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Commit09bd7fe

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feat!: move AST traversal into SourceCode (#18167)
* feat: Implement SourceCode#traverse()Refs#16999* Add more debugging* Clean up sourcecode* Try to fix code paths* Fix rules and update migration guide* Cache traversal steps* Fix lint error* Fix fuzz test* Simplify TraversalStep constructor* Remove unused parent arg* Fix constructor-super
1 parentb91f9dc commit09bd7fe

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9 files changed

+334
-65
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9 files changed

+334
-65
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‎docs/src/use/migrate-to-9.0.0.md‎

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Original file line numberDiff line numberDiff line change
@@ -43,6 +43,7 @@ The lists below are ordered roughly by the number of users each change is expect
4343
*[Removed multiple`context` methods](#removed-context-methods)
4444
*[Removed`sourceCode.getComments()`](#removed-sourcecode-getcomments)
4545
*[Removed`CodePath#currentSegments`](#removed-codepath-currentsegments)
46+
*[Code paths are now precalculated](#codepath-precalc)
4647
*[Function-style rules are no longer supported](#drop-function-style-rules)
4748
*[`meta.schema` is required for rules with options](#meta-schema-required)
4849
*[`FlatRuleTester` is now`RuleTester`](#flat-rule-tester)
@@ -490,6 +491,19 @@ ESLint v9.0.0 removes the deprecated `CodePath#currentSegments` property.
490491

491492
**Related Issues(s):**[#17457](https://github.com/eslint/eslint/issues/17457)
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494+
##<aname="codepath-precalc"></a> Code paths are now precalculated
495+
496+
Prior to ESLint v9.0.0, code paths were calculated during the same AST traversal used by rules, meaning that the information passed to methods like`onCodePathStart` and`onCodePathSegmentStart` was incomplete. Specifically, array properties like`CodePath#childCodePaths` and`CodePathSegment#nextSegments` began empty and then were filled with the appropriate information as the traversal completed, meaning that those arrays could have different elements depending on when you checked their values.
497+
498+
ESLint v9.0.0 now precalculates code path information before the traversal used by rules. As a result, the code path information is now complete regardless of where it is accessed inside of a rule.
499+
500+
**To address:** If you are accessing any array properties on`CodePath` or`CodePathSegment`, you'll need to update your code. Specifically:
501+
502+
* If you are checking the`length` of any array properties, ensure you are using relative comparison operators like`<`,`>`,`<=`, and`>=` instead of equals.
503+
* If you are accessing the`nextSegments`,`prevSegments`,`allNextSegments`, or`allPrevSegments` properties on a`CodePathSegment`, or`CodePath#childCodePaths`, verify that your code will still work as expected. To be backwards compatible, consider moving the logic that checks these properties into`onCodePathEnd`.
504+
505+
**Related Issues(s):**[#16999](https://github.com/eslint/eslint/issues/16999)
506+
493507
##<aname="drop-function-style-rules"></a> Function-style rules are no longer supported
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495509
ESLint v9.0.0 drops support for function-style rules. Function-style rules are rules created by exporting a function rather than an object with a`create()` method. This rule format was deprecated in 2016.

‎lib/linter/code-path-analysis/code-path-analyzer.js‎

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Original file line numberDiff line numberDiff line change
@@ -222,7 +222,6 @@ function forwardCurrentToHead(analyzer, node) {
222222
:"onUnreachableCodePathSegmentStart";
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224224
debug.dump(`${eventName}${headSegment.id}`);
225-
226225
CodePathSegment.markUsed(headSegment);
227226
analyzer.emitter.emit(
228227
eventName,

‎lib/linter/linter.js‎

Lines changed: 30 additions & 29 deletions
Original file line numberDiff line numberDiff line change
@@ -30,7 +30,6 @@ const
3030
}=require("@eslint/eslintrc/universal"),
3131
Traverser=require("../shared/traverser"),
3232
{ SourceCode}=require("../source-code"),
33-
CodePathAnalyzer=require("./code-path-analysis/code-path-analyzer"),
3433
applyDisableDirectives=require("./apply-disable-directives"),
3534
ConfigCommentParser=require("./config-comment-parser"),
3635
NodeEventGenerator=require("./node-event-generator"),
@@ -53,6 +52,8 @@ const commentParser = new ConfigCommentParser();
5352
constDEFAULT_ERROR_LOC={start:{line:1,column:0},end:{line:1,column:1}};
5453
constparserSymbol=Symbol.for("eslint.RuleTester.parser");
5554
const{LATEST_ECMA_VERSION}=require("../../conf/ecma-version");
55+
constSTEP_KIND_VISIT=1;
56+
constSTEP_KIND_CALL=2;
5657

