perf: Use `Map` instead of `AstMetadataApiWithTargetsResolver[]` for faster matching by igeligel · Pull Request #679 · amilajack/eslint-plugin-compat

igeligel · 2026-02-15T15:24:30Z

This refactors the getRulesForTargets function to return Map<string, AstMetadataApiWithTargetsResolver> for each expression matching.

Before it returned:

{
  CallExpression: AstMetadataApiWithTargetsResolver[];
  NewExpression: AstMetadataApiWithTargetsResolver[];
  MemberExpression: AstMetadataApiWithTargetsResolver[];
  ExpressionStatement: AstMetadataApiWithTargetsResolver[];
  Literal: AstMetadataApiWithTargetsResolver[];
}

Now it returns:

{
  callExpression: RuleMap;
  newExpression: RuleMap;
  expressionStatement: RuleMap;
  memberExpression: RuleMap;
  literal: RuleMap;
};

This also requires changes now in helpers.tsx and makes a lot of rules.find( calls much faster. O(1) instead of O(n).

I benchmarked the changes as well (Thanks for providing the benchmarks):

Before: https://gist.github.com/igeligel/8c2dd38d1da1363f3a57c3820b208688#file-1-before-txt
After: https://gist.github.com/igeligel/8c2dd38d1da1363f3a57c3820b208688#file-2-after-txt

Repo	Before mean (s)	After mean (s)	Change
bootstrap	0.609	0.335	~45% faster
jquery	1.089	0.741	~32% faster
handlebars.js	0.462	0.376	~19% faster
aframe	8.070	6.280	~22% faster
pixi.js	2.284	1.743	~24% faster
create-react-app	2.685	2.202	~18% faster
electron-react-boilerplate	0.0316	0.0271	~14% faster
preact	0.00689	0.00528	~23% faster

There are some more improvements as well that I will follow up in other Pull Requests.

joshkel · 2026-02-18T21:55:06Z

If I'm following this correctly, this looks like it serves the same purpose as my work at #615, and it looks simpler too. I'll close #615 if this is merged.

Use Maps instead of arrays

igeligel · 2026-02-21T21:08:36Z

So updated the branch. Updated benchmarks: https://gist.github.com/igeligel/548048b85386d1f3760ba80e5be0f628

…ith-map

igeligel · 2026-04-17T11:42:09Z

Fixed conflicts by merging the main function.

New benchmark results: https://gist.github.com/igeligel/fabb1ddfdeefcf66c777788eb875845f

cc @amilajack

amilajack · 2026-04-18T00:10:07Z

@codex review

chatgpt-codex-connector · 2026-04-18T00:10:17Z

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.

kevinpeters-stripe · 2026-04-27T08:45:40Z

Hey @amilajack ,
Mind having a look at this again please?

amilajack · 2026-04-27T14:37:26Z

@codex review

Copilot

Pull request overview

This PR refactors rule selection and lookup in the compat ESLint rule to speed up matching by replacing per-node linear searches over arrays with Map-based lookups.

Changes:

Refactor getRulesForTargets to build and return per-AST-node-type Map structures for faster rule retrieval.
Update helper lint functions (lintCallExpression, lintNewExpression, etc.) to consume Map inputs instead of arrays and use .get() lookups.
Rewire compat rule wiring to pass the new maps into the lint helpers.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
src/rules/compat.ts	Builds per-node-type rule maps in `getRulesForTargets` and updates rule visitor bindings to pass maps.
src/helpers.ts	Changes lint helper APIs to accept rule maps and perform `Map` lookups during AST traversal.

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

+    const callExpression = new Map<string, AstMetadataApiWithTargetsResolver>();
+    for (const rule of byType.CallExpression) {
+      const key = rule.object.toLowerCase();
+      if (!callExpression.has(key)) callExpression.set(key, rule);
+    }


+      const protoChainKey = rule.protoChainId.toLowerCase();
+      if (!memberExpression.has(protoChainKey))
+        memberExpression.set(protoChainKey, rule);
+      const key = (rule.property ? `${rule.object}.${rule.property}` : rule.object).toLowerCase();


  if (!node.callee) return;
  const calleeName = node.callee.name;
-  const failingRule = rules.find((rule) => rule.object === calleeName);
+  if (!calleeName) return;
+  const failingRule = rulesMap.get(calleeName.toLowerCase());
  if (failingRule)


-    const failingRule = rules.find(
-      (rule) => rule.protoChainId === protoChainId
-    );
+    const failingRule = rulesMap.get(protoChainId.toLowerCase());


 const getRulesForTargets = memoize(
-  (targetsJSON: string, lintAllEsApis: boolean): RulesFilteredByTargets => {
-    const result = {
+  (targetsJSON: string, lintAllEsApis: boolean): RuleMapsForTargets => {


chatgpt-codex-connector

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 16e3367912

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

Open a pull request for review
Mark a draft as ready
Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".

