refactor(compiler-cli): speed up compiler tests by caching Angular (#54650)

Currently the `makeProgram` utility from `ngtsc/testing` does not use
the test host by default- optimizing for source file caching.

Additionally, the host can be updated to attempt caching of the `.d.ts`
files from `@angular/core`— whether that's fake core, or the real core-
is irrelevant. We are never caching if these changes between tests, so
correctness is guaranteed.

This commit reduces the type check test times form 80s to just 11
seconds, faster than what it was before with `fake_core`. The ngtsc
tests also run significantly faster. From 40s to 30s

PR Close #54650

Author: devversion

packages/compiler-cli/src/ngtsc/testing/src/cached_source_files.ts

@@ -7,6 +7,7 @@
  */
 
 import ts from 'typescript';
+
 import {basename} from '../../file_system';
 
 // A cache of source files that are typically used across tests and are expensive to parse.
@@ -28,7 +29,8 @@ let sourceFileCache = new Map<string, ts.SourceFile>();
  */
 export function getCachedSourceFile(
     fileName: string, load: () => string | undefined): ts.SourceFile|null {
-  if (!/^lib\..+\.d\.ts$/.test(basename(fileName))) {
+  if (!/^lib\..+\.d\.ts$/.test(basename(fileName)) &&
+      !/\/node_modules\/(@angular|rxjs)\//.test(fileName)) {
     return null;
   }
 

packages/compiler-cli/src/ngtsc/testing/src/utils.ts

@@ -14,6 +14,8 @@ import {AbsoluteFsPath, dirname, getFileSystem, getSourceFileOrError, NgtscCompi
 import {DeclarationNode} from '../../reflection';
 import {getTokenAtPosition} from '../../util/src/typescript';
 
+import {NgtscTestCompilerHost} from './compiler_host';
+
 export function makeProgram(
     files: {name: AbsoluteFsPath, contents: string, isRoot?: boolean}[],
     options?: ts.CompilerOptions, host?: ts.CompilerHost, checkForErrors: boolean = true):
@@ -30,7 +32,7 @@ export function makeProgram(
     moduleResolution: ts.ModuleResolutionKind.Node10,
     ...options
   };
-  const compilerHost = new NgtscCompilerHost(fs, compilerOptions);
+  const compilerHost = new NgtscTestCompilerHost(fs, compilerOptions);
   const rootNames = files.filter(file => file.isRoot !== false)
                         .map(file => compilerHost.getCanonicalFileName(file.name));
   const program = ts.createProgram(rootNames, compilerOptions, compilerHost);
@@ -110,7 +112,7 @@ export function walkForDeclarations(name: string, rootNode: ts.Node): Declaratio
   return chosenDecls;
 }
 
-export function isNamedDeclaration(node: ts.Node): node is ts.Declaration&{name: ts.Identifier} {
+export function isNamedDeclaration(node: ts.Node): node is(ts.Declaration & {name: ts.Identifier}) {
   const namedNode = node as {name?: ts.Identifier};
   return namedNode.name !== undefined && ts.isIdentifier(namedNode.name);
 }

packages/compiler-cli/src/ngtsc/typecheck/testing/index.ts

@@ -437,7 +437,13 @@ export function setup(targets: TypeCheckingTarget[], overrides: {
   const config = overrides.config ?? {};
 
   const {program, host, options} = makeProgram(
-      files, {strictNullChecks: true, noImplicitAny: true, ...opts}, /* host */ undefined,
+      files, {
+        strictNullChecks: true,
+        skipLibCheck: true,
+        noImplicitAny: true,
+        ...opts,
+      },
+      /* host */ undefined,
       /* checkForErrors */ false);
   const checker = program.getTypeChecker();
   const logicalFs = new LogicalFileSystem(getRootDirs(host, options), host);

packages/language-service/test/BUILD.bazel

@@ -25,6 +25,7 @@ jasmine_node_test(
         "//packages/core:npm_package",
         "@npm//rxjs",
     ],
+    shard_count = 4,
     deps = [
         ":test_lib",
     ],

packages/language-service/testing/src/language_service_test_cache.ts

@@ -0,0 +1,50 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {getCachedSourceFile} from '@angular/compiler-cli/src/ngtsc/testing';
+import ts from 'typescript';
+
+interface TsProjectWithInternals {
+  // typescript/src/server/project.ts#ConfiguredProject
+  setCompilerHost?(host: ts.CompilerHost): void;
+}
+
+let patchedLanguageServiceProjectHost = false;
+
+/**
+ * Updates `ts.server.Project` to use efficient test caching of source files
+ * that aren't expected to be changed. E.g. the default libs.
+ */
+export function patchLanguageServiceProjectsWithTestHost() {
+  if (patchedLanguageServiceProjectHost) {
+    return;
+  }
+  patchedLanguageServiceProjectHost = true;
+
+  (ts.server.Project.prototype as TsProjectWithInternals).setCompilerHost = (host) => {
+    const _originalHostGetSourceFile = host.getSourceFile;
+    const _originalHostGetSourceFileByPath = host.getSourceFileByPath;
+
+    host.getSourceFile =
+        (fileName, languageVersionOrOptions, onError, shouldCreateNewSourceFile) => {
+          return getCachedSourceFile(fileName, () => host.readFile(fileName)) ??
+              _originalHostGetSourceFile.call(
+                  host, fileName, languageVersionOrOptions, onError, shouldCreateNewSourceFile);
+        };
+
+    if (_originalHostGetSourceFileByPath !== undefined) {
+      host.getSourceFileByPath =
+          (fileName, path, languageVersionOrOptions, onError, shouldCreateNewSourceFile) => {
+            return getCachedSourceFile(fileName, () => host.readFile(fileName)) ??
+                _originalHostGetSourceFileByPath.call(
+                    host, fileName, path, languageVersionOrOptions, onError,
+                    shouldCreateNewSourceFile);
+          };
+    }
+  };
+}

packages/language-service/testing/src/project.ts

@@ -14,6 +14,7 @@ import ts from 'typescript/lib/tsserverlibrary';
 import {LanguageService} from '../../src/language_service';
 
 import {OpenBuffer} from './buffer';
+import {patchLanguageServiceProjectsWithTestHost} from './language_service_test_cache';
 
 export type ProjectFiles = {
   [fileName: string]: string;
@@ -76,14 +77,17 @@ export class Project {
 
     writeTsconfig(fs, tsConfigPath, entryFiles, angularCompilerOptions, tsCompilerOptions);
 
+    patchLanguageServiceProjectsWithTestHost();
+
     // Ensure the project is live in the ProjectService.
+    // This creates the `ts.Program` by configuring the project and loading it!
     projectService.openClientFile(entryFiles[0]);
     projectService.closeClientFile(entryFiles[0]);
 
     return new Project(projectName, projectService, tsConfigPath);
   }
 
-  constructor(
+  private constructor(
       readonly name: string, private projectService: ts.server.ProjectService,
       private tsConfigPath: AbsoluteFsPath) {
     // LS for project