5758
//------------------------------------------------------------------------------
5859
// Typedefs
@@ -986,22 +987,13 @@ function createRuleListeners(rule, ruleContext) {
986987
*@param {string} physicalFilename The full path of the file on disk without any code block information
987988
*@param {Function} ruleFilter A predicate function to filter which rules should be executed.
988989
*@returns {LintMessage[]} An array of reported problems
990+
*@throws {Error} If traversal into a node fails.
989991
*/
990992
functionrunRules(sourceCode,configuredRules,ruleMapper,parserName,languageOptions,settings,filename,disableFixes,cwd,physicalFilename,ruleFilter){
991993
constemitter=createEmitter();
992-
constnodeQueue=[];
993-
letcurrentNode=sourceCode.ast;
994-
995-
Traverser.traverse(sourceCode.ast,{
996-
enter(node,parent){
997-
node.parent=parent;
998-
nodeQueue.push({isEntering:true, node});
999-
},
1000-
leave(node){
1001-
nodeQueue.push({isEntering:false, node});
1002-
},
1003-
visitorKeys:sourceCode.visitorKeys
1004-
});
994+
995+
// must happen first to assign all node.parent properties
996+
consteventQueue=sourceCode.traverse();
1005997

1006998
/*
1007999
* Create a frozen object with the ruleContext properties and methods that are shared by all rules.
@@ -1131,25 +1123,34 @@ function runRules(sourceCode, configuredRules, ruleMapper, parserName, languageO
11311123
});
11321124
});
11331125

1134-
// only run code path analyzer if the top level node is "Program", skip otherwise
1135-
consteventGenerator=nodeQueue[0].node.type==="Program"
1136-
?newCodePathAnalyzer(newNodeEventGenerator(emitter,{visitorKeys:sourceCode.visitorKeys,fallback:Traverser.getKeys}))
1137-
:newNodeEventGenerator(emitter,{visitorKeys:sourceCode.visitorKeys,fallback:Traverser.getKeys});
1126+
consteventGenerator=newNodeEventGenerator(emitter,{visitorKeys:sourceCode.visitorKeys,fallback:Traverser.getKeys});
11381127

1139-
nodeQueue.forEach(traversalInfo=>{
1140-
currentNode=traversalInfo.node;
1128+
for(conststepofeventQueue){
1129+
switch(step.kind){
1130+
caseSTEP_KIND_VISIT:{
1131+
try{
1132+
if(step.phase===1){
1133+
eventGenerator.enterNode(step.target);
1134+
}else{
1135+
eventGenerator.leaveNode(step.target);
1136+
}
1137+
}catch(err){
1138+
err.currentNode=step.target;
1139+
throwerr;
1140+
}
1141+
break;
1142+
}
11411143

1142-
try{
1143-
if(traversalInfo.isEntering){
1144-
eventGenerator.enterNode(currentNode);
1145-
}else{
1146-
eventGenerator.leaveNode(currentNode);
1144+
caseSTEP_KIND_CALL:{
1145+
emitter.emit(step.target, ...step.args);
1146+
break;
11471147
}
1148-
}catch(err){
1149-
err.currentNode=currentNode;
1150-
throwerr;
1148+
1149+
default:
1150+
thrownewError(`Invalid traversal step found: "${step.type}".`);
11511151
}
1152-
});
1152+
1153+
}
11531154

11541155
returnlintingProblems;
11551156
}

‎lib/rules/constructor-super.js‎

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Original file line numberDiff line numberDiff line change
@@ -119,6 +119,30 @@ function isPossibleConstructor(node) {
119119
}
120120
}
121121

