lit · rictic · Aug 27, 2025 · Aug 22, 2025 · Aug 27, 2025 · Aug 27, 2025
@@ -0,0 +1,5 @@
+---
+'@lit-labs/tsserver-plugin': patch
+---
+
+Optimize tests a bit.
@@ -3,25 +3,23 @@ import path from 'node:path';
 import {describe as suite, test} from 'node:test';
 import * as ts from 'typescript';
 import {getLitExpressionType} from '../../lib/type-helpers/lit-expression-type.js';
+import {getReusableTestProjectService} from '../project-service.js';
 
-// Ensure the declarations are part of the program (side-effect import only).
-import './fake-lit-html-types.js';
-
-// Helper to build a Program including our fake lit-html types file.
-function buildProgram(): ts.Program {
-  // Build the path relative to the package root (cwd during tests) to avoid
-  // accidentally duplicating path segments. The previous value incorrectly
-  // prefixed the repository path twice when running inside the package.
-  const fakeTypesPath = path.resolve('src/test/lib/fake-lit-html-types.ts');
-  const options: ts.CompilerOptions = {
-    target: ts.ScriptTarget.ES2022,
-    module: ts.ModuleKind.NodeNext,
-    moduleResolution: ts.ModuleResolutionKind.NodeNext,
-    strict: true,
-    esModuleInterop: true,
-    skipLibCheck: true,
-  };
-  return ts.createProgram([fakeTypesPath], options);
+function getProgram(): ts.Program {
+  using cleanup = getReusableTestProjectService();
+  const projectService = cleanup.projectService;
+  const expressionTypesPath = path.resolve(
+    'test-files/basic-templates/src/expression-types.ts'
+  );
+  const result = projectService.openClientFile(expressionTypesPath);
+  if (!result.configFileName) {
+    throw new Error('Did not associate file with a config');
+  }
+  const info = projectService.getScriptInfo(expressionTypesPath)!;
+  const project = info.containingProjects[0];
+  const program = project.getLanguageService().getProgram();
+  if (!program) throw new Error('No program');
+  return program;
 }
 
 function getExportType(
@@ -30,7 +28,7 @@ function getExportType(
 ): ts.Type | undefined {
   const sourceFiles = program.getSourceFiles();
   const fakeFile = sourceFiles.find((f) =>
-    /fake-lit-html-types\.ts$/.test(f.fileName)
+    /expression-types\.ts$/.test(f.fileName)
   );
   if (!fakeFile) return undefined;
   const checker = program.getTypeChecker();
@@ -54,7 +52,7 @@ suite('getLitExpressionType', () => {
   }
 
   test('sentinel unique symbols map to any', () => {
-    const program = buildProgram();
+    const program = getProgram();
     const checker = program.getTypeChecker();
     // Use the direct exported sentinel symbols so the type has the correct symbol name.
     const noChangeType = getExportType(program, 'noChange');
@@ -70,7 +68,7 @@ suite('getLitExpressionType', () => {
   });
 
   test('DirectiveResult unwraps to render return type (primitive)', () => {
-    const program = buildProgram();
+    const program = getProgram();
     const checker = program.getTypeChecker();
     const directiveResultNumber = getExportType(
       program,
@@ -86,7 +84,7 @@ suite('getLitExpressionType', () => {
   });
 
   test('DirectiveResult unwraps to union of render return types', () => {
-    const program = buildProgram();
+    const program = getProgram();
     const checker = program.getTypeChecker();
     const directiveResultUnion = getExportType(program, 'directiveResultUnion');
     assert.strictEqual(
@@ -110,7 +108,7 @@ suite('getLitExpressionType', () => {
   });
 
   test('Union containing DirectiveResult unwraps only that member', () => {
-    const program = buildProgram();
+    const program = getProgram();
     const checker = program.getTypeChecker();
     const mixed = getExportType(program, 'directiveResultOrString');
     assert.strictEqual(
@@ -134,7 +132,7 @@ suite('getLitExpressionType', () => {
   });
 
   test('Union with sentinel symbol filters out the sentinel', () => {
-    const program = buildProgram();
+    const program = getProgram();
     const checker = program.getTypeChecker();
     const sentinelUnion = getExportType(program, 'sentinelUnion');
     const transformed = getLitExpressionType(sentinelUnion!, ts, program);
@@ -146,21 +144,21 @@ suite('getLitExpressionType', () => {
   });
 
