Initial import with skill sheet working

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2024-12-04 00:11:23 +01:00
commit 9050c80ab4
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/**
* @fileoverview A class of the code path analyzer.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const assert = require("../../shared/assert"),
{ breakableTypePattern } = require("../../shared/ast-utils"),
CodePath = require("./code-path"),
CodePathSegment = require("./code-path-segment"),
IdGenerator = require("./id-generator"),
debug = require("./debug-helpers");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Checks whether or not a given node is a `case` node (not `default` node).
* @param {ASTNode} node A `SwitchCase` node to check.
* @returns {boolean} `true` if the node is a `case` node (not `default` node).
*/
function isCaseNode(node) {
return Boolean(node.test);
}
/**
* Checks if a given node appears as the value of a PropertyDefinition node.
* @param {ASTNode} node THe node to check.
* @returns {boolean} `true` if the node is a PropertyDefinition value,
* false if not.
*/
function isPropertyDefinitionValue(node) {
const parent = node.parent;
return parent && parent.type === "PropertyDefinition" && parent.value === node;
}
/**
* Checks whether the given logical operator is taken into account for the code
* path analysis.
* @param {string} operator The operator found in the LogicalExpression node
* @returns {boolean} `true` if the operator is "&&" or "||" or "??"
*/
function isHandledLogicalOperator(operator) {
return operator === "&&" || operator === "||" || operator === "??";
}
/**
* Checks whether the given assignment operator is a logical assignment operator.
* Logical assignments are taken into account for the code path analysis
* because of their short-circuiting semantics.
* @param {string} operator The operator found in the AssignmentExpression node
* @returns {boolean} `true` if the operator is "&&=" or "||=" or "??="
*/
function isLogicalAssignmentOperator(operator) {
return operator === "&&=" || operator === "||=" || operator === "??=";
}
/**
* Gets the label if the parent node of a given node is a LabeledStatement.
* @param {ASTNode} node A node to get.
* @returns {string|null} The label or `null`.
*/
function getLabel(node) {
if (node.parent.type === "LabeledStatement") {
return node.parent.label.name;
}
return null;
}
/**
* Checks whether or not a given logical expression node goes different path
* between the `true` case and the `false` case.
* @param {ASTNode} node A node to check.
* @returns {boolean} `true` if the node is a test of a choice statement.
*/
function isForkingByTrueOrFalse(node) {
const parent = node.parent;
switch (parent.type) {
case "ConditionalExpression":
case "IfStatement":
case "WhileStatement":
case "DoWhileStatement":
case "ForStatement":
return parent.test === node;
case "LogicalExpression":
return isHandledLogicalOperator(parent.operator);
case "AssignmentExpression":
return isLogicalAssignmentOperator(parent.operator);
default:
return false;
}
}
/**
* Gets the boolean value of a given literal node.
*
* This is used to detect infinity loops (e.g. `while (true) {}`).
* Statements preceded by an infinity loop are unreachable if the loop didn't
* have any `break` statement.
* @param {ASTNode} node A node to get.
* @returns {boolean|undefined} a boolean value if the node is a Literal node,
* otherwise `undefined`.
*/
function getBooleanValueIfSimpleConstant(node) {
if (node.type === "Literal") {
return Boolean(node.value);
}
return void 0;
}
/**
* Checks that a given identifier node is a reference or not.
*
* This is used to detect the first throwable node in a `try` block.
* @param {ASTNode} node An Identifier node to check.
* @returns {boolean} `true` if the node is a reference.
*/
function isIdentifierReference(node) {
const parent = node.parent;
switch (parent.type) {
case "LabeledStatement":
case "BreakStatement":
case "ContinueStatement":
case "ArrayPattern":
case "RestElement":
case "ImportSpecifier":
case "ImportDefaultSpecifier":
case "ImportNamespaceSpecifier":
case "CatchClause":
return false;
case "FunctionDeclaration":
case "FunctionExpression":
case "ArrowFunctionExpression":
case "ClassDeclaration":
case "ClassExpression":
case "VariableDeclarator":
return parent.id !== node;
case "Property":
case "PropertyDefinition":
case "MethodDefinition":
return (
parent.key !== node ||
parent.computed ||
parent.shorthand
);
case "AssignmentPattern":
return parent.key !== node;
default:
return true;
}
}
/**
* Updates the current segment with the head segment.
* This is similar to local branches and tracking branches of git.
*
* To separate the current and the head is in order to not make useless segments.
*
* In this process, both "onCodePathSegmentStart" and "onCodePathSegmentEnd"
* events are fired.
* @param {CodePathAnalyzer} analyzer The instance.
* @param {ASTNode} node The current AST node.
* @returns {void}
*/
function forwardCurrentToHead(analyzer, node) {
const codePath = analyzer.codePath;
const state = CodePath.getState(codePath);
const currentSegments = state.currentSegments;
const headSegments = state.headSegments;
const end = Math.max(currentSegments.length, headSegments.length);
let i, currentSegment, headSegment;
// Fires leaving events.
for (i = 0; i < end; ++i) {
currentSegment = currentSegments[i];
headSegment = headSegments[i];
if (currentSegment !== headSegment && currentSegment) {
const eventName = currentSegment.reachable
? "onCodePathSegmentEnd"
: "onUnreachableCodePathSegmentEnd";
debug.dump(`${eventName} ${currentSegment.id}`);
analyzer.emitter.emit(
eventName,
currentSegment,
node
);
}
}
// Update state.
state.currentSegments = headSegments;
// Fires entering events.
for (i = 0; i < end; ++i) {
currentSegment = currentSegments[i];
headSegment = headSegments[i];
if (currentSegment !== headSegment && headSegment) {
const eventName = headSegment.reachable
? "onCodePathSegmentStart"
: "onUnreachableCodePathSegmentStart";
debug.dump(`${eventName} ${headSegment.id}`);
CodePathSegment.markUsed(headSegment);
analyzer.emitter.emit(
eventName,
headSegment,
node
);
}
}
}
/**
* Updates the current segment with empty.
* This is called at the last of functions or the program.
* @param {CodePathAnalyzer} analyzer The instance.
* @param {ASTNode} node The current AST node.
