typescript-eslint · JoshuaKGoldberg · Apr 15, 2024 · Apr 1, 2024 · Apr 1, 2024 · Apr 1, 2024
diff --git a/docs/packages/TypeScript_ESTree.mdx b/docs/packages/TypeScript_ESTree.mdx
@@ -277,9 +277,14 @@ interface ParseAndGenerateServicesOptions extends ParseOptions {
  */
 interface ProjectServiceOptions {
   /**
-   * Globs of files to allow running with the default inferred project settings.
+   * Globs of files to allow running with the default project compiler options.
    */
   allowDefaultProjectForFiles?: string[];
+
+  /**
+   * Path to a TSConfig to use instead of TypeScript's default project configuration.
+   */
+  defaultProject?: string;
 }
 
 interface ParserServices {

diff --git a/packages/typescript-estree/src/create-program/createProjectService.ts b/packages/typescript-estree/src/create-program/createProjectService.ts
@@ -1,4 +1,6 @@
 /* eslint-disable @typescript-eslint/no-empty-function -- for TypeScript APIs*/
+import os from 'node:os';
+
 import type * as ts from 'typescript/lib/tsserverlibrary';
 
 import type { ProjectServiceOptions } from '../parser-options';
@@ -58,6 +60,42 @@ export function createProjectService(
     jsDocParsingMode,
   });
 
+  if (typeof options === 'object' && options.defaultProject) {
+    let configRead;
+
+    try {
+      configRead = tsserver.readConfigFile(
+        options.defaultProject,
+        system.readFile,
+      );
+    } catch (error) {
+      throw new Error(
+        `Could not parse default project '${options.defaultProject}': ${(error as Error).message}`,
+      );
+    }
+
+    if (configRead.error) {
+      throw new Error(
+        `Could not read default project '${options.defaultProject}': ${tsserver.formatDiagnostic(
+          configRead.error,
+          {
+            getCurrentDirectory: system.getCurrentDirectory,
+            getCanonicalFileName: fileName => fileName,
+            getNewLine: () => os.EOL,
+          },
+        )}`,
+      );
+    }
+
+    service.setCompilerOptionsForInferredProjects(
+      (
+        configRead.config as {
+          compilerOptions: ts.server.protocol.InferredProjectCompilerOptions;
+        }
+      ).compilerOptions,
+    );
+  }
+
   return {
     allowDefaultProjectForFiles:
       typeof options === 'object'

diff --git a/packages/typescript-estree/src/parser-options.ts b/packages/typescript-estree/src/parser-options.ts
@@ -106,9 +106,14 @@ interface ParseOptions {
  */
 export interface ProjectServiceOptions {
   /**
-   * Globs of files to allow running with the default inferred project settings.
+   * Globs of files to allow running with the default project compiler options.
    */
   allowDefaultProjectForFiles?: string[];
+
+  /**
+   * Path to a TSConfig to use instead of TypeScript's default project configuration.
+   */
+  defaultProject?: string;
 }
 
 interface ParseAndGenerateServicesOptions extends ParseOptions {

diff --git a/packages/typescript-estree/tests/lib/createProjectService.test.ts b/packages/typescript-estree/tests/lib/createProjectService.test.ts
@@ -1,5 +1,21 @@
+import * as ts from 'typescript';
+
 import { createProjectService } from '../../src/create-program/createProjectService';
 
+const mockReadConfigFile = jest.fn();
+const mockSetCompilerOptionsForInferredProjects = jest.fn();
+
+jest.mock('typescript/lib/tsserverlibrary', () => ({
+  ...jest.requireActual('typescript/lib/tsserverlibrary'),
+  readConfigFile: mockReadConfigFile,
+  server: {
+    ProjectService: class {
+      setCompilerOptionsForInferredProjects =
+        mockSetCompilerOptionsForInferredProjects;
+    },
+  },
+}));
+
 describe('createProjectService', () => {
   it('sets allowDefaultProjectForFiles when options.allowDefaultProjectForFiles is defined', () => {
     const allowDefaultProjectForFiles = ['./*.js'];
@@ -18,4 +34,64 @@ describe('createProjectService', () => {
 
     expect(settings.allowDefaultProjectForFiles).toBeUndefined();
   });
+
+  it('throws an error when options.defaultProject is set and readConfigFile returns an error', () => {
+    mockReadConfigFile.mockReturnValue({
+      error: {
+        category: ts.DiagnosticCategory.Error,
+        code: 1234,
+        file: ts.createSourceFile('./tsconfig.json', '', {
+          languageVersion: ts.ScriptTarget.Latest,
+        }),
+        start: 0,
+        length: 0,
+        messageText: 'Oh no!',
+      } satisfies ts.Diagnostic,
+    });
+
+    expect(() =>
+      createProjectService(
+        {
+          allowDefaultProjectForFiles: ['file.js'],
+          defaultProject: './tsconfig.json',
+        },
+        undefined,
+      ),
+    ).toThrow(
+      /Could not read default project '\.\/tsconfig.json': .+ error TS1234: Oh no!/,
+    );
+  });
+
+  it('throws an error when options.defaultProject is set and readConfigFile throws an error', () => {
+    mockReadConfigFile.mockImplementation(() => {
+      throw new Error('Oh no!');
+    });
+
+    expect(() =>
+      createProjectService(
+        {
+          allowDefaultProjectForFiles: ['file.js'],
+          defaultProject: './tsconfig.json',
+        },
+        undefined,
+      ),
+    ).toThrow("Could not parse default project './tsconfig.json': Oh no!");
+  });
+
+  it('uses the default projects compiler options when options.defaultProject is set and readConfigFile succeeds', () => {
+    const compilerOptions = { strict: true };
+    mockReadConfigFile.mockReturnValue({ config: { compilerOptions } });
+
+    const { service } = createProjectService(
+      {
+        allowDefaultProjectForFiles: ['file.js'],
+        defaultProject: './tsconfig.json',
+      },
+      undefined,
+    );
+
+    expect(service.setCompilerOptionsForInferredProjects).toHaveBeenCalledWith(
+      compilerOptions,
+    );
+  });
 });