switch` statement
for (let i = 0; i < context.forkCount; ++i) {
this.forkContext = this.forkContext.upper;
}
/*
* Creates a path from all `brokenForkContext` paths.
* This is a path after `switch` statement.
*/
this.forkContext.replaceHead(brokenForkContext.makeNext(0, -1));
}
/**
* Makes a code path segment for a `SwitchCase` node.
* @param {boolean} isCaseBodyEmpty `true` if the body is empty.
* @param {boolean} isDefaultCase `true` if the body is the default case.
* @returns {void}
*/
makeSwitchCaseBody(isCaseBodyEmpty, isDefaultCase) {
const context = this.switchContext;
if (!context.hasCase) {
return;
}
/*
* Merge forks.
* The parent fork context has two segments.
* Those are from the current `case` and the body of the previous case.
*/
const parentForkContext = this.forkContext;
const forkContext = this.pushForkContext();
forkContext.add(parentForkContext.makeNext(0, -1));
/*
* Add information about the default case.
*
* The purpose of this is to identify the starting segments for the
* default case to make sure there is a path there.
*/
if (isDefaultCase) {
/*
* This is the default case in the `switch`.
*
* We first save the current pointer as `defaultSegments` to point
* to the `default` keyword.
*/
context.defaultSegments = parentForkContext.head;
/*
* If the body of the case is empty then we just set
* `foundEmptyDefault` to true; otherwise, we save a reference
* to the current pointer as `defaultBodySegments`.
*/
if (isCaseBodyEmpty) {
context.foundEmptyDefault = true;
} else {
context.defaultBodySegments = forkContext.head;
}
} else {
/*
* This is not the default case in the `switch`.
*
* If it's not empty and there is already an empty default case found,
* that means the default case actually comes before this case,
* and that it will fall through to this case. So, we can now
* ignore the previous default case (reset `foundEmptyDefault` to false)
* and set `defaultBodySegments` to the current segments because this is
* effectively the new default case.
*/
if (!isCaseBodyEmpty && context.foundEmptyDefault) {
context.foundEmptyDefault = false;
context.defaultBodySegments = forkContext.head;
}
}
// keep track if the default case ends up last
context.lastIsDefault = isDefaultCase;
context.forkCount += 1;
}
//--------------------------------------------------------------------------
// TryStatement
//--------------------------------------------------------------------------
/**
* Creates a context object of TryStatement and stacks it.
* @param {boolean} hasFinalizer `true` if the try statement has a
* `finally` block.
* @returns {void}
*/
pushTryContext(hasFinalizer) {
this.tryContext = new TryContext(this.tryContext, hasFinalizer, this.forkContext);
}
/**
* Pops the last context of TryStatement and finalizes it.
* @returns {void}
*/
popTryContext() {
const context = this.tryContext;
this.tryContext = context.upper;
/*
* If we're inside the `catch` block, that means there is no `finally`,
* so we can process the `try` and `catch` blocks the simple way and
* merge their two paths.
*/
if (context.position === "catch") {
this.popForkContext();
return;
}
/*
* The following process is executed only when there is a `finally`
* block.
*/
const originalReturnedForkContext = context.returnedForkContext;
const originalThrownForkContext = context.thrownForkContext;
// no `return` or `throw` in `try` or `catch` so there's nothing left to do
if (originalReturnedForkContext.empty && originalThrownForkContext.empty) {
return;
}
/*
* The following process is executed only when there is a `finally`
* block and there was a `return` or `throw` in the `try` or `catch`
* blocks.
*/
// Separate head to normal paths and leaving paths.
const headSegments = this.forkContext.head;
this.forkContext = this.forkContext.upper;
const normalSegments = headSegments.slice(0, headSegments.length / 2 | 0);
const leavingSegments = headSegments.slice(headSegments.length / 2 | 0);
// Forwards the leaving path to upper contexts.
if (!originalReturnedForkContext.empty) {
getReturnContext(this).returnedForkContext.add(leavingSegments);
}
if (!originalThrownForkContext.empty) {
getThrowContext(this).thrownForkContext.add(leavingSegments);
}
// Sets the normal path as the next.
this.forkContext.replaceHead(normalSegments);
/*
* If both paths of the `try` block and the `catch` block are
* unreachable, the next path becomes unreachable as well.
*/
if (!context.lastOfTryIsReachable && !context.lastOfCatchIsReachable) {
this.forkContext.makeUnreachable();
}
}
/**
* Makes a code path segment for a `catch` block.