   test('Plain non-special type is unchanged', () => {
-    const plainProgram = buildProgram();
-    const checker = plainProgram.getTypeChecker();
-    const plainNumber = getExportType(plainProgram, 'plainNumber');
+    const program = getProgram();
+    const checker = program.getTypeChecker();
+    const plainNumber = getExportType(program, 'plainNumber');
     assert.strictEqual(checker.typeToString(plainNumber!), '123');
-    const result = getLitExpressionType(plainNumber!, ts, plainProgram);
+    const result = getLitExpressionType(plainNumber!, ts, program);
     assert.strictEqual(result, plainNumber);
     // literal 123 keeps its literal type.
     assert.strictEqual(checker.typeToString(result), '123');
   });
 
   test('Union without special values is unchanged', () => {
-    const plainProgram = buildProgram();
-    const checker = plainProgram.getTypeChecker();
-    const plainUnion = getExportType(plainProgram, 'plainUnion');
-    const result = getLitExpressionType(plainUnion!, ts, plainProgram);
+    const program = getProgram();
+    const checker = program.getTypeChecker();
+    const plainUnion = getExportType(program, 'plainUnion');
+    const result = getLitExpressionType(plainUnion!, ts, program);
     assert.strictEqual(result, plainUnion);
     assert.strictEqual(
       normalizeUnion(checker.typeToString(plainUnion!)),
@@ -171,39 +169,27 @@ suite('getLitExpressionType', () => {
   test('Sentinel-like symbol outside lit-html scope not treated as special', () => {
     // Create a synthetic unique symbol type named noChange but from a different file.
     const sourceText = 'export const noChange = Symbol("local");';
-    const tempFile = path.resolve('src/test/lib/local-file.ts');
-    const compilerOptions: ts.CompilerOptions = {
-      target: ts.ScriptTarget.ES2022,
-      module: ts.ModuleKind.NodeNext,
-      moduleResolution: ts.ModuleResolutionKind.NodeNext,
-      strict: true,
-    };
-    const host = ts.createCompilerHost(compilerOptions);
-    host.readFile = (fileName) => {
-      if (fileName === tempFile) return sourceText;
-      return ts.sys.readFile(fileName);
-    };
-    host.fileExists = (fileName) => {
-      if (fileName === tempFile) return true;
-      return ts.sys.fileExists(fileName);
-    };
-    const shadowProgram = ts.createProgram(
-      [path.resolve('src/test/lib/fake-lit-html-types.ts'), tempFile],
-      compilerOptions,
-      host
+    const tempFile = path.resolve(
+      'test-files/basic-templates/src/local-sentinel.ts'
     );
-    const checker = shadowProgram.getTypeChecker();
-    const sf = shadowProgram
+    using cleanup = getReusableTestProjectService();
+    const projectService = cleanup.projectService;
+    // Simulate the file existing in memory only: open with content.
+    projectService.openClientFile(tempFile, sourceText);
+    const info = projectService.getScriptInfo(tempFile)!;
+    const project = info.containingProjects[0];
+    const program = project.getLanguageService().getProgram()!;
+    const checker = program.getTypeChecker();
+    const sf = program
       .getSourceFiles()
-      .find((f) => /local-file\.ts$/.test(f.fileName))!;
+      .find((f) => /local-sentinel\.ts$/.test(f.fileName))!;
     const moduleSymbol = checker.getSymbolAtLocation(sf)!;
     const localSymbol = checker
       .getExportsOfModule(moduleSymbol)
       .find((s) => s.getEscapedName() === 'noChange')!;
     const localType = checker.getTypeOfSymbol(localSymbol);
     assert.ok(localType, 'got localtype');
-    const result = getLitExpressionType(localType, ts, shadowProgram);
-    // Should be unchanged (unique symbol stays unique symbol) not widened to any.
+    const result = getLitExpressionType(localType, ts, program);
     assert.strictEqual(result, localType);
     assert.strictEqual(checker.typeToString(localType), 'unique symbol');
     assert.strictEqual(checker.typeToString(result), 'unique symbol');

@@ -1,7 +1,7 @@
 import assert from 'node:assert';
 import * as path from 'node:path';
 import {describe as suite, test} from 'node:test';
-import {createTestProjectService} from '../project-service.js';
+import {getReusableTestProjectService} from '../project-service.js';
 import {getLitTemplateExpressions} from '@lit-labs/analyzer/lib/lit/template.js';
 import ts from 'typescript';
 
@@ -10,7 +10,8 @@ function setupLanguageService(pathName: string): {
   program: ts.Program;
   testSourceFile: ts.SourceFile;
 } {
-  const projectService = createTestProjectService();
+  using cleanup = getReusableTestProjectService();
+  const projectService = cleanup.projectService;
   const result = projectService.openClientFile(pathName);
   assert.ok(result.configFileName);
 

