fix(compiler): don’t type check templates with `skipTemplateCodegen` (#19909)

This change is needed to prevent users’ builds from breaking.

If a user sets `fullTemlateTypeCheck` to true, we will
continue to check the templates even when `skipTemplateCodegen` is true
as well.

Related to #19906

PR Close #19909

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

@@ -426,6 +426,12 @@ export class TsCompilerAotCompilerTypeCheckHostAdapter implements ts.CompilerHos
   }
 
   isSourceFile(filePath: string): boolean {
+    // Don't generate any files nor typecheck them
+    // if skipTemplateCodegen is set and fullTemplateTypeCheck is not yet set,
+    // for backwards compatibility.
+    if (this.options.skipTemplateCodegen && !this.options.fullTemplateTypeCheck) {
+      return false;
+    }
     // If we have a summary from a previous compilation,
     // treat the file never as a source file.
     if (this.librarySummaries.has(filePath)) {

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

@@ -181,11 +181,13 @@ function createVariableStatementForDeclarations(declarations: Declaration[]): ts
       /* modifiers */ undefined, ts.createVariableDeclarationList(varDecls, ts.NodeFlags.Const));
 }
 
-export function getExpressionLoweringTransformFactory(requestsMap: RequestsMap):
-    (context: ts.TransformationContext) => (sourceFile: ts.SourceFile) => ts.SourceFile {
+export function getExpressionLoweringTransformFactory(
+    requestsMap: RequestsMap, program: ts.Program): (context: ts.TransformationContext) =>
+    (sourceFile: ts.SourceFile) => ts.SourceFile {
   // Return the factory
   return (context: ts.TransformationContext) => (sourceFile: ts.SourceFile): ts.SourceFile => {
-    const requests = requestsMap.getRequests(sourceFile);
+    // We need to use the original SourceFile for reading metadata, and not the transformed one.
+    const requests = requestsMap.getRequests(program.getSourceFile(sourceFile.fileName));
     if (requests && requests.size) {
       return transformSourceFile(sourceFile, requests, context);
     }

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

@@ -386,7 +386,7 @@ class AngularCompilerProgram implements Program {
       customTransformers?: CustomTransformers): ts.CustomTransformers {
     const beforeTs: ts.TransformerFactory<ts.SourceFile>[] = [];
     if (!this.options.disableExpressionLowering) {
-      beforeTs.push(getExpressionLoweringTransformFactory(this.metadataCache));
+      beforeTs.push(getExpressionLoweringTransformFactory(this.metadataCache, this.tsProgram));
     }
     beforeTs.push(getAngularEmitterTransformFactory(genFiles));
     if (customTransformers && customTransformers.beforeTs) {
@@ -754,7 +754,7 @@ export function createSrcToOutPathMapper(
 export function i18nExtract(
     formatName: string | null, outFile: string | null, host: ts.CompilerHost,
     options: CompilerOptions, bundle: MessageBundle): string[] {
-  formatName = formatName || 'null';
+  formatName = formatName || 'xlf';
   // Checks the format and returns the extension
   const ext = i18nGetExtension(formatName);
   const content = i18nSerialize(bundle, formatName, options);
@@ -788,7 +788,7 @@ export function i18nSerialize(
 }
 
 export function i18nGetExtension(formatName: string): string {
-  const format = (formatName || 'xlf').toLowerCase();
+  const format = formatName.toLowerCase();
 
   switch (format) {
     case 'xmb':

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

@@ -181,13 +181,15 @@ function convert(annotatedSource: string) {
       [fileName], {module: ts.ModuleKind.CommonJS, target: ts.ScriptTarget.ES2017}, host);
   const moduleSourceFile = program.getSourceFile(fileName);
   const transformers: ts.CustomTransformers = {
-    before: [getExpressionLoweringTransformFactory({
-      getRequests(sourceFile: ts.SourceFile): RequestLocationMap{
-        if (sourceFile.fileName == moduleSourceFile.fileName) {
-          return requests;
-        } else {return new Map();}
-      }
-    })]
+    before: [getExpressionLoweringTransformFactory(
+        {
+          getRequests(sourceFile: ts.SourceFile): RequestLocationMap{
+            if (sourceFile.fileName == moduleSourceFile.fileName) {
+              return requests;
+            } else {return new Map();}
+          }
+        },
+        program)]
   };
   let result: string = '';
   const emitResult = program.emit(

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

@@ -11,7 +11,7 @@ import * as fs from 'fs';
 import * as path from 'path';
 import * as ts from 'typescript';
 
-import {CompilerHost, LazyRoute} from '../../src/transformers/api';
+import {CompilerHost, EmitFlags, LazyRoute} from '../../src/transformers/api';
 import {createSrcToOutPathMapper} from '../../src/transformers/program';
 import {GENERATED_FILES, StructureIsReused, tsStructureIsReused} from '../../src/transformers/util';
 import {TestSupport, expectNoDiagnosticsInProgram, setup} from '../test_support';
@@ -309,11 +309,35 @@ describe('ng program', () => {
     });
   });
 
-  it('should typecheck templates even if skipTemplateCodegen is set', () => {
+  it('should not typecheck templates if skipTemplateCodegen is set but fullTemplateTypeCheck is not',
+     () => {
+       testSupport.writeFiles({
+         'src/main.ts': `
+        import {NgModule} from '@angular/core';
+
+        @NgModule(() => {if (1==1) return null as any;})
+        export class SomeClassWithInvalidMetadata {}
+      `,
+       });
+       const options = testSupport.createCompilerOptions({skipTemplateCodegen: true});
+       const host = ng.createCompilerHost({options});
+       const program = ng.createProgram(
+           {rootNames: [path.resolve(testSupport.basePath, 'src/main.ts')], options, host});
+       expectNoDiagnosticsInProgram(options, program);
+       const emitResult = program.emit({emitFlags: EmitFlags.All});
+       expect(emitResult.diagnostics.length).toBe(0);
+
+       testSupport.shouldExist('built/src/main.metadata.json');
+     });
+
+  it('should typecheck templates if skipTemplateCodegen and fullTemplateTypeCheck is set', () => {
     testSupport.writeFiles({
       'src/main.ts': createModuleAndCompSource('main', `{{nonExistent}}`),
     });
-    const options = testSupport.createCompilerOptions({skipTemplateCodegen: true});
+    const options = testSupport.createCompilerOptions({
+      skipTemplateCodegen: true,
+      fullTemplateTypeCheck: true,
+    });
     const host = ng.createCompilerHost({options});
     const program = ng.createProgram(
         {rootNames: [path.resolve(testSupport.basePath, 'src/main.ts')], options, host});