* @returns {void}
*/
makeCatchBlock() {
const context = this.tryContext;
const forkContext = this.forkContext;
const originalThrownForkContext = context.thrownForkContext;
/*
* We are now in a catch block so we need to update the context
* with that information. This includes creating a new fork
* context in case we encounter any `throw` statements here.
*/
context.position = "catch";
context.thrownForkContext = ForkContext.newEmpty(forkContext);
context.lastOfTryIsReachable = forkContext.reachable;
// Merge the thrown paths from the `try` and `catch` blocks
originalThrownForkContext.add(forkContext.head);
const thrownSegments = originalThrownForkContext.makeNext(0, -1);
// Fork to a bypass and the merged thrown path.
this.pushForkContext();
this.forkBypassPath();
this.forkContext.add(thrownSegments);
}
/**
* Makes a code path segment for a `finally` block.
*
* In the `finally` block, parallel paths are created. The parallel paths
* are used as leaving-paths. The leaving-paths are paths from `return`
* statements and `throw` statements in a `try` block or a `catch` block.
* @returns {void}
*/
makeFinallyBlock() {
const context = this.tryContext;
let forkContext = this.forkContext;
const originalReturnedForkContext = context.returnedForkContext;
const originalThrownForContext = context.thrownForkContext;
const headOfLeavingSegments = forkContext.head;
// Update state.
if (context.position === "catch") {
// Merges two paths from the `try` block and `catch` block.
this.popForkContext();
forkContext = this.forkContext;
context.lastOfCatchIsReachable = forkContext.reachable;
} else {
context.lastOfTryIsReachable = forkContext.reachable;
}
context.position = "finally";
/*
* If there was no `return` or `throw` in either the `try` or `catch`
* blocks, then there's no further code paths to create for `finally`.
*/
if (originalReturnedForkContext.empty && originalThrownForContext.empty) {
// This path does not leave.
return;
}
/*
* Create a parallel segment from merging returned and thrown.
* This segment will leave at the end of this `finally` block.
*/
const segments = forkContext.makeNext(-1, -1);
for (let i = 0; i < forkContext.count; ++i) {
const prevSegsOfLeavingSegment = [headOfLeavingSegments[i]];
for (let j = 0; j < originalReturnedForkContext.segmentsList.length; ++j) {
prevSegsOfLeavingSegment.push(originalReturnedForkContext.segmentsList[j][i]);
}
for (let j = 0; j < originalThrownForContext.segmentsList.length; ++j) {
prevSegsOfLeavingSegment.push(originalThrownForContext.segmentsList[j][i]);
}
segments.push(
CodePathSegment.newNext(
this.idGenerator.next(),
prevSegsOfLeavingSegment
)
);
}
this.pushForkContext(true);
this.forkContext.add(segments);
}
/**
* Makes a code path segment from the first throwable node to the `catch`
* block or the `finally` block.
* @returns {void}
*/
makeFirstThrowablePathInTryBlock() {
const forkContext = this.forkContext;
if (!forkContext.reachable) {
return;
}
const context = getThrowContext(this);
if (context === this ||
context.position !== "try" ||
!context.thrownForkContext.empty
) {
return;
}
context.thrownForkContext.add(forkContext.head);
forkContext.replaceHead(forkContext.makeNext(-1, -1));
}
//--------------------------------------------------------------------------
// Loop Statements
//--------------------------------------------------------------------------
/**
* Creates a context object of a loop statement and stacks it.
* @param {string} type The type of the node which was triggered. One of
* `WhileStatement`, `DoWhileStatement`, `ForStatement`, `ForInStatement`,
* and `ForStatement`.
* @param {string|null} label A label of the node which was triggered.
* @throws {Error} (Unreachable - unknown type.)
* @returns {void}
*/
pushLoopContext(type, label) {
const forkContext = this.forkContext;
// All loops need a path to account for `break` statements
const breakContext = this.pushBreakContext(true, label);
switch (type) {
case "WhileStatement":
this.pushChoiceContext("loop", false);
this.loopContext = new WhileLoopContext(this.loopContext, label, breakContext);
break;
case "DoWhileStatement":
this.pushChoiceContext("loop", false);
this.loopContext = new DoWhileLoopContext(this.loopContext, label, breakContext, forkContext);
break;
case "ForStatement":
this.pushChoiceContext("loop", false);
this.loopContext = new ForLoopContext(this.loopContext, label, breakContext);
break;
case "ForInStatement":
this.loopContext = new ForInLoopContext(this.loopContext, label, breakContext);
break;
case "ForOfStatement":
this.loopContext = new ForOfLoopContext(this.loopContext, label, breakContext);
break;
/* c8 ignore next */
default:
throw new Error(`unknown type: "${type}"`);
}
}
/**
* Pops the last context of a loop statement and finalizes it.
