typescript-eslint · JoshuaKGoldberg · Feb 5, 2023 · Feb 6, 2023 · Apr 5, 2023 · Apr 5, 2023
diff --git a/.eslintignore.all b/.eslintignore.all
@@ -0,0 +1,17 @@
+node_modules
+dist
+jest.config.js
+fixtures
+coverage
+__snapshots__
+.docusaurus
+build
+
+# Files copied as part of the build
+packages/types/src/generated/**/*.ts
+
+# Playground types downloaded from the web
+packages/website/src/vendor
+
+# Additionally, JS files
+**/*.js
diff --git a/.eslintrc.js b/.eslintrc.js
@@ -41,6 +41,8 @@ module.exports = {
     allowAutomaticSingleRunInference: true,
     tsconfigRootDir: __dirname,
     warnOnUnsupportedTypeScriptVersion: false,
+    EXPERIMENTAL_memoizeTypeCheckingAPIs:
+      !!process.env.MEMOIZE_TYPE_CHECKING_APIS,
     EXPERIMENTAL_useSourceOfProjectReferenceRedirect: false,
     cacheLifetime: {
       // we pretty well never create/change tsconfig structure - so need to ever evict the cache

diff --git a/.eslintrc.many.js b/.eslintrc.many.js
@@ -0,0 +1,22 @@
+// A version of our config that enables many more rules, for use in perf testing
+
+// @ts-check
+/** @type {import('./packages/utils/src/ts-eslint/Linter.js').Linter.Config} */
+module.exports = {
+  extends: ['plugin:@typescript-eslint/all', 'prettier'],
+  overrides: [
+    {
+      files: ['*.js'],
+      extends: ['plugin:@typescript-eslint/disable-type-checked'],
+    },
+  ],
+  parser: '@typescript-eslint/parser',
+  parserOptions: {
+    EXPERIMENTAL_memoizeTypeCheckingAPIs:
+      !!process.env.MEMOIZE_TYPE_CHECKING_APIS,
+    project: ['./tsconfig.eslint.json'],
+    tsconfigRootDir: __dirname,
+  },
+  plugins: ['@typescript-eslint'],
+  root: true,
+};
diff --git a/docs/architecture/TypeScript-ESTree.mdx b/docs/architecture/TypeScript-ESTree.mdx
@@ -147,6 +147,13 @@ interface ParseAndGenerateServicesOptions extends ParseOptions {
    */
   errorOnTypeScriptSyntacticAndSemanticIssues?: boolean;
 
+  /**
+   * ***EXPERIMENTAL FLAG*** - Use this at your own risk.
+   *
+   * Whether to memoize many of TypeScript's type checking APIs.
+   */
+  EXPERIMENTAL__memoizeTypeCheckingAPIs?: boolean;
+
   /**
    * ***EXPERIMENTAL FLAG*** - Use this at your own risk.
    *

diff --git a/package.json b/package.json
@@ -38,6 +38,7 @@
     "generate-website-dts": "nx run website:generate-website-dts",
     "generate-lib": "nx run scope-manager:generate-lib",
     "lint-fix": "yarn lint --fix",
+    "lint-many": "npx eslint --config .eslintrc.many.js --ignore-path .eslintignore.all packages/",
     "lint-markdown-fix": "yarn lint-markdown --fix",
     "lint-markdown": "markdownlint \"**/*.md\" --config=.markdownlint.json --ignore-path=.markdownlintignore",
     "lint": "nx run-many --target=lint --parallel",
@@ -82,8 +83,9 @@
     "cross-fetch": "^3.1.5",
     "cspell": "^6.0.0",
     "downlevel-dts": ">=0.11.0",
-    "eslint-plugin-deprecation": "^1.3.3",
     "eslint": "^8.34.0",
+    "eslint-config-prettier": "^8.8.0",
+    "eslint-plugin-deprecation": "^1.3.3",
     "eslint-plugin-eslint-comments": "^3.2.0",
     "eslint-plugin-eslint-plugin": "^5.0.8",
     "eslint-plugin-import": "^2.27.5",

diff --git a/packages/types/src/parser-options.ts b/packages/types/src/parser-options.ts
@@ -47,6 +47,7 @@ interface ParserOptions {
   debugLevel?: DebugLevel;
   errorOnTypeScriptSyntacticAndSemanticIssues?: boolean;
   errorOnUnknownASTType?: boolean;
+  EXPERIMENTAL_memoizeTypeCheckingAPIs?: boolean;
   EXPERIMENTAL_useSourceOfProjectReferenceRedirect?: boolean; // purposely undocumented for now
   extraFileExtensions?: string[];
   filePath?: string;

diff --git a/packages/typescript-estree/src/createParserServices.ts b/packages/typescript-estree/src/createParserServices.ts
@@ -3,9 +3,40 @@ import type * as ts from 'typescript';
 import type { ASTMaps } from './convert';
 import type { ParserServices } from './parser-options';
 