* @returns {void}
*/
function leaveFromCurrentSegment(analyzer, node) {
const state = CodePath.getState(analyzer.codePath);
const currentSegments = state.currentSegments;
for (let i = 0; i < currentSegments.length; ++i) {
const currentSegment = currentSegments[i];
const eventName = currentSegment.reachable
? "onCodePathSegmentEnd"
: "onUnreachableCodePathSegmentEnd";
debug.dump(`${eventName} ${currentSegment.id}`);
analyzer.emitter.emit(
eventName,
currentSegment,
node
);
}
state.currentSegments = [];
}
/**
* Updates the code path due to the position of a given node in the parent node
* thereof.
*
* For example, if the node is `parent.consequent`, this creates a fork from the
* current path.
* @param {CodePathAnalyzer} analyzer The instance.
* @param {ASTNode} node The current AST node.
* @returns {void}
*/
function preprocess(analyzer, node) {
const codePath = analyzer.codePath;
const state = CodePath.getState(codePath);
const parent = node.parent;
switch (parent.type) {
// The `arguments.length == 0` case is in `postprocess` function.
case "CallExpression":
if (parent.optional === true && parent.arguments.length >= 1 && parent.arguments[0] === node) {
state.makeOptionalRight();
}
break;
case "MemberExpression":
if (parent.optional === true && parent.property === node) {
state.makeOptionalRight();
}
break;
case "LogicalExpression":
if (
parent.right === node &&
isHandledLogicalOperator(parent.operator)
) {
state.makeLogicalRight();
}
break;
case "AssignmentExpression":
if (
parent.right === node &&
isLogicalAssignmentOperator(parent.operator)
) {
state.makeLogicalRight();
}
break;
case "ConditionalExpression":
case "IfStatement":
/*
* Fork if this node is at `consequent`/`alternate`.
* `popForkContext()` exists at `IfStatement:exit` and
* `ConditionalExpression:exit`.
*/
if (parent.consequent === node) {
state.makeIfConsequent();
} else if (parent.alternate === node) {
state.makeIfAlternate();
}
break;
case "SwitchCase":
if (parent.consequent[0] === node) {
state.makeSwitchCaseBody(false, !parent.test);
}
break;
case "TryStatement":
if (parent.handler === node) {
state.makeCatchBlock();
} else if (parent.finalizer === node) {
state.makeFinallyBlock();
}
break;
case "WhileStatement":
if (parent.test === node) {
state.makeWhileTest(getBooleanValueIfSimpleConstant(node));
} else {
assert(parent.body === node);
state.makeWhileBody();
}
break;
case "DoWhileStatement":
if (parent.body === node) {
state.makeDoWhileBody();
} else {
assert(parent.test === node);
state.makeDoWhileTest(getBooleanValueIfSimpleConstant(node));
}
break;
case "ForStatement":
if (parent.test === node) {
state.makeForTest(getBooleanValueIfSimpleConstant(node));
} else if (parent.update === node) {
state.makeForUpdate();
} else if (parent.body === node) {
state.makeForBody();
}
break;
case "ForInStatement":
case "ForOfStatement":
if (parent.left === node) {
state.makeForInOfLeft();
} else if (parent.right === node) {
state.makeForInOfRight();
} else {
assert(parent.body === node);
state.makeForInOfBody();
}
break;
case "AssignmentPattern":
/*
* Fork if this node is at `right`.
* `left` is executed always, so it uses the current path.
* `popForkContext()` exists at `AssignmentPattern:exit`.
*/
if (parent.right === node) {
state.pushForkContext();
state.forkBypassPath();
state.forkPath();
}
break;
default:
break;
}
}
/**
* Updates the code path due to the type of a given node in entering.
* @param {CodePathAnalyzer} analyzer The instance.
* @param {ASTNode} node The current AST node.
* @returns {void}
*/
function processCodePathToEnter(analyzer, node) {
let codePath = analyzer.codePath;
let state = codePath && CodePath.getState(codePath);
const parent = node.parent;
/**
* Creates a new code path and trigger the onCodePathStart event
* based on the currently selected node.
* @param {string} origin The reason the code path was started.
* @returns {void}
*/
function startCodePath(origin) {
if (codePath) {
// Emits onCodePathSegmentStart events if updated.
forwardCurrentToHead(analyzer, node);
debug.dumpState(node, state, false);
}
// Create the code path of this scope.
codePath = analyzer.codePath = new CodePath({
id: analyzer.idGenerator.next(),
origin,
upper: codePath,
onLooped: analyzer.onLooped
});
state = CodePath.getState(codePath);
// Emits onCodePathStart events.
debug.dump(`onCodePathStart ${codePath.id}`);
analyzer.emitter.emit("onCodePathStart", codePath, node);
}
/*
* Special case: The right side of class field initializer is considered
* to be its own function, so we need to start a new code path in this
* case.
*/
if (isPropertyDefinitionValue(node)) {
startCodePath("class-field-initializer");
/*
* Intentional fall through because `node` needs to also be
* processed by the code below. For example, if we have:
*
* class Foo {
* a = () => {}
* }
*
* In this case, we also need start a second code path.
*/
}
switch (node.type) {
case "Program":
startCodePath("program");
break;
case "FunctionDeclaration":
case "FunctionExpression":
case "ArrowFunctionExpression":
startCodePath("function");
break;
case "StaticBlock":
startCodePath("class-static-block");
break;
case "ChainExpression":
state.pushChainContext();
break;
case "CallExpression":
if (node.optional === true) {
state.makeOptionalNode();
}
break;
case "MemberExpression":
if (node.optional === true) {
state.makeOptionalNode();
}
break;
case "LogicalExpression":
if (isHandledLogicalOperator(node.operator)) {
state.pushChoiceContext(
node.operator,
isForkingByTrueOrFalse(node)
);
}
break;
case "AssignmentExpression":
if (isLogicalAssignmentOperator(node.operator)) {
state.pushChoiceContext(
node.operator.slice(0, -1), // removes `=` from the end
isForkingByTrueOrFalse(node)
);
}
break;
case "ConditionalExpression":
case "IfStatement":
state.pushChoiceContext("test", false);
break;
case "SwitchStatement":
state.pushSwitchContext(
node.cases.some(isCaseNode),
getLabel(node)
);
break;
case "TryStatement":
state.pushTryContext(Boolean(node.finalizer));
break;
case "SwitchCase":
/*
* Fork if this node is after the 2st node in `cases`.
