Fix minification of JSON files

Summary:
When moving the minification to the worker, I forgot to also minify JSON files (they have an early return).

This diff fixes this :)

Reviewed By: davidaurelio

Differential Revision: D7707317

fbshipit-source-id: 1114017b811861a6f2caebe79e1d79e6ad9a7b1e

packages/metro/src/JSTransformer/worker.js

@@ -33,10 +33,8 @@ const {
 import type {DynamicRequiresBehavior} from '../ModuleGraph/worker/collectDependencies';
 import type {LocalPath} from '../node-haste/lib/toLocalPath';
 import type {Ast} from '@babel/core';
-import type {BabelSourceMap} from '@babel/core';
 import type {Plugins as BabelPlugins} from 'babel-core';
 import type {LogEntry} from 'metro-core/src/Logger';
-import type {ResultWithMap} from 'metro-minify-uglify';
 import type {MetroSourceMapSegmentTuple} from 'metro-source-map';
 
 export type TransformedCode = {
@@ -153,15 +151,26 @@ async function transformCode(
     .digest('hex');
 
   if (filename.endsWith('.json')) {
-    const code = JsFileWrapping.wrapJson(sourceCode);
+    let code = JsFileWrapping.wrapJson(sourceCode);
+    let map = [];
 
     const transformFileEndLogEntry = getEndLogEntry(
       transformFileStartLogEntry,
       filename,
     );
 
+    if (options.minify) {
+      ({map, code} = await minifyCode(
+        filename,
+        code,
+        sourceCode,
+        map,
+        minifierPath,
+      ));
+    }
+
     return {
-      result: {dependencies: [], code, map: []},
+      result: {dependencies: [], code, map},
       sha1,
       transformFileStartLogEntry,
       transformFileEndLogEntry,
@@ -262,19 +271,13 @@ async function transformCode(
   let code = result.code;
 
   if (options.minify) {
-    const sourceMap = fromRawMappings([
+    ({map, code} = await minifyCode(
-      {code, source: sourceCode, map, path: filename},
-    ]).toMap(undefined, {});
-
-    const minified = await minifyCode(
       filename,
       result.code,
-      sourceMap,
+      sourceCode,
+      map,
       minifierPath,
-    );
+    ));
-
-    code = minified.code;
-    map = minified.map ? toBabelSegments(minified.map).map(toSegmentTuple) : [];
   }
 
   return {
@@ -285,15 +288,31 @@ async function transformCode(
   };
 }
 
-function minifyCode(
+async function minifyCode(
   filename: string,
   code: string,
-  sourceMap: BabelSourceMap,
+  source: string,
+  map: Array<MetroSourceMapSegmentTuple>,
   minifierPath: string,
-): ResultWithMap | Promise<ResultWithMap> {
+): Promise<{
+  code: string,
+  map: Array<MetroSourceMapSegmentTuple>,
+}> {
+  const sourceMap = fromRawMappings([
+    {code, source, map, path: filename},
+  ]).toMap(undefined, {});
+
   const minify = getMinifier(minifierPath);
+
   try {
-    return minify.withSourceMap(code, sourceMap, filename);
+    const minified = minify.withSourceMap(code, sourceMap, filename);
+
+    return {
+      code: minified.code,
+      map: minified.map
+        ? toBabelSegments(minified.map).map(toSegmentTuple)
+        : [],
+    };
   } catch (error) {
     if (error.constructor.name === 'JS_Parse_Error') {
       throw new Error(

packages/metro/src/JSTransformer/worker/__tests__/worker-test.js

@@ -252,4 +252,33 @@ describe('code transformation worker:', () => {
       ].join('\n'),
     );
   });
+
+  it('minifies a JSON file', async () => {
+    expect(
+      (await transformCode(
+        '/root/node_modules/bar/file.json',
+        `node_modules/bar/file.js`,
+        'arbitrary(code);',
+        path.join(__dirname, '../../../transformer.js'),
+        false,
+        {
+          dev: true,
+          minify: true,
+          transform: {},
+          enableBabelRCLookup: false,
+        },
+        [],
+        '',
+        'minifyModulePath',
+        'asyncRequire',
+        'throwAtRuntime',
+      )).result.code,
+    ).toBe(
+      [
+        '__d(function(global, require, module, exports) {',
+        '  module.exports = minified(code);;',
+        '});',
+      ].join('\n'),
+    );
+  });
 });