122+
/**
123+
* A class to store information about a code path segment.
124+
*/
125+
classSegmentInfo{
126+
127+
/**
128+
* Indicates if super() is called in all code paths.
129+
*@type {boolean}
130+
*/
131+
calledInEveryPaths=false;
132+
133+
/**
134+
* Indicates if super() is called in any code paths.
135+
*@type {boolean}
136+
*/
137+
calledInSomePaths=false;
138+
139+
/**
140+
* The nodes which have been validated and don't need to be reconsidered.
141+
*@type {ASTNode[]}
142+
*/
143+
validNodes=[];
144+
}
145+
122146
//------------------------------------------------------------------------------
123147
// Rule Definition
124148
//------------------------------------------------------------------------------
@@ -159,12 +183,8 @@ module.exports = {
159183
*/
160184
letfuncInfo=null;
161185

162-
/*
163-
* {Map<string, {calledInSomePaths: boolean, calledInEveryPaths: boolean}>}
164-
* Information for each code path segment.
165-
* - calledInSomePaths: A flag of be called `super()` in some code paths.
166-
* - calledInEveryPaths: A flag of be called `super()` in all code paths.
167-
* - validNodes:
186+
/**
187+
*@type {Record<string, SegmentInfo>}
168188
*/
169189
letsegInfoMap=Object.create(null);
170190

@@ -174,7 +194,16 @@ module.exports = {
174194
*@returns {boolean} The flag which shows `super()` is called in some paths
175195
*/
176196
functionisCalledInSomePath(segment){
177-
returnsegment.reachable&&segInfoMap[segment.id].calledInSomePaths;
197+
returnsegment.reachable&&segInfoMap[segment.id]?.calledInSomePaths;
198+
}
199+
200+
/**
201+
* Determines if a segment has been seen in the traversal.
202+
*@param {CodePathSegment} segment A code path segment to check.
203+
*@returns {boolean} `true` if the segment has been seen.
204+
*/
205+
functionhasSegmentBeenSeen(segment){
206+
return!!segInfoMap[segment.id];
178207
}
179208

180209
/**
@@ -190,10 +219,10 @@ module.exports = {
190219
* If not skipped, this never becomes true after a loop.
191220
*/
192221
if(segment.nextSegments.length===1&&
193-
segment.nextSegments[0].isLoopedPrevSegment(segment)
194-
){
222+
segment.nextSegments[0]?.isLoopedPrevSegment(segment)){
195223
returntrue;
196224
}
225+
197226
returnsegment.reachable&&segInfoMap[segment.id].calledInEveryPaths;
198227
}
199228

@@ -250,9 +279,9 @@ module.exports = {
250279
}
251280

252281
// Reports if `super()` lacked.
253-
constsegments=codePath.returnedSegments;
254-
constcalledInEveryPaths=segments.every(isCalledInEveryPath);
255-
constcalledInSomePaths=segments.some(isCalledInSomePath);
282+
constseenSegments=codePath.returnedSegments.filter(hasSegmentBeenSeen);
283+
constcalledInEveryPaths=seenSegments.every(isCalledInEveryPath);
284+
constcalledInSomePaths=seenSegments.some(isCalledInSomePath);
256285

257286
if(!calledInEveryPaths){
258287
context.report({
@@ -278,18 +307,16 @@ module.exports = {
278307
}
279308

280309
// Initialize info.
281-
constinfo=segInfoMap[segment.id]={
282-
calledInSomePaths:false,
283-
calledInEveryPaths:false,
284-
validNodes:[]
285-
};
310+
constinfo=segInfoMap[segment.id]=newSegmentInfo();
286311

287312
// When there are previous segments, aggregates these.
288313
constprevSegments=segment.prevSegments;
289314

290315
if(prevSegments.length>0){
291-
info.calledInSomePaths=prevSegments.some(isCalledInSomePath);
292-
info.calledInEveryPaths=prevSegments.every(isCalledInEveryPath);
316+
constseenPrevSegments=prevSegments.filter(hasSegmentBeenSeen);
317+
318+
info.calledInSomePaths=seenPrevSegments.some(isCalledInSomePath);
319+
info.calledInEveryPaths=seenPrevSegments.every(isCalledInEveryPath);
293320
}
294321
},
295322

@@ -326,12 +353,12 @@ module.exports = {
326353
funcInfo.codePath.traverseSegments(
327354
{first:toSegment,last:fromSegment},
328355
segment=>{
329-
constinfo=segInfoMap[segment.id];
330-
constprevSegments=segment.prevSegments;
356+
constinfo=segInfoMap[segment.id]??newSegmentInfo();
357+
constseenPrevSegments=segment.prevSegments.filter(hasSegmentBeenSeen);
331358