* It's similar to `else` blocks.
* The next `test` node is processed in this path.
*/
if (parent.discriminant !== node && parent.cases[0] !== node) {
state.forkPath();
}
break;
case "WhileStatement":
case "DoWhileStatement":
case "ForStatement":
case "ForInStatement":
case "ForOfStatement":
state.pushLoopContext(node.type, getLabel(node));
break;
case "LabeledStatement":
if (!breakableTypePattern.test(node.body.type)) {
state.pushBreakContext(false, node.label.name);
}
break;
default:
break;
}
// Emits onCodePathSegmentStart events if updated.
forwardCurrentToHead(analyzer, node);
debug.dumpState(node, state, false);
}
/**
* Updates the code path due to the type of a given node in leaving.
* @param {CodePathAnalyzer} analyzer The instance.
* @param {ASTNode} node The current AST node.
* @returns {void}
*/
function processCodePathToExit(analyzer, node) {
const codePath = analyzer.codePath;
const state = CodePath.getState(codePath);
let dontForward = false;
switch (node.type) {
case "ChainExpression":
state.popChainContext();
break;
case "IfStatement":
case "ConditionalExpression":
state.popChoiceContext();
break;
case "LogicalExpression":
if (isHandledLogicalOperator(node.operator)) {
state.popChoiceContext();
}
break;
case "AssignmentExpression":
if (isLogicalAssignmentOperator(node.operator)) {
state.popChoiceContext();
}
break;
case "SwitchStatement":
state.popSwitchContext();
break;
case "SwitchCase":
/*
* This is the same as the process at the 1st `consequent` node in
* `preprocess` function.
* Must do if this `consequent` is empty.
*/
if (node.consequent.length === 0) {
state.makeSwitchCaseBody(true, !node.test);
}
if (state.forkContext.reachable) {
dontForward = true;
}
break;
case "TryStatement":
state.popTryContext();
break;
case "BreakStatement":
forwardCurrentToHead(analyzer, node);
state.makeBreak(node.label && node.label.name);
dontForward = true;
break;
case "ContinueStatement":
forwardCurrentToHead(analyzer, node);
state.makeContinue(node.label && node.label.name);
dontForward = true;
break;
case "ReturnStatement":
forwardCurrentToHead(analyzer, node);
state.makeReturn();
dontForward = true;
break;
case "ThrowStatement":
forwardCurrentToHead(analyzer, node);
state.makeThrow();
dontForward = true;
break;
case "Identifier":
if (isIdentifierReference(node)) {
state.makeFirstThrowablePathInTryBlock();
dontForward = true;
}
break;
case "CallExpression":
case "ImportExpression":
case "MemberExpression":
case "NewExpression":
case "YieldExpression":
state.makeFirstThrowablePathInTryBlock();
break;
case "WhileStatement":
case "DoWhileStatement":
case "ForStatement":
case "ForInStatement":
case "ForOfStatement":
state.popLoopContext();
break;
case "AssignmentPattern":
state.popForkContext();
break;
case "LabeledStatement":
if (!breakableTypePattern.test(node.body.type)) {
state.popBreakContext();
}
break;
default:
break;
}
// Emits onCodePathSegmentStart events if updated.
if (!dontForward) {
forwardCurrentToHead(analyzer, node);
}
debug.dumpState(node, state, true);
}
/**
* Updates the code path to finalize the current code path.
* @param {CodePathAnalyzer} analyzer The instance.
* @param {ASTNode} node The current AST node.
* @returns {void}
*/
function postprocess(analyzer, node) {
/**
* Ends the code path for the current node.
* @returns {void}
*/
function endCodePath() {
let codePath = analyzer.codePath;
// Mark the current path as the final node.
CodePath.getState(codePath).makeFinal();
// Emits onCodePathSegmentEnd event of the current segments.
leaveFromCurrentSegment(analyzer, node);
// Emits onCodePathEnd event of this code path.
debug.dump(`onCodePathEnd ${codePath.id}`);
analyzer.emitter.emit("onCodePathEnd", codePath, node);
debug.dumpDot(codePath);
codePath = analyzer.codePath = analyzer.codePath.upper;
if (codePath) {
debug.dumpState(node, CodePath.getState(codePath), true);
}
}
switch (node.type) {
case "Program":
case "FunctionDeclaration":
case "FunctionExpression":
case "ArrowFunctionExpression":
case "StaticBlock": {
endCodePath();
break;
}
// The `arguments.length >= 1` case is in `preprocess` function.
case "CallExpression":
if (node.optional === true && node.arguments.length === 0) {
CodePath.getState(analyzer.codePath).makeOptionalRight();
}
break;
default:
break;
}
/*
* Special case: The right side of class field initializer is considered
* to be its own function, so we need to end a code path in this
* case.
*
* We need to check after the other checks in order to close the
* code paths in the correct order for code like this:
*
*
* class Foo {
* a = () => {}
* }
*
* In this case, The ArrowFunctionExpression code path is closed first
* and then we need to close the code path for the PropertyDefinition
* value.
*/
if (isPropertyDefinitionValue(node)) {
endCodePath();
}
}
//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
/**
* The class to analyze code paths.
* This class implements the EventGenerator interface.
*/
class CodePathAnalyzer {
/**
* @param {EventGenerator} eventGenerator An event generator to wrap.
*/
constructor(eventGenerator) {
this.original = eventGenerator;
this.emitter = eventGenerator.emitter;
this.codePath = null;
this.idGenerator = new IdGenerator("s");
this.currentNode = null;
this.onLooped = this.onLooped.bind(this);
}
/**
* Does the process to enter a given AST node.
* This updates state of analysis and calls `enterNode` of the wrapped.
* @param {ASTNode} node A node which is entering.
* @returns {void}
*/
enterNode(node) {
this.currentNode = node;
// Updates the code path due to node's position in its parent node.
if (node.parent) {
preprocess(this, node);
}
/*
* Updates the code path.
* And emits onCodePathStart/onCodePathSegmentStart events.
*/
processCodePathToEnter(this, node);
// Emits node events.
this.original.enterNode(node);
this.currentNode = null;
}
/**
* Does the process to leave a given AST node.
* This updates state of analysis and calls `leaveNode` of the wrapped.
* @param {ASTNode} node A node which is leaving.
