Breaking: Require decoded minifier source maps, remove unused source map APIs

docs/Configuration.md

@@ -549,6 +549,8 @@ Type: `string` (default: `'metro-minify-terser'`)
 
 Path, or package name resolvable from `metro-transform-worker`, to the minifier that minifies the code after transformation.
 
+The minifier is called with `{code, map, filename, reserved, config}`, where `map` is the source map of `code` and `config` is [`minifierConfig`](#minifierconfig). It returns, or resolves to, `{code, decodedMap}`, where `decodedMap` is the source map of the minified code, composed with `map`, in decoded form: `{mappings, names}`, with `mappings` as an array of segment arrays per line, as [`@jridgewell/sourcemap-codec`](https://github.com/jridgewell/sourcemaps/tree/main/packages/sourcemap-codec)'s `decode` returns them.
+
 #### `minifierConfig`
 
 Type: `{[key: string]: mixed}`

packages/metro-minify-terser/src/__tests__/minify-test.js

@@ -90,34 +90,17 @@ describe('Minification:', () => {
     expect(result.code).toBe(code);
   });
 
-  test('parses the source map object provided by terser and sets the sources property', async () => {
-    /* $FlowFixMe[incompatible-type](>=0.99.0 site=react_native_fb) This comment suppresses an
-     * error found when Flow v0.99 was deployed. To see the error, delete this
-     * comment and run Flow. */
-    terser.minify.mockResolvedValue({map: JSON.stringify(map), code: ''});
-    const result = await minify({...baseOptions, filename});
-    expect(result.map).toEqual({...map, sources: [filename]});
-  });
-
-  test('returns the decoded source map provided by terser, and encodes `map` only when read', async () => {
-    const decodedMap = {...map, mappings: [[[0, 0, 0, 0]]]};
-    let encodeCount = 0;
+  test('returns the decoded source map provided by terser', async () => {
     /* $FlowFixMe[incompatible-type] The mocked `minify` result isn't typed as
      * Terser's. */
     terser.minify.mockResolvedValue({
       code: '',
-      decoded_map: decodedMap,
-      // flowlint-next-line unsafe-getters-setters:off
-      get map() {
-        encodeCount++;
-        return JSON.stringify(map);
-      },
+      decoded_map: {...map, names: ['name0'], mappings: [[[0, 0, 0, 0, 0]]]},
     });
     const result = await minify({...baseOptions, filename});
-    expect(result.decodedMap).toEqual(decodedMap);
-    expect(encodeCount).toBe(0);
-    expect(result.map).toEqual({...map, sources: [filename]});
-    expect(result.map).toBe(result.map);
-    expect(encodeCount).toBe(1);
+    expect(result).toEqual({
+      code: '',
+      decodedMap: {names: ['name0'], mappings: [[[0, 0, 0, 0, 0]]]},
+    });
   });
 });

packages/metro-minify-terser/src/__tests__/terser-issue-1341-test.js

@@ -87,8 +87,9 @@ const GLO: MinifierOptions = {
 test('parallel calls do not clobber each other', async () => {
   const [barResult, gloResult] = await Promise.all([minify(BAR), minify(GLO)]);
 
-  const barMap = barResult.map;
-  const gloMap = gloResult.map;
+  const barMap = barResult.decodedMap;
+  const gloMap = gloResult.decodedMap;
 
+  expect(barMap).not.toBeNull();
   expect(gloMap).not.toEqual(barMap);
 });

packages/metro-minify-terser/src/minifier.js

@@ -9,7 +9,6 @@
  * @oncall react_native
  */
 
-import type {BabelDecodedMap, BasicSourceMap} from 'metro-source-map';
 import type {MinifierOptions, MinifierResult} from 'metro-transform-worker';
 
 import terser from 'terser';
@@ -18,32 +17,26 @@ export default async function minifier(
   options: MinifierOptions,
 ): Promise<MinifierResult> {
   const result = await minify(options);
-  const {getMap} = result;
-
-  if (!options.map || getMap == null) {
+  if (!options.map || result.decodedMap == null) {
     return {code: result.code};
   }
-
-  let map: ?BasicSourceMap;
-
-  return {
-    code: result.code,
-    // Terser encodes its map only when `result.map` is read.
-    // flowlint-next-line unsafe-getters-setters:off
-    get map(): BasicSourceMap {
-      if (map == null) {
-        map = {...JSON.parse(getMap()), sources: [options.filename]};
-      }
-      return map;
-    },
-    decodedMap: result.decodedMap,
-  };
+  const {mappings, names} = result.decodedMap;
+  return {code: result.code, decodedMap: {mappings, names}};
 }
 
 async function minify({code, map, reserved, config}: MinifierOptions): Promise<{
   code: string,
-  getMap: ?() => string,
-  decodedMap: ?BabelDecodedMap,
+  decodedMap: ?{
+    mappings: Array<
+      Array<
+        | [number]
+        | [number, number, number, number]
+        | [number, number, number, number, number],
+      >,
+    >,
+    names: Array<string>,
+    ...
+  },
 }> {
   const options = {
     ...config,
@@ -76,7 +69,6 @@ async function minify({code, map, reserved, config}: MinifierOptions): Promise<{
 
   return {
     code: result.code,
-    getMap: options.sourceMap ? () => result.map : null,
     decodedMap: result.decoded_map,
   };
 }

packages/metro-source-map/API.md

@@ -125,15 +125,6 @@ export interface SourceMapGenerator {
   toString(file?: string, options?: {excludeSource?: boolean | undefined}): string;
 }
 
-// @deprecated
-export function toBabelSegments(sourceMap: BasicSourceMap): Array<BabelSourceMapSegment>;
-
-// @deprecated
-export function toSegmentTuple(mapping: BabelSourceMapSegment): MetroSourceMapSegmentTuple;
-
-// @deprecated
-export function tuplesFromBabelDecodedMap(decodedMap: BabelDecodedMap): Array<MetroSourceMapSegmentTuple>;
-
 export type VlqMap = {
   readonly mappings: string;
   readonly names: ReadonlyArray<string>;

packages/metro-source-map/package.json

@@ -20,6 +20,7 @@
   "dependencies": {
     "@babel/traverse": "^7.29.0",
     "@babel/types": "^7.29.8",
+    "@jridgewell/sourcemap-codec": "^1.5.0",
     "flow-enums-runtime": "^0.0.6",
     "invariant": "^2.2.4",
     "metro-symbolicate": "0.87.1",