@@ -2,9 +2,7 @@ import ts from 'typescript';
 
 /* eslint-disable @typescript-eslint/no-explicit-any */
 
-const fakeFileWatcher: ts.FileWatcher = {
-  close() {},
-};
+const fakeFileWatcher: ts.FileWatcher = {close() {}};
 
 const serverHost: ts.server.ServerHost = {
   ...ts.sys,
@@ -29,23 +27,29 @@ const serverHost: ts.server.ServerHost = {
   },
 
   setTimeout(
-    _callback: (...args: any[]) => void,
-    _ms: number,
-    ..._args: any[]
+    callback: (...args: any[]) => void,
+    ms: number,
+    ...args: any[]
   ): any {
-    throw new Error('Method not implemented.');
+    return globalThis.setTimeout(callback, ms, ...args);
   },
 
-  clearTimeout(_timeoutId: any): void {
-    throw new Error('Method not implemented.');
+  clearTimeout(timeoutId: any): void {
+    globalThis.clearTimeout(timeoutId);
   },
 
-  setImmediate(_callback: (...args: any[]) => void, ..._args: any[]): any {
-    throw new Error('Method not implemented.');
+  setImmediate(callback: (...args: any[]) => void, ...args: any[]): any {
+    return (globalThis as any).setImmediate
+      ? (globalThis as any).setImmediate(callback, ...args)
+      : globalThis.setTimeout(callback, 0, ...args);
   },
 
-  clearImmediate(_timeoutId: any): void {
-    throw new Error('Method not implemented.');
+  clearImmediate(timeoutId: any): void {
+    if ((globalThis as any).clearImmediate) {
+      (globalThis as any).clearImmediate(timeoutId);
+    } else {
+      globalThis.clearTimeout(timeoutId);
+    }
   },
 };
 
@@ -91,3 +95,19 @@ export const createTestProjectService = () => {
   });
   return projectService;
 };
+
+let reusableProjectService: ts.server.ProjectService | undefined;
+export const getReusableTestProjectService = () => {
+  if (!reusableProjectService) {
+    reusableProjectService = createTestProjectService();
+  }
+  const projectService = reusableProjectService;
+  return {
+    projectService,
+    [Symbol.dispose]() {
+      for (const [path] of projectService.openFiles) {
+        projectService.closeClientFile(path);
+      }
+    },
+  };
+};
@@ -1,12 +1,13 @@
 import assert from 'node:assert';
 import * as path from 'node:path';
 import {describe as suite, test} from 'node:test';
-import {createTestProjectService} from '../project-service.js';
 import {LitDiagnosticCode} from '../../lib/diagnostic-codes.js';
+import {getReusableTestProjectService} from '../project-service.js';
 
 suite('no-binding-like-attribute-names', () => {
   test('Reports on property-binding-like attribute names', () => {
-    const projectService = createTestProjectService();
+    using cleanup = getReusableTestProjectService();
+    const projectService = cleanup.projectService;
 
     const pathName = path.resolve(
       'test-files/basic-templates/src/bad-attribute-name.ts'

@@ -7,7 +7,7 @@
 import assert from 'node:assert';
 import * as path from 'node:path';
 import {describe as suite, test} from 'node:test';
-import {createTestProjectService} from '../project-service.js';
+import {getReusableTestProjectService} from '../project-service.js';
 import {LitDiagnosticCode} from '../../lib/diagnostic-codes.js';
 import type {Diagnostic} from 'typescript';
 
@@ -21,7 +21,8 @@ function assertDiagnosticMessages(
 
 suite('no-unassignable-property-bindings', () => {
   test('Unknown property diagnostic', () => {
-    const projectService = createTestProjectService();
+    using cleanup = getReusableTestProjectService();
+    const projectService = cleanup.projectService;
     const file = path.resolve(
       'test-files/basic-templates/src/property-binding-unknown.ts'
     );
@@ -40,7 +41,8 @@ suite('no-unassignable-property-bindings', () => {
   });
 
   test('No diagnostics for assignable bindings', () => {
-    const projectService = createTestProjectService();
+    using cleanup = getReusableTestProjectService();
+    const projectService = cleanup.projectService;
     const file = path.resolve(
       'test-files/basic-templates/src/property-binding-assignable.ts'
     );
@@ -60,7 +62,8 @@ suite('no-unassignable-property-bindings', () => {
   });
 
   test('Unassignable bindings produce diagnostics', () => {
-    const projectService = createTestProjectService();
+    using cleanup = getReusableTestProjectService();
+    const projectService = cleanup.projectService;
     const file = path.resolve(
       'test-files/basic-templates/src/property-binding-unassignable.ts'
     );