From 5c8456aaa66e433285a54021a182d8f59eb4f1e8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rub=C3=A9n=20Norte?= <rubennorte@fb.com>
Date: Mon, 17 Sep 2018 14:25:49 +0100
Subject: [PATCH] Preserve file data when sha1s match

---
 .../src/crawlers/__tests__/watchman.test.js   | 22 +++++++++++-------
 .../jest-haste-map/src/crawlers/watchman.js   | 23 ++++++++++++++-----
 2 files changed, 31 insertions(+), 14 deletions(-)

diff --git a/packages/jest-haste-map/src/crawlers/__tests__/watchman.test.js b/packages/jest-haste-map/src/crawlers/__tests__/watchman.test.js
index ebb9574e0974..071acb2fcd32 100644
--- a/packages/jest-haste-map/src/crawlers/__tests__/watchman.test.js
+++ b/packages/jest-haste-map/src/crawlers/__tests__/watchman.test.js
@@ -223,6 +223,8 @@ describe('watchman watch', () => {
   });
 
   test('resets the file object when watchman is restarted', () => {
+    const mockTomatoSha1 = '321f6b7e8bf7f29aab89c5e41a555b1b0baa41a9';
+
     mockResponse = {
       'list-capabilities': {
         [undefined]: {
@@ -244,8 +246,9 @@ describe('watchman watch', () => {
               name: 'fruits/banana.js',
             },
             {
+              'content.sha1hex': mockTomatoSha1,
               exists: true,
-              mtime_ms: {toNumber: () => 31},
+              mtime_ms: {toNumber: () => 76},
               name: 'fruits/tomato.js',
             },
           ],
@@ -256,8 +259,10 @@ describe('watchman watch', () => {
       'watch-project': WATCH_PROJECT_MOCK,
     };
 
-    const mockMetadata = ['Banana', 41, 1, ['Raspberry'], null];
-    mockFiles.set(BANANA, mockMetadata);
+    const mockBananaMetadata = ['Banana', 41, 1, ['Raspberry'], null];
+    mockFiles.set(BANANA, mockBananaMetadata);
+    const mockTomatoMetadata = ['Tomato', 31, 1, [], mockTomatoSha1];
+    mockFiles.set(TOMATO, mockTomatoMetadata);
 
     const clocks = createMap({
       [ROOT_MOCK]: 'c:fake-clock:1',
@@ -284,17 +289,18 @@ describe('watchman watch', () => {
       // /fruits/strawberry.js was removed from the file list.
       expect(data.files).toEqual(
         createMap({
-          [BANANA]: mockMetadata,
+          [BANANA]: mockBananaMetadata,
           [KIWI]: ['', 42, 0, [], null],
-          [TOMATO]: mockFiles.get(TOMATO),
+          [TOMATO]: ['Tomato', 76, 1, [], mockTomatoSha1],
         }),
       );
 
       // Even though the file list was reset, old file objects are still reused
-      // if no changes have been made.
-      expect(data.files.get(BANANA)).toBe(mockMetadata);
+      // if no changes have been made
+      expect(data.files.get(BANANA)).toBe(mockBananaMetadata);
 
-      expect(data.files.get(TOMATO)).toBe(mockFiles.get(TOMATO));
+      // Old file objects are not reused if they have a different mtime
+      expect(data.files.get(TOMATO)).not.toBe(mockTomatoMetadata);
     });
   });
 
diff --git a/packages/jest-haste-map/src/crawlers/watchman.js b/packages/jest-haste-map/src/crawlers/watchman.js
index 684d6eeb55e1..cc7a9dfa6f47 100644
--- a/packages/jest-haste-map/src/crawlers/watchman.js
+++ b/packages/jest-haste-map/src/crawlers/watchman.js
@@ -169,16 +169,27 @@ module.exports = async function watchmanCrawl(
           typeof fileData.mtime_ms === 'number'
             ? fileData.mtime_ms
             : fileData.mtime_ms.toNumber();
+        let sha1hex = fileData['content.sha1hex'];
+        if (typeof sha1hex !== 'string' || sha1hex.length !== 40) {
+          sha1hex = null;
+        }
+
         const existingFileData = data.files.get(name);
         if (existingFileData && existingFileData[H.MTIME] === mtime) {
           files.set(name, existingFileData);
+        } else if (
+          existingFileData &&
+          sha1hex &&
+          existingFileData[H.SHA1] === sha1hex
+        ) {
+          files.set(name, [
+            existingFileData[0],
+            mtime,
+            existingFileData[2],
+            existingFileData[3],
+            existingFileData[4],
+          ]);
         } else {
-          let sha1hex = fileData['content.sha1hex'];
-
-          if (typeof sha1hex !== 'string' || sha1hex.length !== 40) {
-            sha1hex = null;
-          }
-
           // See ../constants.js
           files.set(name, ['', mtime, 0, [], sha1hex]);
         }