* @throws {Error} (Unreachable - unknown type.)
* @returns {void}
*/
popLoopContext() {
const context = this.loopContext;
this.loopContext = context.upper;
const forkContext = this.forkContext;
const brokenForkContext = this.popBreakContext().brokenForkContext;
// Creates a looped path.
switch (context.type) {
case "WhileStatement":
case "ForStatement":
this.popChoiceContext();
/*
* Creates the path from the end of the loop body up to the
* location where `continue` would jump to.
*/
makeLooped(
this,
forkContext.head,
context.continueDestSegments
);
break;
case "DoWhileStatement": {
const choiceContext = this.popChoiceContext();
if (!choiceContext.processed) {
choiceContext.trueForkContext.add(forkContext.head);
choiceContext.falseForkContext.add(forkContext.head);
}
/*
* If this isn't a hardcoded `true` condition, then `break`
* should continue down the path as if the condition evaluated
* to false.
*/
if (context.test !== true) {
brokenForkContext.addAll(choiceContext.falseForkContext);
}
/*
* When the condition is true, the loop continues back to the top,
* so create a path from each possible true condition back to the
* top of the loop.
*/
const segmentsList = choiceContext.trueForkContext.segmentsList;
for (let i = 0; i < segmentsList.length; ++i) {
makeLooped(
this,
segmentsList[i],
context.entrySegments
);
}
break;
}
case "ForInStatement":
case "ForOfStatement":
brokenForkContext.add(forkContext.head);
/*
* Creates the path from the end of the loop body up to the
* left expression (left of `in` or `of`) of the loop.
*/
makeLooped(
this,
forkContext.head,
context.leftSegments
);
break;
/* c8 ignore next */
default:
throw new Error("unreachable");
}
/*
* If there wasn't a `break` statement in the loop, then we're at
* the end of the loop's path, so we make an unreachable segment
* to mark that.
*
* If there was a `break` statement, then we continue on into the
* `brokenForkContext`.
*/
if (brokenForkContext.empty) {
forkContext.replaceHead(forkContext.makeUnreachable(-1, -1));
} else {
forkContext.replaceHead(brokenForkContext.makeNext(0, -1));
}
}
/**
* Makes a code path segment for the test part of a WhileStatement.
* @param {boolean|undefined} test The test value (only when constant).
* @returns {void}
*/
makeWhileTest(test) {
const context = this.loopContext;
const forkContext = this.forkContext;
const testSegments = forkContext.makeNext(0, -1);
// Update state.
context.test = test;
context.continueDestSegments = testSegments;
forkContext.replaceHead(testSegments);
}
/**
* Makes a code path segment for the body part of a WhileStatement.
* @returns {void}
*/
makeWhileBody() {
const context = this.loopContext;
const choiceContext = this.choiceContext;
const forkContext = this.forkContext;
if (!choiceContext.processed) {
choiceContext.trueForkContext.add(forkContext.head);
choiceContext.falseForkContext.add(forkContext.head);
}
/*
* If this isn't a hardcoded `true` condition, then `break`
* should continue down the path as if the condition evaluated
* to false.
*/
if (context.test !== true) {
context.brokenForkContext.addAll(choiceContext.falseForkContext);
}
forkContext.replaceHead(choiceContext.trueForkContext.makeNext(0, -1));
}
/**
* Makes a code path segment for the body part of a DoWhileStatement.
* @returns {void}
*/
makeDoWhileBody() {
const context = this.loopContext;
const forkContext = this.forkContext;
const bodySegments = forkContext.makeNext(-1, -1);
// Update state.
context.entrySegments = bodySegments;
forkContext.replaceHead(bodySegments);
}
/**
* Makes a code path segment for the test part of a DoWhileStatement.
* @param {boolean|undefined} test The test value (only when constant).
* @returns {void}
*/
makeDoWhileTest(test) {
const context = this.loopContext;
const forkContext = this.forkContext;
context.test = test;
/*
* If there is a `continue` statement in the loop then `continueForkContext`
* won't be empty. We wire up the path from `continue` to the loop
* test condition and then continue the traversal in the root fork context.
*/
if (!context.continueForkContext.empty) {
context.continueForkContext.add(forkContext.head);
const testSegments = context.continueForkContext.makeNext(0, -1);
forkContext.replaceHead(testSegments);
}
}
/**
* Makes a code path segment for the test part of a ForStatement.
