fix(ngcc): do not inline source-maps for non-inline typings source-maps (angular#37363)

Inline source-maps in typings files can impact IDE performance
so ngcc should only add such maps if the original typings file
contains inline source-maps.

Fixes angular#37324

PR Close angular#37363

Author: petebacondarwin

packages/compiler-cli/ngcc/src/rendering/source_maps.ts

@@ -42,8 +42,16 @@ export function renderSourceAndMap(
 
     const rawMergedMap: RawSourceMap = generatedFile.renderFlattenedSourceMap();
     const mergedMap = fromObject(rawMergedMap);
-    if (generatedFile.sources[0]?.inline) {
-      // The input source-map was inline so make the output one inline too.
+    const firstSource = generatedFile.sources[0];
+    if (firstSource && (firstSource.rawMap !== null || !sourceFile.isDeclarationFile) &&
+        firstSource.inline) {
+      // We render an inline source map if one of:
+      // * there was no input source map and this is not a typings file;
+      // * the input source map exists and was inline.
+      //
+      // We do not generate inline source maps for typings files unless there explicitly was one in
+      // the input file because these inline source maps can be very large and it impacts on the
+      // performance of IDEs that need to read them to provide intellisense etc.
       return [
         {path: generatedPath, contents: `${generatedFile.contents}\n${mergedMap.toComment()}`}
       ];

packages/compiler-cli/ngcc/test/rendering/dts_renderer_spec.ts

@@ -5,7 +5,9 @@
  * 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 {fromObject} from 'convert-source-map';
 import MagicString from 'magic-string';
+import {encode} from 'sourcemap-codec';
 import * as ts from 'typescript';
 
 import {absoluteFrom, getFileSystem} from '../../../src/ngtsc/file_system';
@@ -195,5 +197,47 @@ runInEachFileSystem(() => {
           result.find(f => f.path === _('/node_modules/test-package/typings/file.d.ts'))!;
       expect(typingsFile.contents).toContain(`\n// ADD MODUlE WITH PROVIDERS PARAMS\n`);
     });
+
+    it('should render an external source map for files whose original file does not have a source map',
+       () => {
+         const {
+           renderer,
+           decorationAnalyses,
+           privateDeclarationsAnalyses,
+           moduleWithProvidersAnalyses
+         } = createTestRenderer('test-package', [INPUT_PROGRAM], [INPUT_DTS_PROGRAM]);
+
+         const result = renderer.renderProgram(
+             decorationAnalyses, privateDeclarationsAnalyses, moduleWithProvidersAnalyses);
+
+         const typingsFile =
+             result.find(f => f.path === _('/node_modules/test-package/typings/file.d.ts'))!;
+         expect(typingsFile.contents).toContain('//# sourceMappingURL=file.d.ts.map');
+       });
+
+    it('should render an internal source map for files whose original file has an internal source map',
+       () => {
+         const sourceMap = fromObject({
+           'version': 3,
+           'file': 'file.d.ts',
+           'sources': ['file.d.ts'],
+           'names': [],
+           'mappings': encode([[]]),
+           'sourcesContent': [INPUT_DTS_PROGRAM.contents],
+         });
+         INPUT_DTS_PROGRAM.contents += sourceMap.toComment();
+         const {
+           renderer,
+           decorationAnalyses,
+           privateDeclarationsAnalyses,
+           moduleWithProvidersAnalyses
+         } = createTestRenderer('test-package', [INPUT_PROGRAM], [INPUT_DTS_PROGRAM]);
+         const result = renderer.renderProgram(
+             decorationAnalyses, privateDeclarationsAnalyses, moduleWithProvidersAnalyses);
+
+         const typingsFile =
+             result.find(f => f.path === _('/node_modules/test-package/typings/file.d.ts'))!;
+         expect(typingsFile.contents).toContain('//# sourceMappingURL=data:application/json');
+       });
   });
 });

packages/compiler-cli/ngcc/test/rendering/renderer_spec.ts

@@ -640,6 +640,24 @@ UndecoratedBase.ɵdir = ɵngcc0.ɵɵdefineDirective({ type: UndecoratedBase, vie
              expect(mapFile.path).toEqual(_('/node_modules/test-package/src/file.js.map'));
              expect(JSON.parse(mapFile.contents)).toEqual(MERGED_OUTPUT_PROGRAM_MAP.toObject());
            });
+
+
+        it('should render an internal source map for files whose original file does not have a source map',
+           () => {
+             const sourceFiles: TestFile[] = [JS_CONTENT];
+             const {
+               decorationAnalyses,
+               renderer,
+               switchMarkerAnalyses,
+               privateDeclarationsAnalyses
+             } = createTestRenderer('test-package', sourceFiles, undefined);
+             const [sourceFile, mapFile] = renderer.renderProgram(
+                 decorationAnalyses, switchMarkerAnalyses, privateDeclarationsAnalyses);
+             expect(sourceFile.path).toEqual(_('/node_modules/test-package/src/file.js'));
+             expect(sourceFile.contents)
+                 .toEqual(RENDERED_CONTENTS + '\n' + OUTPUT_PROGRAM_MAP.toComment());
+             expect(mapFile).toBeUndefined();
+           });
       });
 
       describe('@angular/core support', () => {