typescript-eslint · JoshuaKGoldberg · Feb 10, 2023 · Nov 25, 2022 · Nov 25, 2022 · Nov 25, 2022
diff --git a/docs/architecture/Parser.mdx b/docs/architecture/Parser.mdx
@@ -45,7 +45,7 @@ interface ParserOptions {
   lib?: string[];
   moduleResolver?: string;
   program?: import('typescript').Program;
-  project?: string | string[];
+  project?: string | string[] | true;
   projectFolderIgnoreList?: string[];
   tsconfigRootDir?: string;
   warnOnUnsupportedTypeScriptVersion?: boolean;
@@ -188,6 +188,9 @@ This option allows you to provide a path to your project's `tsconfig.json`. **Th
 - Accepted values:
 
   ```js
+  // find the tsconfig.json nearest each source file
+  project: true,
+
   // path
   project: './tsconfig.json';
 
@@ -198,6 +201,10 @@ This option allows you to provide a path to your project's `tsconfig.json`. **Th
   project: ['./packages/**/tsconfig.json', './separate-package/tsconfig.json'];
   ```
 
+- If `true`, each source file's parse will find the nearest `tsconfig.json` file to that source file.
+
+  - This is done by checking that source file's directory tree for the nearest `tsconfig.json`.
+
 - If you use project references, TypeScript will not automatically use project references to resolve files. This means that you will have to add each referenced tsconfig to the `project` field either separately, or via a glob.
 
 - Note that using wide globs `**` in your `parserOptions.project` may cause performance implications. Instead of globs that use `**` to recursively check all folders, prefer paths that use a single `*` at a time. For more info see [#2611](https://github.com/typescript-eslint/typescript-eslint/issues/2611).

diff --git a/docs/architecture/TypeScript-ESTree.mdx b/docs/architecture/TypeScript-ESTree.mdx
@@ -174,10 +174,11 @@ interface ParseAndGenerateServicesOptions extends ParseOptions {
   preserveNodeMaps?: boolean;
 
   /**
-   * Absolute (or relative to `tsconfigRootDir`) paths to the tsconfig(s).
+   * Absolute (or relative to `tsconfigRootDir`) paths to the tsconfig(s),
+   * or `true` to find the nearest tsconfig.json to the file.
    * If this is provided, type information will be returned.
    */
-  project?: string | string[];
+  project?: string | string[] | true;
 
   /**
    * If you provide a glob (or globs) to the project option, you can use this option to ignore certain folders from

diff --git a/docs/linting/Typed_Linting.mdx b/docs/linting/Typed_Linting.mdx
@@ -18,7 +18,7 @@ module.exports = {
   parser: '@typescript-eslint/parser',
   // Added lines start
   parserOptions: {
-    project: ['./tsconfig.json'],
+    project: true,
     tsconfigRootDir: __dirname,
   },
   // Added lines end
@@ -36,6 +36,31 @@ In more detail:
 With that done, run the same lint command you ran before.
 You may see new rules reporting errors based on type information!
 
+## Specifying TSConfigs
+
+The `parserOptions.project` option can be turned on with either:
+
+- `true`: to always use `tsconfig.json`s nearest to source files
+- `string | string[]`: any number of glob paths to match TSConfig files relative to the
+
+For example, if you use a specific `tsconfig.eslint.json` for linting, you'd specify:
+
+```js title=".eslintrc.js"
+module.exports = {
+  // ...
+  parserOptions: {
+    project: './tsconfig.eslint.json',
+  },
+  // ...
+};
+```
+
+See [the `@typescript-eslint/parser` docs for more details](https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/parser/README.md#parseroptionsproject).
+
+:::note
+If your project is a multi-package monorepo, see [our docs on configuring a monorepo](./typed-linting/Monorepos.mdx).
+:::
+
 ## FAQs
 
 ### How is performance?

diff --git a/docs/linting/typed-linting/Monorepos.mdx b/docs/linting/typed-linting/Monorepos.mdx
@@ -53,7 +53,7 @@ module.exports = {
   parserOptions: {
     tsconfigRootDir: __dirname,
     // Remove this line
-    project: ['./tsconfig.json'],
+    project: true,
     // Add this line
     project: ['./tsconfig.eslint.json', './packages/*/tsconfig.json'],
   },

diff --git a/packages/types/src/parser-options.ts b/packages/types/src/parser-options.ts
@@ -52,7 +52,7 @@ interface ParserOptions {
   filePath?: string;
   loc?: boolean;
   program?: Program;
-  project?: string | string[];
+  project?: string | string[] | true;
   projectFolderIgnoreList?: (string | RegExp)[];
   range?: boolean;
   sourceType?: SourceType;

diff --git a/packages/typescript-estree/src/parseSettings/ExpiringCache.ts b/packages/typescript-estree/src/parseSettings/ExpiringCache.ts
@@ -3,15 +3,18 @@ import type { CacheDurationSeconds } from '@typescript-eslint/types';
 export const DEFAULT_TSCONFIG_CACHE_DURATION_SECONDS = 30;
 const ZERO_HR_TIME: [number, number] = [0, 0];
 
