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219 lines
6.4 KiB
219 lines
6.4 KiB
3 years ago
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/**
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* @fileoverview Checks for unreachable code due to return, throws, break, and continue.
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* @author Joel Feenstra
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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/**
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* Checks whether or not a given variable declarator has the initializer.
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* @param {ASTNode} node A VariableDeclarator node to check.
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* @returns {boolean} `true` if the node has the initializer.
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*/
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function isInitialized(node) {
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return Boolean(node.init);
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}
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/**
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* Checks whether or not a given code path segment is unreachable.
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* @param {CodePathSegment} segment A CodePathSegment to check.
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* @returns {boolean} `true` if the segment is unreachable.
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*/
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function isUnreachable(segment) {
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return !segment.reachable;
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}
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/**
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* The class to distinguish consecutive unreachable statements.
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*/
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class ConsecutiveRange {
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constructor(sourceCode) {
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this.sourceCode = sourceCode;
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this.startNode = null;
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this.endNode = null;
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}
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/**
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* The location object of this range.
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* @type {Object}
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*/
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get location() {
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return {
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start: this.startNode.loc.start,
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end: this.endNode.loc.end
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};
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}
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/**
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* `true` if this range is empty.
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* @type {boolean}
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*/
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get isEmpty() {
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return !(this.startNode && this.endNode);
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}
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/**
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* Checks whether the given node is inside of this range.
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* @param {ASTNode|Token} node The node to check.
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* @returns {boolean} `true` if the node is inside of this range.
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*/
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contains(node) {
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return (
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node.range[0] >= this.startNode.range[0] &&
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node.range[1] <= this.endNode.range[1]
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);
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}
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/**
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* Checks whether the given node is consecutive to this range.
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* @param {ASTNode} node The node to check.
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* @returns {boolean} `true` if the node is consecutive to this range.
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*/
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isConsecutive(node) {
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return this.contains(this.sourceCode.getTokenBefore(node));
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}
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/**
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* Merges the given node to this range.
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* @param {ASTNode} node The node to merge.
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* @returns {void}
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*/
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merge(node) {
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this.endNode = node;
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}
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/**
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* Resets this range by the given node or null.
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* @param {ASTNode|null} node The node to reset, or null.
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* @returns {void}
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*/
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reset(node) {
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this.startNode = this.endNode = node;
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}
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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meta: {
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type: "problem",
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docs: {
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description: "disallow unreachable code after `return`, `throw`, `continue`, and `break` statements",
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category: "Possible Errors",
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recommended: true,
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url: "https://eslint.org/docs/rules/no-unreachable"
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},
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schema: [],
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messages: {
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unreachableCode: "Unreachable code."
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}
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},
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create(context) {
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let currentCodePath = null;
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const range = new ConsecutiveRange(context.getSourceCode());
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/**
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* Reports a given node if it's unreachable.
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* @param {ASTNode} node A statement node to report.
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* @returns {void}
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*/
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function reportIfUnreachable(node) {
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let nextNode = null;
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if (node && currentCodePath.currentSegments.every(isUnreachable)) {
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// Store this statement to distinguish consecutive statements.
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if (range.isEmpty) {
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range.reset(node);
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return;
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}
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// Skip if this statement is inside of the current range.
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if (range.contains(node)) {
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return;
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}
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// Merge if this statement is consecutive to the current range.
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if (range.isConsecutive(node)) {
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range.merge(node);
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return;
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}
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nextNode = node;
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}
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/*
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* Report the current range since this statement is reachable or is
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* not consecutive to the current range.
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*/
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if (!range.isEmpty) {
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context.report({
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messageId: "unreachableCode",
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loc: range.location,
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node: range.startNode
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});
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}
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// Update the current range.
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range.reset(nextNode);
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}
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return {
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// Manages the current code path.
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onCodePathStart(codePath) {
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currentCodePath = codePath;
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},
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onCodePathEnd() {
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currentCodePath = currentCodePath.upper;
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},
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// Registers for all statement nodes (excludes FunctionDeclaration).
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BlockStatement: reportIfUnreachable,
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BreakStatement: reportIfUnreachable,
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ClassDeclaration: reportIfUnreachable,
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ContinueStatement: reportIfUnreachable,
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DebuggerStatement: reportIfUnreachable,
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DoWhileStatement: reportIfUnreachable,
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ExpressionStatement: reportIfUnreachable,
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ForInStatement: reportIfUnreachable,
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ForOfStatement: reportIfUnreachable,
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ForStatement: reportIfUnreachable,
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IfStatement: reportIfUnreachable,
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ImportDeclaration: reportIfUnreachable,
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LabeledStatement: reportIfUnreachable,
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ReturnStatement: reportIfUnreachable,
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SwitchStatement: reportIfUnreachable,
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ThrowStatement: reportIfUnreachable,
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TryStatement: reportIfUnreachable,
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VariableDeclaration(node) {
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if (node.kind !== "var" || node.declarations.some(isInitialized)) {
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reportIfUnreachable(node);
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}
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},
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WhileStatement: reportIfUnreachable,
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WithStatement: reportIfUnreachable,
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ExportNamedDeclaration: reportIfUnreachable,
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ExportDefaultDeclaration: reportIfUnreachable,
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ExportAllDeclaration: reportIfUnreachable,
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"Program:exit"() {
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reportIfUnreachable();
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}
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};
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}
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};
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