From c3d1ae901906cb680616268cc297304521e76a3c Mon Sep 17 00:00:00 2001
From: overlookmotel <557937+overlookmotel@users.noreply.github.com>
Date: Wed, 28 Jan 2026 23:02:39 +0000
Subject: [PATCH] test(linter/plugins): conformance tester identify known
 parsers by `parseForESLint` function (#18680)

Conformance tester was identifying known parsers specified by test cases by comparing the `parser` object to known values. Instead, compare `parser.parseForESLint` functions.

This produces an accurate match even when the test case object is deep cloned which results in the `parser` object being a new (unknown) object. But the `parseForESLint` function stays the same after cloning.

`eslint-plugin-sonarjs` does this kind of deep cloning.
---
 apps/oxlint/conformance/src/index.ts       | 12 +++++++-----
 apps/oxlint/conformance/src/rule_tester.ts | 12 ++++++------
 2 files changed, 13 insertions(+), 11 deletions(-)

diff --git a/apps/oxlint/conformance/src/index.ts b/apps/oxlint/conformance/src/index.ts
index 5f7b7274874eb..0de2670cbbe6b 100644
--- a/apps/oxlint/conformance/src/index.ts
+++ b/apps/oxlint/conformance/src/index.ts
@@ -31,7 +31,7 @@ import { TEST_GROUPS } from "./groups/index.ts";
 import { setCurrentGroup, setCurrentRule, resetCurrentRule } from "./capture.ts";
 import { SHOULD_SKIP_GROUP, SHOULD_SKIP_RULE } from "./filter.ts";
 import { generateReport } from "./report.ts";
-import { RuleTester, parserModules, parserModulePaths } from "./rule_tester.ts";
+import { RuleTester, parseForESLintFns, parserPaths } from "./rule_tester.ts";
 
 import type { RuleResult } from "./capture.ts";
 import type { Language, TestCase } from "./rule_tester.ts";
@@ -254,8 +254,8 @@ function runGroup(group: TestGroup, mocks: Mocks) {
   // Get custom parsers
   console.log(`Loading custom parsers for ${groupName}...`);
 
-  parserModules.clear();
-  parserModulePaths.clear();
+  parseForESLintFns.clear();
+  parserPaths.clear();
 
   for (const parserDetails of group.parsers) {
     const path = resolveFromTestsDir(parserDetails.specifier);
@@ -264,8 +264,10 @@ function runGroup(group: TestGroup, mocks: Mocks) {
     // Set `default` export on parser module to work around apparent bug in `tsx`
     if (parser && parser.default === undefined) parser.default = parser;
 
-    parserModules.set(parser, parserDetails);
-    parserModulePaths.set(path, parserDetails);
+    if (typeof parser.parseForESLint === "function") {
+      parseForESLintFns.set(parser.parseForESLint, parserDetails);
+    }
+    parserPaths.set(path, parserDetails);
   }
 
   // Find test files and run tests
diff --git a/apps/oxlint/conformance/src/rule_tester.ts b/apps/oxlint/conformance/src/rule_tester.ts
index 1777d35108616..a55c9debd4b24 100644
--- a/apps/oxlint/conformance/src/rule_tester.ts
+++ b/apps/oxlint/conformance/src/rule_tester.ts
@@ -34,9 +34,9 @@ export type ValidTestCase = RuleTester.ValidTestCase & TestCaseExtension;
 export type InvalidTestCase = RuleTester.InvalidTestCase & TestCaseExtension;
 export type TestCase = ValidTestCase | InvalidTestCase;
 
-// Maps of parser modules and parser paths to parser details (language + specifier)
-export const parserModules: Map<unknown, ParserDetails> = new Map();
-export const parserModulePaths: Map<string, ParserDetails> = new Map();
+// Maps of parser `parseForESLint` functions and parser paths to parser details (language + specifier)
+export const parseForESLintFns: Map<Function, ParserDetails> = new Map();
+export const parserPaths: Map<string, ParserDetails> = new Map();
 
 // Set up `RuleTester` to use our hooks
 RuleTester.describe = describe;
@@ -174,8 +174,8 @@ function modifyTestCase(test: TestCase): void {
   // - Old ESLint versions: `test.parser` (absolute path to parser)
   let parserDetails: ParserDetails | null = null;
 
-  if (languageOptions.parser != null) {
-    parserDetails = parserModules.get(languageOptions.parser) ?? null;
+  if (languageOptions.parser?.parseForESLint != null) {
+    parserDetails = parseForESLintFns.get(languageOptions.parser.parseForESLint) ?? null;
     if (parserDetails !== null) delete languageOptions.parser;
   }
 
@@ -183,7 +183,7 @@ function modifyTestCase(test: TestCase): void {
     if (parserDetails !== null) {
       throw new Error("Both `test.parser` and `test.languageOptions.parser` specified");
     }
-    parserDetails = parserModulePaths.get(test.parser) ?? null;
+    parserDetails = parserPaths.get(test.parser) ?? null;
     if (parserDetails === null) {
       // Set `languageOptions.parser` so an error is thrown.
       // Store in stored test case so appears in snapshot.