* @returns {void}
*/
leaveNode(node) {
this.currentNode = node;
/*
* Updates the code path.
* And emits onCodePathStart/onCodePathSegmentStart events.
*/
processCodePathToExit(this, node);
// Emits node events.
this.original.leaveNode(node);
// Emits the last onCodePathStart/onCodePathSegmentStart events.
postprocess(this, node);
this.currentNode = null;
}
/**
* This is called on a code path looped.
* Then this raises a looped event.
* @param {CodePathSegment} fromSegment A segment of prev.
* @param {CodePathSegment} toSegment A segment of next.
* @returns {void}
*/
onLooped(fromSegment, toSegment) {
if (fromSegment.reachable && toSegment.reachable) {
debug.dump(`onCodePathSegmentLoop ${fromSegment.id} -> ${toSegment.id}`);
this.emitter.emit(
"onCodePathSegmentLoop",
fromSegment,
toSegment,
this.currentNode
);
}
}
}
module.exports = CodePathAnalyzer;

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/**
* @fileoverview The CodePathSegment class.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const debug = require("./debug-helpers");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Checks whether or not a given segment is reachable.
* @param {CodePathSegment} segment A segment to check.
* @returns {boolean} `true` if the segment is reachable.
*/
function isReachable(segment) {
return segment.reachable;
}
//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
/**
* A code path segment.
*
* Each segment is arranged in a series of linked lists (implemented by arrays)
* that keep track of the previous and next segments in a code path. In this way,
* you can navigate between all segments in any code path so long as you have a
* reference to any segment in that code path.
*
* When first created, the segment is in a detached state, meaning that it knows the
* segments that came before it but those segments don't know that this new segment
* follows it. Only when `CodePathSegment#markUsed()` is called on a segment does it
* officially become part of the code path by updating the previous segments to know
* that this new segment follows.
*/
class CodePathSegment {
/**
* Creates a new instance.
* @param {string} id An identifier.
* @param {CodePathSegment[]} allPrevSegments An array of the previous segments.
* This array includes unreachable segments.
* @param {boolean} reachable A flag which shows this is reachable.
*/
constructor(id, allPrevSegments, reachable) {
/**
* The identifier of this code path.
* Rules use it to store additional information of each rule.
* @type {string}
*/
this.id = id;
/**
* An array of the next reachable segments.
* @type {CodePathSegment[]}
*/
this.nextSegments = [];
/**
* An array of the previous reachable segments.
* @type {CodePathSegment[]}
*/
this.prevSegments = allPrevSegments.filter(isReachable);
/**
* An array of all next segments including reachable and unreachable.
* @type {CodePathSegment[]}
*/
this.allNextSegments = [];
/**
* An array of all previous segments including reachable and unreachable.
* @type {CodePathSegment[]}
*/
this.allPrevSegments = allPrevSegments;
/**
* A flag which shows this is reachable.
* @type {boolean}
*/
this.reachable = reachable;
// Internal data.
Object.defineProperty(this, "internal", {
value: {
// determines if the segment has been attached to the code path
used: false,
// array of previous segments coming from the end of a loop
loopedPrevSegments: []
}
});
/* c8 ignore start */
if (debug.enabled) {
this.internal.nodes = [];
}/* c8 ignore stop */
}
/**
* Checks a given previous segment is coming from the end of a loop.
* @param {CodePathSegment} segment A previous segment to check.
* @returns {boolean} `true` if the segment is coming from the end of a loop.
*/
isLoopedPrevSegment(segment) {
return this.internal.loopedPrevSegments.includes(segment);
}
/**
* Creates the root segment.
* @param {string} id An identifier.
* @returns {CodePathSegment} The created segment.
*/
static newRoot(id) {
return new CodePathSegment(id, [], true);
}
/**
* Creates a new segment and appends it after the given segments.
* @param {string} id An identifier.
* @param {CodePathSegment[]} allPrevSegments An array of the previous segments
* to append to.
* @returns {CodePathSegment} The created segment.
*/
static newNext(id, allPrevSegments) {
return new CodePathSegment(
id,
CodePathSegment.flattenUnusedSegments(allPrevSegments),
allPrevSegments.some(isReachable)
);
}
/**
* Creates an unreachable segment and appends it after the given segments.
* @param {string} id An identifier.
* @param {CodePathSegment[]} allPrevSegments An array of the previous segments.
* @returns {CodePathSegment} The created segment.
*/
static newUnreachable(id, allPrevSegments) {
const segment = new CodePathSegment(id, CodePathSegment.flattenUnusedSegments(allPrevSegments), false);
/*
* In `if (a) return a; foo();` case, the unreachable segment preceded by
* the return statement is not used but must not be removed.
*/
CodePathSegment.markUsed(segment);
return segment;
}
/**
* Creates a segment that follows given segments.
* This factory method does not connect with `allPrevSegments`.
* But this inherits `reachable` flag.
* @param {string} id An identifier.
* @param {CodePathSegment[]} allPrevSegments An array of the previous segments.
* @returns {CodePathSegment} The created segment.
*/
static newDisconnected(id, allPrevSegments) {
return new CodePathSegment(id, [], allPrevSegments.some(isReachable));
}
/**
* Marks a given segment as used.
*
* And this function registers the segment into the previous segments as a next.
* @param {CodePathSegment} segment A segment to mark.
* @returns {void}
*/
static markUsed(segment) {
if (segment.internal.used) {
return;
}
segment.internal.used = true;
let i;
if (segment.reachable) {
/*
* If the segment is reachable, then it's officially part of the
* code path. This loops through all previous segments to update
* their list of next segments. Because the segment is reachable,
* it's added to both `nextSegments` and `allNextSegments`.
*/
for (i = 0; i < segment.allPrevSegments.length; ++i) {
const prevSegment = segment.allPrevSegments[i];
prevSegment.allNextSegments.push(segment);
prevSegment.nextSegments.push(segment);
}
} else {
/*
* If the segment is not reachable, then it's not officially part of the
* code path. This loops through all previous segments to update
* their list of next segments. Because the segment is not reachable,
* it's added only to `allNextSegments`.
*/
for (i = 0; i < segment.allPrevSegments.length; ++i) {
segment.allPrevSegments[i].allNextSegments.push(segment);
}
}
}
/**
* Marks a previous segment as looped.