* @param {boolean|undefined} test The test value (only when constant).
* @returns {void}
*/
makeForTest(test) {
const context = this.loopContext;
const forkContext = this.forkContext;
const endOfInitSegments = forkContext.head;
const testSegments = forkContext.makeNext(-1, -1);
/*
* Update the state.
*
* The `continueDestSegments` are set to `testSegments` because we
* don't yet know if there is an update expression in this loop. So,
* from what we already know at this point, a `continue` statement
* will jump back to the test expression.
*/
context.test = test;
context.endOfInitSegments = endOfInitSegments;
context.continueDestSegments = context.testSegments = testSegments;
forkContext.replaceHead(testSegments);
}
/**
* Makes a code path segment for the update part of a ForStatement.
* @returns {void}
*/
makeForUpdate() {
const context = this.loopContext;
const choiceContext = this.choiceContext;
const forkContext = this.forkContext;
// Make the next paths of the test.
if (context.testSegments) {
finalizeTestSegmentsOfFor(
context,
choiceContext,
forkContext.head
);
} else {
context.endOfInitSegments = forkContext.head;
}
/*
* Update the state.
*
* The `continueDestSegments` are now set to `updateSegments` because we
* know there is an update expression in this loop. So, a `continue` statement
* in the loop will jump to the update expression first, and then to any
* test expression the loop might have.
*/
const updateSegments = forkContext.makeDisconnected(-1, -1);
context.continueDestSegments = context.updateSegments = updateSegments;
forkContext.replaceHead(updateSegments);
}
/**
* Makes a code path segment for the body part of a ForStatement.
* @returns {void}
*/
makeForBody() {
const context = this.loopContext;
const choiceContext = this.choiceContext;
const forkContext = this.forkContext;
/*
* Determine what to do based on which part of the `for` loop are present.
* 1. If there is an update expression, then `updateSegments` is not null and
* we need to assign `endOfUpdateSegments`, and if there is a test
* expression, we then need to create the looped path to get back to
* the test condition.
* 2. If there is no update expression but there is a test expression,
* then we only need to update the test segment information.
* 3. If there is no update expression and no test expression, then we
* just save `endOfInitSegments`.
*/
if (context.updateSegments) {
context.endOfUpdateSegments = forkContext.head;
/*
* In a `for` loop that has both an update expression and a test
* condition, execution flows from the test expression into the
* loop body, to the update expression, and then back to the test
* expression to determine if the loop should continue.
*
* To account for that, we need to make a path from the end of the
* update expression to the start of the test expression. This is
* effectively what creates the loop in the code path.
*/
if (context.testSegments) {
makeLooped(
this,
context.endOfUpdateSegments,
context.testSegments
);
}
} else if (context.testSegments) {
finalizeTestSegmentsOfFor(
context,
choiceContext,
forkContext.head
);
} else {
context.endOfInitSegments = forkContext.head;
}
let bodySegments = context.endOfTestSegments;
/*
* If there is a test condition, then there `endOfTestSegments` is also
* the start of the loop body. If there isn't a test condition then
* `bodySegments` will be null and we need to look elsewhere to find
* the start of the body.
*
* The body starts at the end of the init expression and ends at the end
* of the update expression, so we use those locations to determine the
* body segments.
*/
if (!bodySegments) {
const prevForkContext = ForkContext.newEmpty(forkContext);
prevForkContext.add(context.endOfInitSegments);
if (context.endOfUpdateSegments) {
prevForkContext.add(context.endOfUpdateSegments);
}
bodySegments = prevForkContext.makeNext(0, -1);
}
/*
* If there was no test condition and no update expression, then
* `continueDestSegments` will be null. In that case, a
* `continue` should skip directly to the body of the loop.
* Otherwise, we want to keep the current `continueDestSegments`.
*/
context.continueDestSegments = context.continueDestSegments || bodySegments;
// move pointer to the body
forkContext.replaceHead(bodySegments);
}
/**
* Makes a code path segment for the left part of a ForInStatement and a
* ForOfStatement.
* @returns {void}
*/
makeForInOfLeft() {
const context = this.loopContext;
const forkContext = this.forkContext;
const leftSegments = forkContext.makeDisconnected(-1, -1);
// Update state.
context.prevSegments = forkContext.head;
context.leftSegments = context.continueDestSegments = leftSegments;
forkContext.replaceHead(leftSegments);
}
/**
* Makes a code path segment for the right part of a ForInStatement and a
* ForOfStatement.
