Merge pull request #97 from ampproject/return-decoded-mapping

Allow returning SourceMap with decoded mappings

src/remapping.ts

@@ -17,7 +17,7 @@
 import buildSourceMapTree from './build-source-map-tree';
 import SourceMap from './source-map';
 
-import type { SourceMapInput, SourceMapLoader } from './types';
+import type { SourceMapInput, SourceMapLoader, Options } from './types';
 
 /**
  * Traces through all the mappings in the root sourcemap, through the sources
@@ -28,14 +28,19 @@ import type { SourceMapInput, SourceMapLoader } from './types';
  * it returns a falsey value, that source file is treated as an original,
  * unmodified source file.
  *
- * Pass `excludeContent` content to exclude any self-containing source file
- * content from the output sourcemap.
+ * Pass `excludeContent` to exclude any self-containing source file content
+ * from the output sourcemap.
+ *
+ * Pass `decodedMappings` to receive a SourceMap with decoded (instead of
+ * VLQ encoded) mappings.
  */
 export default function remapping(
   input: SourceMapInput | SourceMapInput[],
   loader: SourceMapLoader,
-  excludeContent?: boolean
+  options?: boolean | Options
 ): SourceMap {
+  const opts =
+    typeof options === 'object' ? options : { excludeContent: !!options, decodedMappings: false };
   const graph = buildSourceMapTree(input, loader);
-  return new SourceMap(graph.traceMappings(), !!excludeContent);
+  return new SourceMap(graph.traceMappings(), opts);
 }

src/source-map.ts

@@ -16,33 +16,35 @@
 
 import { encode } from 'sourcemap-codec';
 
-import type { DecodedSourceMap, RawSourceMap } from './types';
+import type { DecodedSourceMap, RawSourceMap, Options } from './types';
 
 /**
  * A SourceMap v3 compatible sourcemap, which only includes fields that were
  * provided to it.
  */
-export default class SourceMap implements RawSourceMap {
+export default class SourceMap implements SourceMap {
   file?: string | null;
-  mappings: string;
+  mappings: RawSourceMap['mappings'] | DecodedSourceMap['mappings'];
   sourceRoot?: string;
   names: string[];
   sources: (string | null)[];
   sourcesContent?: (string | null)[];
   version: 3;
 
-  constructor(map: DecodedSourceMap, excludeContent: boolean) {
+  constructor(map: DecodedSourceMap, options: Options) {
     this.version = 3; // SourceMap spec says this should be first.
     if ('file' in map) this.file = map.file;
-    this.mappings = encode(map.mappings);
+    this.mappings = options.decodedMappings ? map.mappings : encode(map.mappings);
     this.names = map.names;
 
     // TODO: We first need to make all source URIs relative to the sourceRoot
     // before we can support a sourceRoot.
     // if ('sourceRoot' in map) this.sourceRoot = map.sourceRoot;
 
     this.sources = map.sources;
-    if (!excludeContent && 'sourcesContent' in map) this.sourcesContent = map.sourcesContent;
+    if (!options.excludeContent && 'sourcesContent' in map) {
+      this.sourcesContent = map.sourcesContent;
+    }
   }
 
   toString(): string {

src/types.ts

@@ -55,3 +55,8 @@ export interface SourceMapSegmentObject {
 export type SourceMapInput = string | RawSourceMap | DecodedSourceMap;
 
 export type SourceMapLoader = (file: string) => SourceMapInput | null | undefined;
+
+export type Options = {
+  excludeContent: boolean;
+  decodedMappings: boolean;
+};

test/unit/source-map.ts

@@ -24,50 +24,60 @@ describe('SourceMap', () => {
     sources: ['file.js'],
     version: 3,
   };
+  const opts = {
+    excludeContent: false,
+    decodedMappings: false,
+  };
 
   test('it is a compliant, v3 sourcemap', () => {
-    const map = new SourceMap(decoded, false);
+    const map = new SourceMap(decoded, opts);
     expect(map).toHaveProperty('mappings', 'AAAA');
     expect(map).toHaveProperty('names', decoded.names);
     expect(map).toHaveProperty('sources', decoded.sources);
     expect(map).toHaveProperty('version', 3);
   });
 
   test('it does not include properties missing from input', () => {
-    const map = new SourceMap(decoded, false);
+    const map = new SourceMap(decoded, opts);
     expect(map).not.toHaveProperty('file');
     expect(map).not.toHaveProperty('sourceRoot');
     expect(map).not.toHaveProperty('sourcesContent');
   });
 
   test('it can include a file', () => {
     const file = 'foobar.js';
-    const map = new SourceMap({ ...decoded, file }, false);
+    const map = new SourceMap({ ...decoded, file }, opts);
     expect(map).toHaveProperty('file', file);
   });
 
   // TODO: support sourceRoot
   test.skip('it can include a sourceRoot', () => {
     const sourceRoot = 'https://foo.com/';
-    const map = new SourceMap({ ...decoded, sourceRoot }, false);
+    const map = new SourceMap({ ...decoded, sourceRoot }, opts);
     expect(map).toHaveProperty('sourceRoot', sourceRoot);
   });
 
   test('it can include a sourcesContent', () => {
     const sourcesContent = ['1 + 1'];
-    const map = new SourceMap({ ...decoded, sourcesContent }, false);
+    const map = new SourceMap({ ...decoded, sourcesContent }, opts);
     expect(map).toHaveProperty('sourcesContent', sourcesContent);
   });
 
   test('sourcesContent can be manually excluded', () => {
     const sourcesContent = ['1 + 1'];
-    const map = new SourceMap({ ...decoded, sourcesContent }, true);
+    const map = new SourceMap({ ...decoded, sourcesContent }, { ...opts, excludeContent: true });
     expect(map).not.toHaveProperty('sourcesContent');
   });
 
+  test('mappings can be decoded', () => {
+    const sourcesContent = ['1 + 1'];
+    const map = new SourceMap({ ...decoded, sourcesContent }, { ...opts, decodedMappings: true });
+    expect(map).toHaveProperty('mappings', [[[0, 0, 0, 0]]]);
+  });
+
   describe('toString()', () => {
     test('returns the sourcemap in JSON', () => {
-      const map = new SourceMap(decoded, false);
+      const map = new SourceMap(decoded, opts);
       expect(JSON.parse(map.toString())).toEqual(map);
     });
   });