Use git diff instead of diff package. Too much dependencies for a sim…

…ple task.

src/seed_tools/commands/check_study.ts

@@ -4,10 +4,10 @@
 // You can obtain one at https://mozilla.org/MPL/2.0/.
 
 import { Command } from '@commander-js/extra-typings';
-import * as diff from 'diff';
 import { promises as fs } from 'fs';
 import DefaultMap from 'src/base/containers/default_map';
 import { type Study } from '../../proto/generated/study';
+import diffStrings from '../utils/diff_strings';
 import * as study_json_utils from '../utils/study_json_utils';
 import * as study_validation from '../utils/study_validation';
 
@@ -76,12 +76,12 @@ async function checkAndOptionallyFixFormat(
     } else {
       errors.push(
         `Format required:\n` +
-          diff.createTwoFilesPatch(
-            studyFilePath,
-            studyFilePath + '.formatted',
+          (await diffStrings(
             studyArrayString,
             stringifiedStudyArray,
-          ),
+            studyFilePath,
+            studyFilePath + '.formatted',
+          )),
       );
     }
   }

src/seed_tools/commands/compare_seeds.ts

@@ -4,19 +4,19 @@
 // You can obtain one at https://mozilla.org/MPL/2.0/.
 
 import { Command } from '@commander-js/extra-typings';
-import * as diff from 'diff';
 import { promises as fs } from 'fs';
 import { VariationsSeed } from '../../proto/generated/variations_seed';
+import diffStrings from '../utils/diff_strings';
 
 export default new Command('compare_seeds')
   .description('Compare two seed.bin')
   .argument('<seed1_file>', 'seed1 file')
   .argument('<seed2_file>', 'seed2 file')
   .action(main);
 
-async function main(seed1File: string, seed2File: string) {
-  const seed1Binary: Buffer = await fs.readFile(seed1File);
-  const seed2Binary: Buffer = await fs.readFile(seed2File);
+async function main(seed1FilePath: string, seed2FilePath: string) {
+  const seed1Binary: Buffer = await fs.readFile(seed1FilePath);
+  const seed2Binary: Buffer = await fs.readFile(seed2FilePath);
   if (seed1Binary.equals(seed2Binary)) {
     console.log('Seeds are equal');
     process.exit(0);
@@ -43,11 +43,11 @@ async function main(seed1File: string, seed2File: string) {
   if (seed1JsonString !== seed2JsonString) {
     console.error('Seeds are different');
     console.error(
-      diff.createTwoFilesPatch(
-        seed1File,
-        seed2File,
+      await diffStrings(
         seed1JsonString,
         seed2JsonString,
+        seed1FilePath,
+        seed2FilePath,
       ),
     );
   } else {

src/seed_tools/utils/diff_strings.test.ts

@@ -0,0 +1,25 @@
+// Copyright (c) 2024 The Brave Authors. All rights reserved.
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+import diffStrings from './diff_strings';
+
+describe('diffStrings', () => {
+  it('should return the diff between two strings', async () => {
+    const string1 = 'Hello, world!';
+    const string2 = 'Hello, brave!';
+    const displayFileName1 = 'file1.txt';
+    const displayFileName2 = 'file2.txt';
+
+    const result = await diffStrings(
+      string1,
+      string2,
+      displayFileName1,
+      displayFileName2,
+    );
+
+    expect(result).toContain('-Hello, world!');
+    expect(result).toContain('+Hello, brave!');
+  });
+});

src/seed_tools/utils/diff_strings.ts

@@ -0,0 +1,56 @@
+// Copyright (c) 2024 The Brave Authors. All rights reserved.
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+import { exec } from 'child_process';
+import fs from 'fs/promises';
+import os from 'os';
+import path from 'path';
+
+export default async function diffStrings(
+  string1: string,
+  string2: string,
+  displayFileName1: string,
+  displayFileName2: string,
+): Promise<string> {
+  const tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), 'diffString-'));
+
+  const tmpFile1 = path
+    .join(tmpDir, `file1-${Date.now()}.txt`)
+    .replaceAll('\\', '/');
+  const tmpFile2 = path
+    .join(tmpDir, `file2-${Date.now()}.txt`)
+    .replaceAll('\\', '/');
+
+  // Write strings to temporary files.
+  await fs.writeFile(tmpFile1, string1);
+  await fs.writeFile(tmpFile2, string2);
+
+  return await new Promise<string>((resolve, reject) => {
+    // Use git diff to generate readable diff.
+    exec(
+      `git diff --no-index --src-prefix= --dst-prefix= -- ${tmpFile1} ${tmpFile2}`,
+      { encoding: 'utf8' },
+      (error, stdout, stderr) => {
+        if (error !== null && error.code !== 1) {
+          // git diff returns 1 if there are differences
+          reject(new Error(stderr));
+          return;
+        }
+
+        const result = stdout
+          .replaceAll(tmpFile1, displayFileName1)
+          .replaceAll(tmpFile2, displayFileName2);
+
+        resolve(result);
+      },
+    );
+  }).finally(() => {
+    // eslint-disable-next-line @typescript-eslint/no-floating-promises
+    (async () => {
+      // Clean up temporary directory.
+      await fs.rm(tmpDir, { recursive: true });
+    })();
+  });
+}

src/test/data/unformatted_studies/test1/expected_output.txt

@@ -1,5 +1,4 @@
-@@ -6,9 +6,9 @@
-         "name": "Enabled",
+@@ -7,7 +7,7 @@
          "probability_weight": 100,
          "feature_association": {
            "enable_feature": [
@@ -8,9 +7,7 @@
            ]
          }
        },
-       {
-@@ -20,21 +20,21 @@
-           ]
+@@ -21,19 +21,19 @@
          }
        },
        {
@@ -34,4 +31,3 @@
          "PLATFORM_MAC",
          "PLATFORM_LINUX",
          "PLATFORM_ANDROID"
-       ]