chatgpt-codex-connector · 2026-04-27T14:43:20Z

  const calleeName = node.callee.name;
-  const failingRule = rules.find((rule) => rule.object === calleeName);
+  if (!calleeName) return;
+  const failingRule = rulesMap.get(calleeName.toLowerCase());


Restore case-sensitive matching for call/new/expression

Lowercasing identifiers during lookup changes CallExpression/NewExpression/ExpressionStatement matching from exact to case-insensitive, which introduces false positives for non-equivalent symbols (for example new url() now matches the URL rule). Previous logic only allowed case-insensitive matching in the browser-global member-expression path; this broad lookup makes unrelated identifiers fail compat checks purely because they share lowercase forms.

Useful? React with 👍 / 👎.

chatgpt-codex-connector · 2026-04-27T14:43:20Z

+      rulesMap.get(`${objectName}.${propertyName}`.toLowerCase()) ??
+      rulesMap.get(objectName.toLowerCase());


Preserve property-case checks in member lookup

The member-expression key is lowercased as ${objectName}.${propertyName}, so property matching becomes case-insensitive even for non-browser globals. Because the subsequent guard only validates failingRule.object case, Promise.Resolve will match Promise.resolve and be reported as unsupported. This regresses correctness by flagging APIs that are not actually referenced.

Useful? React with 👍 / 👎.

igeligel · 2026-04-27T15:02:32Z

Thanks for the review! Will adjust based on the comments later.

amilajack · 2026-04-27T15:44:15Z

feel free to only focus on the codex comments

Feedback

igeligel · 2026-04-27T19:47:32Z

@amilajack - Adjusted and I have added some tests as well: https://github.com/amilajack/eslint-plugin-compat/pull/679/changes#diff-3b214fee0799850287be9de60a3b777c8d9c2d8128458b0e465bbe197dbe794e

…faster matching (#679) * perf: compat Use Maps instead of arrays * refactor: ci Feedback

…faster matching (#679)

## [7.0.2](v7.0.1...v7.0.2) (2026-04-29) ### Performance Improvements * Use `Map` instead of `AstMetadataApiWithTargetsResolver[]` for faster matching ([#679](#679)) ([fecdcc6](fecdcc6))

perf: compat

ca74d10

Use Maps instead of arrays

igeligel force-pushed the performance-improvement-replace-rules-find-with-map branch from 3d3032d to ca74d10 Compare February 20, 2026 12:07

Merge branch 'main' into performance-improvement-replace-rules-find-w…

16e3367

…ith-map

amilajack requested a review from Copilot April 27, 2026 14:36

Copilot started reviewing on behalf of amilajack April 27, 2026 14:37 View session

Copilot AI reviewed Apr 27, 2026

View reviewed changes

chatgpt-codex-connector Bot reviewed Apr 27, 2026

View reviewed changes

refactor: ci

89db30c

Feedback

amilajack merged commit c101643 into amilajack:main Apr 27, 2026
5 checks passed

amilajack pushed a commit that referenced this pull request Apr 29, 2026

perf: Use Map instead of AstMetadataApiWithTargetsResolver[] for …

517b95d

…faster matching (#679) * perf: compat Use Maps instead of arrays * refactor: ci Feedback

amilajack pushed a commit that referenced this pull request Apr 29, 2026

perf: Use Map instead of AstMetadataApiWithTargetsResolver[] for …

fecdcc6

…faster matching (#679)

		rulesMap.get(`${objectName}.${propertyName}`.toLowerCase()) ??
		rulesMap.get(objectName.toLowerCase());

Uh oh!

Conversation

igeligel commented Feb 15, 2026

Uh oh!

joshkel commented Feb 18, 2026

Uh oh!

igeligel commented Feb 21, 2026

Uh oh!

igeligel commented Apr 17, 2026

Uh oh!

amilajack commented Apr 18, 2026

Uh oh!

chatgpt-codex-connector Bot commented Apr 18, 2026

Uh oh!

kevinpeters-stripe commented Apr 27, 2026

Uh oh!

amilajack commented Apr 27, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

chatgpt-codex-connector Bot left a comment

Choose a reason for hiding this comment

💡 Codex Review

Uh oh!

chatgpt-codex-connector Bot Apr 27, 2026

Choose a reason for hiding this comment

Uh oh!

chatgpt-codex-connector Bot Apr 27, 2026

Choose a reason for hiding this comment

Uh oh!

igeligel commented Apr 27, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

amilajack commented Apr 27, 2026

Uh oh!

igeligel commented Apr 27, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

igeligel commented Apr 27, 2026 •

edited

Loading