* @param {CodePathSegment} segment A segment.
* @param {CodePathSegment} prevSegment A previous segment to mark.
* @returns {void}
*/
static markPrevSegmentAsLooped(segment, prevSegment) {
segment.internal.loopedPrevSegments.push(prevSegment);
}
/**
* Creates a new array based on an array of segments. If any segment in the
* array is unused, then it is replaced by all of its previous segments.
* All used segments are returned as-is without replacement.
* @param {CodePathSegment[]} segments The array of segments to flatten.
* @returns {CodePathSegment[]} The flattened array.
*/
static flattenUnusedSegments(segments) {
const done = new Set();
for (let i = 0; i < segments.length; ++i) {
const segment = segments[i];
// Ignores duplicated.
if (done.has(segment)) {
continue;
}
// Use previous segments if unused.
if (!segment.internal.used) {
for (let j = 0; j < segment.allPrevSegments.length; ++j) {
const prevSegment = segment.allPrevSegments[j];
if (!done.has(prevSegment)) {
done.add(prevSegment);
}
}
} else {
done.add(segment);
}
}
return [...done];
}
}
module.exports = CodePathSegment;

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/**
* @fileoverview A class of the code path.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const CodePathState = require("./code-path-state");
const IdGenerator = require("./id-generator");
//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
/**
* A code path.
*/
class CodePath {
/**
* Creates a new instance.
* @param {Object} options Options for the function (see below).
* @param {string} options.id An identifier.
* @param {string} options.origin The type of code path origin.
* @param {CodePath|null} options.upper The code path of the upper function scope.
* @param {Function} options.onLooped A callback function to notify looping.
*/
constructor({ id, origin, upper, onLooped }) {
/**
* The identifier of this code path.
* Rules use it to store additional information of each rule.
* @type {string}
*/
this.id = id;
/**
* The reason that this code path was started. May be "program",
* "function", "class-field-initializer", or "class-static-block".
* @type {string}
*/
this.origin = origin;
/**
* The code path of the upper function scope.
* @type {CodePath|null}
*/
this.upper = upper;
/**
* The code paths of nested function scopes.
* @type {CodePath[]}
*/
this.childCodePaths = [];
// Initializes internal state.
Object.defineProperty(
this,
"internal",
{ value: new CodePathState(new IdGenerator(`${id}_`), onLooped) }
);
// Adds this into `childCodePaths` of `upper`.
if (upper) {
upper.childCodePaths.push(this);
}
}
/**
* Gets the state of a given code path.
* @param {CodePath} codePath A code path to get.
* @returns {CodePathState} The state of the code path.
*/
static getState(codePath) {
return codePath.internal;
}
/**
* The initial code path segment. This is the segment that is at the head
* of the code path.
* This is a passthrough to the underlying `CodePathState`.
* @type {CodePathSegment}
*/
get initialSegment() {
return this.internal.initialSegment;
}
/**
* Final code path segments. These are the terminal (tail) segments in the
* code path, which is the combination of `returnedSegments` and `thrownSegments`.
* All segments in this array are reachable.
* This is a passthrough to the underlying `CodePathState`.
* @type {CodePathSegment[]}
*/
get finalSegments() {
return this.internal.finalSegments;
}
/**
* Final code path segments that represent normal completion of the code path.
* For functions, this means both explicit `return` statements and implicit returns,
* such as the last reachable segment in a function that does not have an
* explicit `return` as this implicitly returns `undefined`. For scripts,
* modules, class field initializers, and class static blocks, this means
* all lines of code have been executed.
* These segments are also present in `finalSegments`.
* This is a passthrough to the underlying `CodePathState`.
* @type {CodePathSegment[]}
*/
get returnedSegments() {
return this.internal.returnedForkContext;
}
/**
* Final code path segments that represent `throw` statements.
* This is a passthrough to the underlying `CodePathState`.
* These segments are also present in `finalSegments`.
* @type {CodePathSegment[]}
*/
get thrownSegments() {
return this.internal.thrownForkContext;
}
/**
* Traverses all segments in this code path.
*
* codePath.traverseSegments((segment, controller) => {
* // do something.
* });
*
* This method enumerates segments in order from the head.
*
* The `controller` argument has two methods:
*
* - `skip()` - skips the following segments in this branch
* - `break()` - skips all following segments in the traversal
*
* A note on the parameters: the `options` argument is optional. This means
* the first argument might be an options object or the callback function.
* @param {Object} [optionsOrCallback] Optional first and last segments to traverse.
* @param {CodePathSegment} [optionsOrCallback.first] The first segment to traverse.
* @param {CodePathSegment} [optionsOrCallback.last] The last segment to traverse.
* @param {Function} callback A callback function.
* @returns {void}
*/
traverseSegments(optionsOrCallback, callback) {
// normalize the arguments into a callback and options
let resolvedOptions;
let resolvedCallback;
if (typeof optionsOrCallback === "function") {
resolvedCallback = optionsOrCallback;
resolvedOptions = {};
} else {
resolvedOptions = optionsOrCallback || {};
resolvedCallback = callback;
}
// determine where to start traversing from based on the options
const startSegment = resolvedOptions.first || this.internal.initialSegment;
const lastSegment = resolvedOptions.last;
// set up initial location information
let record;
let index;
let end;
let segment = null;
// segments that have already been visited during traversal
const visited = new Set();
// tracks the traversal steps
const stack = [[startSegment, 0]];
// segments that have been skipped during traversal
const skipped = new Set();
// indicates if we exited early from the traversal
let broken = false;
/**
* Maintains traversal state.
*/
const controller = {
/**
* Skip the following segments in this branch.
* @returns {void}
*/
skip() {
skipped.add(segment);
},
/**
* Stop traversal completely - do not traverse to any
* other segments.
* @returns {void}
*/
break() {
broken = true;
}
};
/**
* Checks if a given previous segment has been visited.
* @param {CodePathSegment} prevSegment A previous segment to check.
* @returns {boolean} `true` if the segment has been visited.
*/
function isVisited(prevSegment) {
return (
visited.has(prevSegment) ||
segment.isLoopedPrevSegment(prevSegment)
);
}
/**
* Checks if a given previous segment has been skipped.
* @param {CodePathSegment} prevSegment A previous segment to check.