+type MethodKeyOf<Container> = keyof {
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  [Key in keyof Container]: Container[Key] extends (parameter: any) => unknown
+    ? Key
+    : never;
+};
+
+function memoizeMethods<Container, Keys extends MethodKeyOf<Container>[]>(
+  container: Container,
+  keys: Keys,
+): void {
+  for (const key of keys) {
+    const originalMethod = (
+      container[key] as (parameter: object) => unknown
+    ).bind(container);
+    const cache = new WeakMap<object, unknown>();
+
+    container[key] = ((parameter: object): unknown => {
+      const cached = cache.get(parameter);
+      if (cached) {
+        return cached;
+      }
+
+      const created = originalMethod(parameter);
+      cache.set(parameter, created);
+      return created;
+    }) as Container[typeof key];
+  }
+}
+
 export function createParserServices(
   astMaps: ASTMaps,
   program: ts.Program | null,
+  memoize: boolean,
 ): ParserServices {
   if (!program) {
     // we always return the node maps because
@@ -16,6 +47,10 @@ export function createParserServices(
 
   const checker = program.getTypeChecker();
 
+  if (memoize) {
+    memoizeMethods(checker, ['getSymbolAtLocation', 'getTypeAtLocation']);
+  }
+
   return {
     program,
     ...astMaps,

diff --git a/packages/typescript-estree/src/parseSettings/createParseSettings.ts b/packages/typescript-estree/src/parseSettings/createParseSettings.ts
@@ -47,6 +47,8 @@ export function createParseSettings(
         : new Set(),
     errorOnTypeScriptSyntacticAndSemanticIssues: false,
     errorOnUnknownASTType: options.errorOnUnknownASTType === true,
+    EXPERIMENTAL_memoizeTypeCheckingAPIs:
+      options.EXPERIMENTAL_memoizeTypeCheckingAPIs === true,
     EXPERIMENTAL_useSourceOfProjectReferenceRedirect:
       options.EXPERIMENTAL_useSourceOfProjectReferenceRedirect === true,
     extraFileExtensions:

diff --git a/packages/typescript-estree/src/parseSettings/index.ts b/packages/typescript-estree/src/parseSettings/index.ts
@@ -57,6 +57,11 @@ export interface MutableParseSettings {
    */
   errorOnUnknownASTType: boolean;
 
+  /**
+   * Whether to memoize many of TypeScript's type checking APIs.
+   */
+  EXPERIMENTAL_memoizeTypeCheckingAPIs: boolean;
+
   /**
    * Whether TS should use the source files for referenced projects instead of the compiled .d.ts files.
    *

diff --git a/packages/typescript-estree/src/parser-options.ts b/packages/typescript-estree/src/parser-options.ts
@@ -94,6 +94,13 @@ interface ParseAndGenerateServicesOptions extends ParseOptions {
    */
   errorOnTypeScriptSyntacticAndSemanticIssues?: boolean;
 
+  /**
+   * ***EXPERIMENTAL FLAG*** - Use this at your own risk.
+   *
+   * Whether to memoize many of TypeScript's type checking APIs.
+   */
+  EXPERIMENTAL_memoizeTypeCheckingAPIs?: boolean;
+
   /**
    * ***EXPERIMENTAL FLAG*** - Use this at your own risk.
    *

diff --git a/packages/typescript-estree/src/parser.ts b/packages/typescript-estree/src/parser.ts
@@ -270,7 +270,11 @@ function parseAndGenerateServices<T extends TSESTreeOptions = TSESTreeOptions>(
    */
   return {
     ast: estree as AST<T>,
-    services: createParserServices(astMaps, program),
+    services: createParserServices(
+      astMaps,
+      program,
+      parseSettings.EXPERIMENTAL_memoizeTypeCheckingAPIs,
+    ),
   };
 }
 

diff --git a/packages/website/src/components/linter/config.ts b/packages/website/src/components/linter/config.ts
@@ -13,6 +13,7 @@ export const parseSettings: ParseSettings = {
   DEPRECATED__createDefaultProgram: false,
   errorOnTypeScriptSyntacticAndSemanticIssues: false,
   errorOnUnknownASTType: false,
+  EXPERIMENTAL_memoizeTypeCheckingAPIs: false,
   EXPERIMENTAL_useSourceOfProjectReferenceRedirect: false,
   extraFileExtensions: [],
   filePath: '',

diff --git a/yarn.lock b/yarn.lock
@@ -6855,6 +6855,11 @@ escape-string-regexp@^4.0.0:
   resolved "https://registry.yarnpkg.com/escape-string-regexp/-/escape-string-regexp-4.0.0.tgz#14ba83a5d373e3d311e5afca29cf5bfad965bf34"
   integrity sha512-TtpcNJ3XAzx3Gq8sWRzJaVajRs0uVxA2YAkdb1jm2YkPz4G6egUFAyA3n5vtEIZefPk5Wa4UXbKuS5fKkJWdgA==
 
+eslint-config-prettier@^8.8.0:
+  version "8.8.0"
+  resolved "https://registry.yarnpkg.com/eslint-config-prettier/-/eslint-config-prettier-8.8.0.tgz#bfda738d412adc917fd7b038857110efe98c9348"
+  integrity sha512-wLbQiFre3tdGgpDv67NQKnJuTlcUVYHas3k+DZCc2U2BadthoEY4B7hLPvAxaqdyOGCzuLfii2fqGph10va7oA==
+
 eslint-import-resolver-node@^0.3.7:
   version "0.3.7"
   resolved "https://registry.yarnpkg.com/eslint-import-resolver-node/-/eslint-import-resolver-node-0.3.7.tgz#83b375187d412324a1963d84fa664377a23eb4d7"