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- "use strict";
- function createReferenceMap(scope, outReferenceMap = new Map()) {
- for (const reference of scope.references) {
- if (reference.resolved === null) {
- continue;
- }
- outReferenceMap.set(reference.identifier, reference);
- }
- for (const childScope of scope.childScopes) {
- if (childScope.type !== "function") {
- createReferenceMap(childScope, outReferenceMap);
- }
- }
- return outReferenceMap;
- }
- function getWriteExpr(reference) {
- if (reference.writeExpr) {
- return reference.writeExpr;
- }
- let node = reference.identifier;
- while (node) {
- const t = node.parent.type;
- if (t === "AssignmentExpression" && node.parent.left === node) {
- return node.parent.right;
- }
- if (t === "MemberExpression" && node.parent.object === node) {
- node = node.parent;
- continue;
- }
- break;
- }
- return null;
- }
- function isLocalVariableWithoutEscape(variable, isMemberAccess) {
- if (!variable) {
- return false;
- }
-
- if (isMemberAccess && variable.defs.some(d => d.type === "Parameter")) {
- return false;
- }
- const functionScope = variable.scope.variableScope;
- return variable.references.every(reference =>
- reference.from.variableScope === functionScope);
- }
- class SegmentInfo {
- constructor() {
- this.info = new WeakMap();
- }
-
- initialize(segment) {
- const outdatedReadVariables = new Set();
- const freshReadVariables = new Set();
- for (const prevSegment of segment.prevSegments) {
- const info = this.info.get(prevSegment);
- if (info) {
- info.outdatedReadVariables.forEach(Set.prototype.add, outdatedReadVariables);
- info.freshReadVariables.forEach(Set.prototype.add, freshReadVariables);
- }
- }
- this.info.set(segment, { outdatedReadVariables, freshReadVariables });
- }
-
- markAsRead(segments, variable) {
- for (const segment of segments) {
- const info = this.info.get(segment);
- if (info) {
- info.freshReadVariables.add(variable);
-
- info.outdatedReadVariables.delete(variable);
- }
- }
- }
-
- makeOutdated(segments) {
- for (const segment of segments) {
- const info = this.info.get(segment);
- if (info) {
- info.freshReadVariables.forEach(Set.prototype.add, info.outdatedReadVariables);
- info.freshReadVariables.clear();
- }
- }
- }
-
- isOutdated(segments, variable) {
- for (const segment of segments) {
- const info = this.info.get(segment);
- if (info && info.outdatedReadVariables.has(variable)) {
- return true;
- }
- }
- return false;
- }
- }
- module.exports = {
- meta: {
- type: "problem",
- docs: {
- description: "disallow assignments that can lead to race conditions due to usage of `await` or `yield`",
- category: "Possible Errors",
- recommended: false,
- url: "https://eslint.org/docs/rules/require-atomic-updates"
- },
- fixable: null,
- schema: [],
- messages: {
- nonAtomicUpdate: "Possible race condition: `{{value}}` might be reassigned based on an outdated value of `{{value}}`."
- }
- },
- create(context) {
- const sourceCode = context.getSourceCode();
- const assignmentReferences = new Map();
- const segmentInfo = new SegmentInfo();
- let stack = null;
- return {
- onCodePathStart(codePath) {
- const scope = context.getScope();
- const shouldVerify =
- scope.type === "function" &&
- (scope.block.async || scope.block.generator);
- stack = {
- upper: stack,
- codePath,
- referenceMap: shouldVerify ? createReferenceMap(scope) : null
- };
- },
- onCodePathEnd() {
- stack = stack.upper;
- },
-
- onCodePathSegmentStart(segment) {
- segmentInfo.initialize(segment);
- },
-
- Identifier(node) {
- const { codePath, referenceMap } = stack;
- const reference = referenceMap && referenceMap.get(node);
-
- if (!reference) {
- return;
- }
- const variable = reference.resolved;
- const writeExpr = getWriteExpr(reference);
- const isMemberAccess = reference.identifier.parent.type === "MemberExpression";
-
- if (reference.isRead() && !(writeExpr && writeExpr.parent.operator === "=")) {
- segmentInfo.markAsRead(codePath.currentSegments, variable);
- }
-
- if (writeExpr &&
- writeExpr.parent.right === writeExpr &&
- !isLocalVariableWithoutEscape(variable, isMemberAccess)
- ) {
- let refs = assignmentReferences.get(writeExpr);
- if (!refs) {
- refs = [];
- assignmentReferences.set(writeExpr, refs);
- }
- refs.push(reference);
- }
- },
-
- ":expression:exit"(node) {
- const { codePath, referenceMap } = stack;
-
- if (!referenceMap) {
- return;
- }
-
- if (node.type === "AwaitExpression" || node.type === "YieldExpression") {
- segmentInfo.makeOutdated(codePath.currentSegments);
- }
-
- const references = assignmentReferences.get(node);
- if (references) {
- assignmentReferences.delete(node);
- for (const reference of references) {
- const variable = reference.resolved;
- if (segmentInfo.isOutdated(codePath.currentSegments, variable)) {
- context.report({
- node: node.parent,
- messageId: "nonAtomicUpdate",
- data: {
- value: sourceCode.getText(node.parent.left)
- }
- });
- }
- }
- }
- }
- };
- }
- };
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