* @returns {boolean} `true` if the segment has been skipped.
*/
function isSkipped(prevSegment) {
return (
skipped.has(prevSegment) ||
segment.isLoopedPrevSegment(prevSegment)
);
}
// the traversal
while (stack.length > 0) {
/*
* This isn't a pure stack. We use the top record all the time
* but don't always pop it off. The record is popped only if
* one of the following is true:
*
* 1) We have already visited the segment.
* 2) We have not visited *all* of the previous segments.
* 3) We have traversed past the available next segments.
*
* Otherwise, we just read the value and sometimes modify the
* record as we traverse.
*/
record = stack.at(-1);
segment = record[0];
index = record[1];
if (index === 0) {
// Skip if this segment has been visited already.
if (visited.has(segment)) {
stack.pop();
continue;
}
// Skip if all previous segments have not been visited.
if (segment !== startSegment &&
segment.prevSegments.length > 0 &&
!segment.prevSegments.every(isVisited)
) {
stack.pop();
continue;
}
visited.add(segment);
// Skips the segment if all previous segments have been skipped.
const shouldSkip = (
skipped.size > 0 &&
segment.prevSegments.length > 0 &&
segment.prevSegments.every(isSkipped)
);
/*
* If the most recent segment hasn't been skipped, then we call
* the callback, passing in the segment and the controller.
*/
if (!shouldSkip) {
resolvedCallback.call(this, segment, controller);
// exit if we're at the last segment
if (segment === lastSegment) {
controller.skip();
}
/*
* If the previous statement was executed, or if the callback
* called a method on the controller, we might need to exit the
* loop, so check for that and break accordingly.
*/
if (broken) {
break;
}
} else {
// If the most recent segment has been skipped, then mark it as skipped.
skipped.add(segment);
}
}
// Update the stack.
end = segment.nextSegments.length - 1;
if (index < end) {
/*
* If we haven't yet visited all of the next segments, update
* the current top record on the stack to the next index to visit
* and then push a record for the current segment on top.
*
* Setting the current top record's index lets us know how many
* times we've been here and ensures that the segment won't be
* reprocessed (because we only process segments with an index
* of 0).
*/
record[1] += 1;
stack.push([segment.nextSegments[index], 0]);
} else if (index === end) {
/*
* If we are at the last next segment, then reset the top record
* in the stack to next segment and set its index to 0 so it will
* be processed next.
*/
record[0] = segment.nextSegments[index];
record[1] = 0;
} else {
/*
* If index > end, that means we have no more segments that need
* processing. So, we pop that record off of the stack in order to
* continue traversing at the next level up.
*/
stack.pop();
}
}
}
}
module.exports = CodePath;

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/**
* @fileoverview Helpers to debug for code path analysis.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const debug = require("debug")("eslint:code-path");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Gets id of a given segment.
* @param {CodePathSegment} segment A segment to get.
* @returns {string} Id of the segment.
*/
/* c8 ignore next */
function getId(segment) { // eslint-disable-line jsdoc/require-jsdoc -- Ignoring
return segment.id + (segment.reachable ? "" : "!");
}
/**
* Get string for the given node and operation.
* @param {ASTNode} node The node to convert.
* @param {"enter" | "exit" | undefined} label The operation label.
* @returns {string} The string representation.
*/
function nodeToString(node, label) {
const suffix = label ? `:${label}` : "";
switch (node.type) {
case "Identifier": return `${node.type}${suffix} (${node.name})`;
case "Literal": return `${node.type}${suffix} (${node.value})`;
default: return `${node.type}${suffix}`;
}
}
//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
module.exports = {
/**
* A flag that debug dumping is enabled or not.
* @type {boolean}
*/
enabled: debug.enabled,
/**
* Dumps given objects.
* @param {...any} args objects to dump.
* @returns {void}
*/
dump: debug,
/**
* Dumps the current analyzing state.
* @param {ASTNode} node A node to dump.
* @param {CodePathState} state A state to dump.
* @param {boolean} leaving A flag whether or not it's leaving
* @returns {void}
*/
dumpState: !debug.enabled ? debug : /* c8 ignore next */ function(node, state, leaving) {
for (let i = 0; i < state.currentSegments.length; ++i) {
const segInternal = state.currentSegments[i].internal;
if (leaving) {
const last = segInternal.nodes.length - 1;
if (last >= 0 && segInternal.nodes[last] === nodeToString(node, "enter")) {
segInternal.nodes[last] = nodeToString(node, void 0);
} else {
segInternal.nodes.push(nodeToString(node, "exit"));
}
} else {
segInternal.nodes.push(nodeToString(node, "enter"));
}
}
debug([
`${state.currentSegments.map(getId).join(",")})`,
`${node.type}${leaving ? ":exit" : ""}`
].join(" "));
},
/**
* Dumps a DOT code of a given code path.
* The DOT code can be visualized with Graphvis.
* @param {CodePath} codePath A code path to dump.
* @returns {void}
* @see http://www.graphviz.org
* @see http://www.webgraphviz.com
*/
dumpDot: !debug.enabled ? debug : /* c8 ignore next */ function(codePath) {
let text =
"\n" +
"digraph {\n" +
"node[shape=box,style=\"rounded,filled\",fillcolor=white];\n" +
"initial[label=\"\",shape=circle,style=filled,fillcolor=black,width=0.25,height=0.25];\n";
if (codePath.returnedSegments.length > 0) {
text += "final[label=\"\",shape=doublecircle,style=filled,fillcolor=black,width=0.25,height=0.25];\n";
}
if (codePath.thrownSegments.length > 0) {
text += "thrown[label=\"✘\",shape=circle,width=0.3,height=0.3,fixedsize=true];\n";
}
const traceMap = Object.create(null);
const arrows = this.makeDotArrows(codePath, traceMap);
for (const id in traceMap) { // eslint-disable-line guard-for-in -- Want ability to traverse prototype
const segment = traceMap[id];
text += `${id}[`;
if (segment.reachable) {
text += "label=\"";
} else {
text += "style=\"rounded,dashed,filled\",fillcolor=\"#FF9800\",label=\"<<unreachable>>\\n";
}
if (segment.internal.nodes.length > 0) {
text += segment.internal.nodes.join("\\n");
} else {
text += "????";
}
text += "\"];\n";
}
text += `${arrows}\n`;
text += "}";
debug("DOT", text);
},
/**
* Makes a DOT code of a given code path.
