test(compiler-cli): improve testing harness for incremental compilation (#25275)

In tsc 3.0 the check that enables program structure reuse in tryReuseStructureFromOldProgram has changed
and now uses identity comparison on arrays within CompilerOptions. Since we recreate the options
on each incremental compilation, we now fail this check.

After this change the default set of options is reused in between incremental compilations, but we still
allow options to be overriden if needed.

PR Close #25275

packages/compiler-cli/src/transformers/compiler_host.ts

@@ -393,9 +393,6 @@ export class TsCompilerAotCompilerTypeCheckHostAdapter implements ts.CompilerHos
   getSourceFile(
       fileName: string, languageVersion: ts.ScriptTarget,
       onError?: ((message: string) => void)|undefined): ts.SourceFile {
-        if (fileName.endsWith('@angular/core/src/di/injection_token.d.ts')) {
-          debugger;
-        }
     // Note: Don't exit early in this method to make sure
     // we always have up to date references on the file!
     let genFileNames: string[] = [];

packages/compiler-cli/test/test_support.ts

@@ -49,6 +49,33 @@ export interface TestSupport {
 }
 
 function createTestSupportFor(basePath: string) {
+  // Typescript uses identity comparison on `paths` and other arrays in order to determine
+  // if program structure can be reused for incremental compilation, so we reuse the default
+  // values unless overriden, and freeze them so that they can't be accidentaly changed somewhere
+  // in tests.
+  const defaultCompilerOptions = {
+    basePath,
+    'experimentalDecorators': true,
+    'skipLibCheck': true,
+    'strict': true,
+    'strictPropertyInitialization': false,
+    'types': Object.freeze<string>([]) as string[],
+    'outDir': path.resolve(basePath, 'built'),
+    'rootDir': basePath,
+    'baseUrl': basePath,
+    'declaration': true,
+    'target': ts.ScriptTarget.ES5,
+    'module': ts.ModuleKind.ES2015,
+    'moduleResolution': ts.ModuleResolutionKind.NodeJs,
+    'lib': Object.freeze([
+      path.resolve(basePath, 'node_modules/typescript/lib/lib.es6.d.ts'),
+    ]) as string[],
+    // clang-format off
+    'paths': Object.freeze({'@angular/*': ['./node_modules/@angular/*']}) as {[index: string]: string[]}
+    // clang-format on
+  };
+
+
   return {basePath, write, writeFiles, createCompilerOptions, shouldExist, shouldNotExist};
 
   function write(fileName: string, content: string) {
@@ -66,25 +93,7 @@ function createTestSupportFor(basePath: string) {
   }
 
   function createCompilerOptions(overrideOptions: ng.CompilerOptions = {}): ng.CompilerOptions {
-    return {
+    return {...defaultCompilerOptions, ...overrideOptions};
-      basePath,
-      'experimentalDecorators': true,
-      'skipLibCheck': true,
-      'strict': true,
-      'strictPropertyInitialization': false,
-      'types': [],
-      'outDir': path.resolve(basePath, 'built'),
-      'rootDir': basePath,
-      'baseUrl': basePath,
-      'declaration': true,
-      'target': ts.ScriptTarget.ES5,
-      'module': ts.ModuleKind.ES2015,
-      'moduleResolution': ts.ModuleResolutionKind.NodeJs,
-      'lib': [
-        path.resolve(basePath, 'node_modules/typescript/lib/lib.es6.d.ts'),
-      ],
-      'paths': {'@angular/*': ['./node_modules/@angular/*']}, ...overrideOptions,
-    };
   }
 
   function shouldExist(fileName: string) {

packages/compiler-cli/test/transformers/program_spec.ts

@@ -59,7 +59,7 @@ describe('ng program', () => {
 
   function compile(
       oldProgram?: ng.Program, overrideOptions?: ng.CompilerOptions, rootNames?: string[],
-      host?: CompilerHost): {program: ng.Program, emitResult: ts.EmitResult, host: ng.CompilerHost} {
+      host?: CompilerHost): {program: ng.Program, emitResult: ts.EmitResult} {
     const options = testSupport.createCompilerOptions(overrideOptions);
     if (!rootNames) {
       rootNames = [path.resolve(testSupport.basePath, 'src/index.ts')];
@@ -75,7 +75,7 @@ describe('ng program', () => {
     });
     expectNoDiagnosticsInProgram(options, program);
     const emitResult = program.emit();
-    return {emitResult, program, host};
+    return {emitResult, program};
   }
 
   function createWatchModeHost(): ng.CompilerHost {
@@ -85,17 +85,16 @@ describe('ng program', () => {
     const originalGetSourceFile = host.getSourceFile;
     const cache = new Map<string, ts.SourceFile>();
     host.getSourceFile = function(fileName: string): ts.SourceFile {
-      if (fileName.endsWith('@angular/core/src/di/injection_token.d.ts')) {
-        debugger;
-      }
       const sf = originalGetSourceFile.call(host, fileName) as ts.SourceFile;
-      if (sf && cache.has(sf.fileName)) {
+      if (sf) {
-        const oldSf = cache.get(sf.fileName)!;
+        if (cache.has(sf.fileName)) {
+          const oldSf = cache.get(sf.fileName) !;
           if (oldSf.getFullText() === sf.getFullText()) {
             return oldSf;
           }
         }
-      sf && cache.set(sf.fileName, sf);
+        cache.set(sf.fileName, sf);
+      }
       return sf;
     };
     return host;
@@ -290,7 +289,10 @@ describe('ng program', () => {
           .toBe(false);
     });
 
-    describe('reuse tests', () => {
+    describe(
+        'verify that program structure is reused within tsc in order to speed up incremental compilation',
+        () => {
+
           it('should reuse the old ts program completely if nothing changed', () => {
             testSupport.writeFiles({'src/index.ts': createModuleAndCompSource('main')});
             const host = createWatchModeHost();
@@ -298,12 +300,12 @@ describe('ng program', () => {
             // and therefore changes the structure again
             const p1 = compile(undefined, undefined, undefined, host).program;
             const p2 = compile(p1, undefined, undefined, host).program;
-        debugger;
             compile(p2, undefined, undefined, host);
             expect(tsStructureIsReused(p2.getTsProgram())).toBe(StructureIsReused.Completely);
           });
 
-      it('should reuse the old ts program completely if a template or a ts file changed', () => {
+          it('should reuse the old ts program completely if a template or a ts file changed',
+             () => {
                const host = createWatchModeHost();
                testSupport.writeFiles({
                  'src/main.ts': createModuleAndCompSource('main', 'main.html'),