* @returns {void}
*/
makeForInOfRight() {
const context = this.loopContext;
const forkContext = this.forkContext;
const temp = ForkContext.newEmpty(forkContext);
temp.add(context.prevSegments);
const rightSegments = temp.makeNext(-1, -1);
// Update state.
context.endOfLeftSegments = forkContext.head;
forkContext.replaceHead(rightSegments);
}
/**
* Makes a code path segment for the body part of a ForInStatement and a
* ForOfStatement.
* @returns {void}
*/
makeForInOfBody() {
const context = this.loopContext;
const forkContext = this.forkContext;
const temp = ForkContext.newEmpty(forkContext);
temp.add(context.endOfLeftSegments);
const bodySegments = temp.makeNext(-1, -1);
// Make a path: `right` -> `left`.
makeLooped(this, forkContext.head, context.leftSegments);
// Update state.
context.brokenForkContext.add(forkContext.head);
forkContext.replaceHead(bodySegments);
}
//--------------------------------------------------------------------------
// Control Statements
//--------------------------------------------------------------------------
/**
* Creates new context in which a `break` statement can be used. This occurs inside of a loop,
* labeled statement, or switch statement.
* @param {boolean} breakable Indicates if we are inside a statement where
* `break` without a label will exit the statement.
* @param {string|null} label The label associated with the statement.
* @returns {BreakContext} The new context.
*/
pushBreakContext(breakable, label) {
this.breakContext = new BreakContext(this.breakContext, breakable, label, this.forkContext);
return this.breakContext;
}
/**
* Removes the top item of the break context stack.
* @returns {Object} The removed context.
*/
popBreakContext() {
const context = this.breakContext;
const forkContext = this.forkContext;
this.breakContext = context.upper;
// Process this context here for other than switches and loops.
if (!context.breakable) {
const brokenForkContext = context.brokenForkContext;
if (!brokenForkContext.empty) {
brokenForkContext.add(forkContext.head);
forkContext.replaceHead(brokenForkContext.makeNext(0, -1));
}
}
return context;
}
/**
* Makes a path for a `break` statement.
*
* It registers the head segment to a context of `break`.
* It makes new unreachable segment, then it set the head with the segment.
* @param {string|null} label A label of the break statement.
* @returns {void}
*/
makeBreak(label) {
const forkContext = this.forkContext;
if (!forkContext.reachable) {
return;
}
const context = getBreakContext(this, label);
if (context) {
context.brokenForkContext.add(forkContext.head);
}
/* c8 ignore next */
forkContext.replaceHead(forkContext.makeUnreachable(-1, -1));
}
/**
* Makes a path for a `continue` statement.
*
* It makes a looping path.
* It makes new unreachable segment, then it set the head with the segment.
* @param {string|null} label A label of the continue statement.
* @returns {void}
*/
makeContinue(label) {
const forkContext = this.forkContext;
if (!forkContext.reachable) {
return;
}
const context = getContinueContext(this, label);
if (context) {
if (context.continueDestSegments) {
makeLooped(this, forkContext.head, context.continueDestSegments);
// If the context is a for-in/of loop, this affects a break also.
if (context.type === "ForInStatement" ||
context.type === "ForOfStatement"
) {
context.brokenForkContext.add(forkContext.head);
}
} else {
context.continueForkContext.add(forkContext.head);
}
}
forkContext.replaceHead(forkContext.makeUnreachable(-1, -1));
}
/**
* Makes a path for a `return` statement.
*
* It registers the head segment to a context of `return`.
* It makes new unreachable segment, then it set the head with the segment.
* @returns {void}
*/
makeReturn() {
const forkContext = this.forkContext;
if (forkContext.reachable) {
getReturnContext(this).returnedForkContext.add(forkContext.head);
forkContext.replaceHead(forkContext.makeUnreachable(-1, -1));
}
}
/**
* Makes a path for a `throw` statement.
*
* It registers the head segment to a context of `throw`.
* It makes new unreachable segment, then it set the head with the segment.
* @returns {void}
*/
makeThrow() {
const forkContext = this.forkContext;
if (forkContext.reachable) {
getThrowContext(this).thrownForkContext.add(forkContext.head);
forkContext.replaceHead(forkContext.makeUnreachable(-1, -1));
}
}
/**
* Makes the final path.
* @returns {void}
*/
makeFinal() {
const segments = this.currentSegments;
if (segments.length > 0 && segments[0].reachable) {
this.returnedForkContext.add(segments);
}
}
}
module.exports = CodePathState;