* The DOT code can be visualized with Graphvis.
* @param {CodePath} codePath A code path to make DOT.
* @param {Object} traceMap Optional. A map to check whether or not segments had been done.
* @returns {string} A DOT code of the code path.
*/
makeDotArrows(codePath, traceMap) {
const stack = [[codePath.initialSegment, 0]];
const done = traceMap || Object.create(null);
let lastId = codePath.initialSegment.id;
let text = `initial->${codePath.initialSegment.id}`;
while (stack.length > 0) {
const item = stack.pop();
const segment = item[0];
const index = item[1];
if (done[segment.id] && index === 0) {
continue;
}
done[segment.id] = segment;
const nextSegment = segment.allNextSegments[index];
if (!nextSegment) {
continue;
}
if (lastId === segment.id) {
text += `->${nextSegment.id}`;
} else {
text += `;\n${segment.id}->${nextSegment.id}`;
}
lastId = nextSegment.id;
stack.unshift([segment, 1 + index]);
stack.push([nextSegment, 0]);
}
codePath.returnedSegments.forEach(finalSegment => {
if (lastId === finalSegment.id) {
text += "->final";
} else {
text += `;\n${finalSegment.id}->final`;
}
lastId = null;
});
codePath.thrownSegments.forEach(finalSegment => {
if (lastId === finalSegment.id) {
text += "->thrown";
} else {
text += `;\n${finalSegment.id}->thrown`;
}
lastId = null;
});
return `${text};`;
}
};

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/**
* @fileoverview A class to operate forking.
*
* This is state of forking.
* This has a fork list and manages it.
*
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const assert = require("../../shared/assert"),
CodePathSegment = require("./code-path-segment");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Determines whether or not a given segment is reachable.
* @param {CodePathSegment} segment The segment to check.
* @returns {boolean} `true` if the segment is reachable.
*/
function isReachable(segment) {
return segment.reachable;
}
/**
* Creates a new segment for each fork in the given context and appends it
* to the end of the specified range of segments. Ultimately, this ends up calling
* `new CodePathSegment()` for each of the forks using the `create` argument
* as a wrapper around special behavior.
*
* The `startIndex` and `endIndex` arguments specify a range of segments in
* `context` that should become `allPrevSegments` for the newly created
* `CodePathSegment` objects.
*
* When `context.segmentsList` is `[[a, b], [c, d], [e, f]]`, `begin` is `0`, and
* `end` is `-1`, this creates two new segments, `[g, h]`. This `g` is appended to
* the end of the path from `a`, `c`, and `e`. This `h` is appended to the end of
* `b`, `d`, and `f`.
* @param {ForkContext} context An instance from which the previous segments
* will be obtained.
* @param {number} startIndex The index of the first segment in the context
* that should be specified as previous segments for the newly created segments.
* @param {number} endIndex The index of the last segment in the context
* that should be specified as previous segments for the newly created segments.
* @param {Function} create A function that creates new `CodePathSegment`
* instances in a particular way. See the `CodePathSegment.new*` methods.
* @returns {Array<CodePathSegment>} An array of the newly-created segments.
*/
function createSegments(context, startIndex, endIndex, create) {
/** @type {Array<Array<CodePathSegment>>} */
const list = context.segmentsList;
/*
* Both `startIndex` and `endIndex` work the same way: if the number is zero
* or more, then the number is used as-is. If the number is negative,
* then that number is added to the length of the segments list to
* determine the index to use. That means -1 for either argument
* is the last element, -2 is the second to last, and so on.
*
* So if `startIndex` is 0, `endIndex` is -1, and `list.length` is 3, the
* effective `startIndex` is 0 and the effective `endIndex` is 2, so this function
* will include items at indices 0, 1, and 2.
*
* Therefore, if `startIndex` is -1 and `endIndex` is -1, that means we'll only
* be using the last segment in `list`.
*/
const normalizedBegin = startIndex >= 0 ? startIndex : list.length + startIndex;
const normalizedEnd = endIndex >= 0 ? endIndex : list.length + endIndex;
/** @type {Array<CodePathSegment>} */
const segments = [];
for (let i = 0; i < context.count; ++i) {
// this is passed into `new CodePathSegment` to add to code path.
const allPrevSegments = [];
for (let j = normalizedBegin; j <= normalizedEnd; ++j) {
allPrevSegments.push(list[j][i]);
}
// note: `create` is just a wrapper that augments `new CodePathSegment`.
segments.push(create(context.idGenerator.next(), allPrevSegments));
}
return segments;
}
/**
* Inside of a `finally` block we end up with two parallel paths. If the code path
* exits by a control statement (such as `break` or `continue`) from the `finally`
* block, then we need to merge the remaining parallel paths back into one.
* @param {ForkContext} context The fork context to work on.
* @param {Array<CodePathSegment>} segments Segments to merge.
* @returns {Array<CodePathSegment>} The merged segments.
*/
function mergeExtraSegments(context, segments) {
let currentSegments = segments;
/*
* We need to ensure that the array returned from this function contains no more
* than the number of segments that the context allows. `context.count` indicates
* how many items should be in the returned array to ensure that the new segment
* entries will line up with the already existing segment entries.
*/
while (currentSegments.length > context.count) {
const merged = [];
/*
* Because `context.count` is a factor of 2 inside of a `finally` block,
* we can divide the segment count by 2 to merge the paths together.
* This loops through each segment in the list and creates a new `CodePathSegment`
* that has the segment and the segment two slots away as previous segments.
*
* If `currentSegments` is [a,b,c,d], this will create new segments e and f, such
* that:
*
* When `i` is 0:
* a->e
* c->e
*
* When `i` is 1:
* b->f
* d->f
*/
for (let i = 0, length = Math.floor(currentSegments.length / 2); i < length; ++i) {
merged.push(CodePathSegment.newNext(
context.idGenerator.next(),
[currentSegments[i], currentSegments[i + length]]
));
}
/*
* Go through the loop condition one more time to see if we have the
* number of segments for the context. If not, we'll keep merging paths
* of the merged segments until we get there.
*/
currentSegments = merged;
}
return currentSegments;
}
//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
/**
* Manages the forking of code paths.