+export interface CacheLike<Key, Value> {
+  get(key: Key): Value | void;
+  set(key: Key, value: Value): this;
+}
+
 /**
  * A map with key-level expiration.
  */
-export class ExpiringCache<TKey, TValue> {
+export class ExpiringCache<TKey, TValue> implements CacheLike<TKey, TValue> {
   readonly #cacheDurationSeconds: CacheDurationSeconds;
-  /**
-   * The mapping of path-like string to the resolved TSConfig(s)
-   */
-  protected readonly map = new Map<
+
+  readonly #map = new Map<
     TKey,
     Readonly<{
       value: TValue;
@@ -24,7 +27,7 @@ export class ExpiringCache<TKey, TValue> {
   }
 
   set(key: TKey, value: TValue): this {
-    this.map.set(key, {
+    this.#map.set(key, {
       value,
       lastSeen:
         this.#cacheDurationSeconds === 'Infinity'
@@ -36,7 +39,7 @@ export class ExpiringCache<TKey, TValue> {
   }
 
   get(key: TKey): TValue | undefined {
-    const entry = this.map.get(key);
+    const entry = this.#map.get(key);
     if (entry?.value != null) {
       if (this.#cacheDurationSeconds === 'Infinity') {
         return entry.value;
@@ -48,22 +51,14 @@ export class ExpiringCache<TKey, TValue> {
         return entry.value;
       } else {
         // key has expired - clean it up to free up memory
-        this.cleanupKey(key);
+        this.#map.delete(key);
       }
     }
     // no hit :'(
     return undefined;
   }
 
-  protected cleanupKey(key: TKey): void {
-    this.map.delete(key);
-  }
-
-  get size(): number {
-    return this.map.size;
-  }
-
   clear(): void {
-    this.map.clear();
+    this.#map.clear();
   }
 }
diff --git a/packages/typescript-estree/src/parseSettings/createParseSettings.ts b/packages/typescript-estree/src/parseSettings/createParseSettings.ts
@@ -2,6 +2,11 @@ import debug from 'debug';
 
 import { ensureAbsolutePath } from '../create-program/shared';
 import type { TSESTreeOptions } from '../parser-options';
+import {
+  DEFAULT_TSCONFIG_CACHE_DURATION_SECONDS,
+  ExpiringCache,
+} from './ExpiringCache';
+import { getProjectConfigFiles } from './getProjectConfigFiles';
 import type { MutableParseSettings } from './index';
 import { inferSingleRun } from './inferSingleRun';
 import { resolveProjectList } from './resolveProjectList';
@@ -11,10 +16,13 @@ const log = debug(
   'typescript-eslint:typescript-estree:parser:parseSettings:createParseSettings',
 );
 
+let TSCONFIG_MATCH_CACHE: ExpiringCache<string, string> | null;
+
 export function createParseSettings(
   code: string,
   options: Partial<TSESTreeOptions> = {},
 ): MutableParseSettings {
+  const singleRun = inferSingleRun(options);
   const tsconfigRootDir =
     typeof options.tsconfigRootDir === 'string'
       ? options.tsconfigRootDir
@@ -58,8 +66,14 @@ export function createParseSettings(
     programs: Array.isArray(options.programs) ? options.programs : null,
     projects: [],
     range: options.range === true,
-    singleRun: inferSingleRun(options),
+    singleRun,
     tokens: options.tokens === true ? [] : null,
+    tsconfigMatchCache: (TSCONFIG_MATCH_CACHE ??= new ExpiringCache(
+      singleRun
+        ? 'Infinity'
+        : options.cacheLifetime?.glob ??
+          DEFAULT_TSCONFIG_CACHE_DURATION_SECONDS,
+    )),
     tsconfigRootDir,
   };
 
@@ -95,7 +109,7 @@ export function createParseSettings(
   if (!parseSettings.programs) {
     parseSettings.projects = resolveProjectList({
       cacheLifetime: options.cacheLifetime,
-      project: options.project,
+      project: getProjectConfigFiles(parseSettings, options.project),
       projectFolderIgnoreList: options.projectFolderIgnoreList,
       singleRun: parseSettings.singleRun,
       tsconfigRootDir: tsconfigRootDir,