332359
// Updates flags.
333-
info.calledInSomePaths=prevSegments.some(isCalledInSomePath);
334-
info.calledInEveryPaths=prevSegments.every(isCalledInEveryPath);
360+
info.calledInSomePaths=seenPrevSegments.some(isCalledInSomePath);
361+
info.calledInEveryPaths=seenPrevSegments.every(isCalledInEveryPath);
335362

336363
// If flags become true anew, reports the valid nodes.
337364
if(info.calledInSomePaths||isRealLoop){
@@ -348,6 +375,9 @@ module.exports = {
348375
});
349376
}
350377
}
378+
379+
// save just in case we created a new SegmentInfo object
380+
segInfoMap[segment.id]=info;
351381
}
352382
);
353383
},

‎lib/rules/no-this-before-super.js‎

Lines changed: 28 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -30,6 +30,29 @@ function isConstructorFunction(node) {
3030
);
3131
}
3232

33+
/*
34+
* Information for each code path segment.
35+
* - superCalled: The flag which shows `super()` called in all code paths.
36+
* - invalidNodes: The array of invalid ThisExpression and Super nodes.
37+
*/
38+
/**
39+
*
40+
*/
41+
classSegmentInfo{
42+
43+
/**
44+
* Indicates whether `super()` is called in all code paths.
45+
*@type {boolean}
46+
*/
47+
superCalled=false;
48+
49+
/**
50+
* The array of invalid ThisExpression and Super nodes.
51+
*@type {ASTNode[]}
52+
*/
53+
invalidNodes=[];
54+
}
55+
3356
//------------------------------------------------------------------------------
3457
// Rule Definition
3558
//------------------------------------------------------------------------------
@@ -64,13 +87,7 @@ module.exports = {
6487
*/
6588
letfuncInfo=null;
6689

67-
/*
68-
* Information for each code path segment.
69-
* Each key is the id of a code path segment.
70-
* Each value is an object:
71-
* - superCalled: The flag which shows `super()` called in all code paths.
72-
* - invalidNodes: The array of invalid ThisExpression and Super nodes.
73-
*/
90+
/**@type {Record<string, SegmentInfo>} */
7491
letsegInfoMap=Object.create(null);
7592

7693
/**
@@ -79,7 +96,7 @@ module.exports = {
7996
*@returns {boolean} `true` if `super()` is called.
8097
*/
8198
functionisCalled(segment){
82-
return!segment.reachable||segInfoMap[segment.id].superCalled;
99+
return!segment.reachable||segInfoMap[segment.id]?.superCalled;
83100
}
84101

85102
/**
@@ -285,7 +302,7 @@ module.exports = {
285302
funcInfo.codePath.traverseSegments(
286303
{first:toSegment,last:fromSegment},
287304
(segment,controller)=>{
288-
constinfo=segInfoMap[segment.id];
305+
constinfo=segInfoMap[segment.id]??newSegmentInfo();
289306

290307
if(info.superCalled){
291308
controller.skip();
@@ -295,6 +312,8 @@ module.exports = {
295312
){
296313
info.superCalled=true;
297314
}
315+
316+
segInfoMap[segment.id]=info;
298317
}
299318
);
300319
},

‎lib/rules/no-useless-return.js‎

Lines changed: 7 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -146,7 +146,9 @@ module.exports = {
146146
continue;
147147
}
148148

149-
uselessReturns.push(...segmentInfoMap.get(segment).uselessReturns);
149+
if(segmentInfoMap.has(segment)){
150+
uselessReturns.push(...segmentInfoMap.get(segment).uselessReturns);
151+
}
150152
}
151153

152154
returnuselessReturns;
@@ -182,6 +184,10 @@ module.exports = {
182184

183185
constinfo=segmentInfoMap.get(segment);
184186

187+
if(!info){
188+
return;
189+
}
190+
185191
info.uselessReturns=info.uselessReturns.filter(node=>{
186192
if(scopeInfo.traversedTryBlockStatements&&scopeInfo.traversedTryBlockStatements.length>0){
187193
constreturnInitialRange=node.range[0];
@@ -275,7 +281,6 @@ module.exports = {
275281
* NOTE: This event is notified for only reachable segments.
276282
*/
277283
onCodePathSegmentStart(segment){
278-
279284
scopeInfo.currentSegments.add(segment);
280285

281286
constinfo={

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