*/
class ForkContext {
/**
* Creates a new instance.
* @param {IdGenerator} idGenerator An identifier generator for segments.
* @param {ForkContext|null} upper The preceding fork context.
* @param {number} count The number of parallel segments in each element
* of `segmentsList`.
*/
constructor(idGenerator, upper, count) {
/**
* The ID generator that will generate segment IDs for any new
* segments that are created.
* @type {IdGenerator}
*/
this.idGenerator = idGenerator;
/**
* The preceding fork context.
* @type {ForkContext|null}
*/
this.upper = upper;
/**
* The number of elements in each element of `segmentsList`. In most
* cases, this is 1 but can be 2 when there is a `finally` present,
* which forks the code path outside of normal flow. In the case of nested
* `finally` blocks, this can be a multiple of 2.
* @type {number}
*/
this.count = count;
/**
* The segments within this context. Each element in this array has
* `count` elements that represent one step in each fork. For example,
* when `segmentsList` is `[[a, b], [c, d], [e, f]]`, there is one path
* a->c->e and one path b->d->f, and `count` is 2 because each element
* is an array with two elements.
* @type {Array<Array<CodePathSegment>>}
*/
this.segmentsList = [];
}
/**
* The segments that begin this fork context.
* @type {Array<CodePathSegment>}
*/
get head() {
const list = this.segmentsList;
return list.length === 0 ? [] : list.at(-1);
}
/**
* Indicates if the context contains no segments.
* @type {boolean}
*/
get empty() {
return this.segmentsList.length === 0;
}
/**
* Indicates if there are any segments that are reachable.
* @type {boolean}
*/
get reachable() {
const segments = this.head;
return segments.length > 0 && segments.some(isReachable);
}
/**
* Creates new segments in this context and appends them to the end of the
* already existing `CodePathSegment`s specified by `startIndex` and
* `endIndex`.
* @param {number} startIndex The index of the first segment in the context
* that should be specified as previous segments for the newly created segments.
* @param {number} endIndex The index of the last segment in the context
* that should be specified as previous segments for the newly created segments.
* @returns {Array<CodePathSegment>} An array of the newly created segments.
*/
makeNext(startIndex, endIndex) {
return createSegments(this, startIndex, endIndex, CodePathSegment.newNext);
}
/**
* Creates new unreachable segments in this context and appends them to the end of the
* already existing `CodePathSegment`s specified by `startIndex` and
* `endIndex`.
* @param {number} startIndex The index of the first segment in the context
* that should be specified as previous segments for the newly created segments.
* @param {number} endIndex The index of the last segment in the context
* that should be specified as previous segments for the newly created segments.
* @returns {Array<CodePathSegment>} An array of the newly created segments.
*/
makeUnreachable(startIndex, endIndex) {
return createSegments(this, startIndex, endIndex, CodePathSegment.newUnreachable);
}
/**
* Creates new segments in this context and does not append them to the end
* of the already existing `CodePathSegment`s specified by `startIndex` and
* `endIndex`. The `startIndex` and `endIndex` are only used to determine if
* the new segments should be reachable. If any of the segments in this range
* are reachable then the new segments are also reachable; otherwise, the new
* segments are unreachable.
* @param {number} startIndex The index of the first segment in the context
* that should be considered for reachability.
* @param {number} endIndex The index of the last segment in the context
* that should be considered for reachability.
* @returns {Array<CodePathSegment>} An array of the newly created segments.
*/
makeDisconnected(startIndex, endIndex) {
return createSegments(this, startIndex, endIndex, CodePathSegment.newDisconnected);
}
/**
* Adds segments to the head of this context.
* @param {Array<CodePathSegment>} segments The segments to add.
* @returns {void}
*/
add(segments) {
assert(segments.length >= this.count, `${segments.length} >= ${this.count}`);
this.segmentsList.push(mergeExtraSegments(this, segments));
}
/**
* Replaces the head segments with the given segments.
* The current head segments are removed.
* @param {Array<CodePathSegment>} replacementHeadSegments The new head segments.
* @returns {void}
*/
replaceHead(replacementHeadSegments) {
assert(
replacementHeadSegments.length >= this.count,
`${replacementHeadSegments.length} >= ${this.count}`
);
this.segmentsList.splice(-1, 1, mergeExtraSegments(this, replacementHeadSegments));
}
/**
* Adds all segments of a given fork context into this context.
* @param {ForkContext} otherForkContext The fork context to add from.
* @returns {void}
*/
addAll(otherForkContext) {
assert(otherForkContext.count === this.count);
this.segmentsList.push(...otherForkContext.segmentsList);
}
/**
* Clears all segments in this context.
* @returns {void}
*/
clear() {
this.segmentsList = [];
}
/**
* Creates a new root context, meaning that there are no parent
* fork contexts.
* @param {IdGenerator} idGenerator An identifier generator for segments.
* @returns {ForkContext} New fork context.
*/
static newRoot(idGenerator) {
const context = new ForkContext(idGenerator, null, 1);
context.add([CodePathSegment.newRoot(idGenerator.next())]);
return context;
}
/**
* Creates an empty fork context preceded by a given context.
* @param {ForkContext} parentContext The parent fork context.
* @param {boolean} shouldForkLeavingPath Indicates that we are inside of
* a `finally` block and should therefore fork the path that leaves
* `finally`.
* @returns {ForkContext} New fork context.
*/
static newEmpty(parentContext, shouldForkLeavingPath) {
return new ForkContext(
parentContext.idGenerator,
parentContext,
(shouldForkLeavingPath ? 2 : 1) * parentContext.count
);
}
}
module.exports = ForkContext;

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@ -0,0 +1,45 @@
/**
* @fileoverview A class of identifiers generator for code path segments.
*
* Each rule uses the identifier of code path segments to store additional
* information of the code path.
*
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
/**
* A generator for unique ids.
*/
class IdGenerator {
/**
* @param {string} prefix Optional. A prefix of generated ids.
*/
constructor(prefix) {
this.prefix = String(prefix);
this.n = 0;
}
/**
* Generates id.
* @returns {string} A generated id.
*/
next() {
this.n = 1 + this.n | 0;
/* c8 ignore start */
if (this.n < 0) {
this.n = 1;
}/* c8 ignore stop */
return this.prefix + this.n;
}
}
module.exports = IdGenerator;