diff --git a/packages/typescript-estree/src/parseSettings/getProjectConfigFiles.ts b/packages/typescript-estree/src/parseSettings/getProjectConfigFiles.ts
@@ -0,0 +1,59 @@
+import debug from 'debug';
+import * as fs from 'fs';
+import * as path from 'path';
+
+import type { ParseSettings } from '.';
+
+const log = debug('typescript-eslint:typescript-estree:getProjectConfigFiles');
+
+/**
+ * Checks for a matching TSConfig to a file including its parent directories,
+ * permanently caching results under each directory it checks.
+ *
+ * @remarks
+ * We don't (yet!) have a way to attach file watchers on disk, but still need to
+ * cache file checks for rapid subsequent calls to fs.existsSync. See discussion
+ * in https://github.com/typescript-eslint/typescript-eslint/issues/101.
+ */
+export function getProjectConfigFiles(
+  parseSettings: Pick<
+    ParseSettings,
+    'filePath' | 'tsconfigMatchCache' | 'tsconfigRootDir'
+  >,
+  project: string | string[] | true | undefined,
+): string[] | undefined {
+  if (project !== true) {
+    return project === undefined || Array.isArray(project)
+      ? project
+      : [project];
+  }
+
+  log('Looking for tsconfig.json at or above file: %s', parseSettings.filePath);
+  let directory = path.dirname(parseSettings.filePath);
+  const checkedDirectories = [directory];
+
+  do {
+    log('Checking tsconfig.json path: %s', directory);
+    const tsconfigPath = path.join(directory, 'tsconfig.json');
+    const cached =
+      parseSettings.tsconfigMatchCache.get(directory) ??
+      (fs.existsSync(tsconfigPath) && tsconfigPath);
+
+    if (cached) {
+      for (const directory of checkedDirectories) {
+        parseSettings.tsconfigMatchCache.set(directory, cached);
+      }
+      return [cached];
+    }
+
+    directory = path.dirname(directory);
+    checkedDirectories.push(directory);
+  } while (
+    directory.length > 1 &&
+    directory.length >= parseSettings.tsconfigRootDir.length
+  );
+
+  throw new Error(
+    `project was set to \`true\` but couldn't find any tsconfig.json relative to '${parseSettings.filePath}' within '${parseSettings.tsconfigRootDir}'.`,
+  );
+}
diff --git a/packages/typescript-estree/src/parseSettings/index.ts b/packages/typescript-estree/src/parseSettings/index.ts
@@ -2,6 +2,7 @@ import type * as ts from 'typescript';
 
 import type { CanonicalPath } from '../create-program/shared';
 import type { TSESTree } from '../ts-estree';
+import type { CacheLike } from './ExpiringCache';
 
 type DebugModule = 'typescript-eslint' | 'eslint' | 'typescript';
 
@@ -115,6 +116,11 @@ export interface MutableParseSettings {
    */
   tokens: null | TSESTree.Token[];
 
+  /**
+   * Caches searches for TSConfigs from project directories.
+   */
+  tsconfigMatchCache: CacheLike<string, string>;
+
   /**
    * The absolute path to the root directory for all provided `project`s.
    */

diff --git a/packages/typescript-estree/src/parser-options.ts b/packages/typescript-estree/src/parser-options.ts
@@ -120,10 +120,11 @@ interface ParseAndGenerateServicesOptions extends ParseOptions {
   preserveNodeMaps?: boolean;
 
   /**
-   * Absolute (or relative to `tsconfigRootDir`) paths to the tsconfig(s).
+   * Absolute (or relative to `tsconfigRootDir`) paths to the tsconfig(s),
+   * or `true` to find the nearest tsconfig.json to the file.
    * If this is provided, type information will be returned.
    */
-  project?: string | string[];
+  project?: string | string[] | true;
 
   /**
    * If you provide a glob (or globs) to the project option, you can use this option to ignore certain folders from

diff --git a/packages/typescript-estree/tests/fixtures/projectTrue/nested/deep/included.ts b/packages/typescript-estree/tests/fixtures/projectTrue/nested/deep/included.ts
@@ -0,0 +1 @@
+const b = true;
diff --git a/packages/typescript-estree/tests/fixtures/projectTrue/nested/included.ts b/packages/typescript-estree/tests/fixtures/projectTrue/nested/included.ts
@@ -0,0 +1 @@
+const b = true;
diff --git a/packages/typescript-estree/tests/fixtures/projectTrue/nested/tsconfig.json b/packages/typescript-estree/tests/fixtures/projectTrue/nested/tsconfig.json
@@ -0,0 +1,3 @@
+{
+  "include": ["."]
+}
diff --git a/packages/typescript-estree/tests/fixtures/projectTrue/notIncluded.ts b/packages/typescript-estree/tests/fixtures/projectTrue/notIncluded.ts
@@ -0,0 +1 @@
+const c = true;
diff --git a/packages/typescript-estree/tests/lib/createParseSettings.test.ts b/packages/typescript-estree/tests/lib/createParseSettings.test.ts
@@ -0,0 +1,14 @@
+import { createParseSettings } from '../../src/parseSettings/createParseSettings';
+
+describe('createParseSettings', () => {
+  describe('tsconfigMatchCache', () => {
+    it('reuses the TSConfig match cache when called a subsequent time', () => {
+      const parseSettings1 = createParseSettings('input.ts');
+      const parseSettings2 = createParseSettings('input.ts');
+
+      expect(parseSettings1.tsconfigMatchCache).toBe(
+        parseSettings2.tsconfigMatchCache,
+      );
+    });
+  });
+});