Do not do unnecessary work when re-adding a file after deleting it

Reviewed By: mjesun

Differential Revision: D7009760

fbshipit-source-id: 18a93443226bdec4decb69f75539e27f528c128c

packages/metro/src/DeltaBundler/DeltaCalculator.js

@@ -220,6 +220,7 @@ class DeltaCalculator extends EventEmitter {
       this._deletedFiles.add(filePath);
       this._modifiedFiles.delete(filePath);
     } else {
+      this._deletedFiles.delete(filePath);
       this._modifiedFiles.add(filePath);
     }
 

packages/metro/src/DeltaBundler/__tests__/DeltaCalculator-test.js

@@ -313,6 +313,30 @@ describe('DeltaCalculator', () => {
     expect(traverseDependencies.mock.calls[0][0]).toEqual(['/bundle']);
   });
 
+  it('should not do unnecessary work when adding a file after deleting it', async () => {
+    await deltaCalculator.getDelta();
+
+    // First delete a file
+    fileWatcher.emit('change', {
+      eventsQueue: [{type: 'delete', filePath: '/foo'}],
+    });
+
+    // Then add it again
+    fileWatcher.emit('change', {eventsQueue: [{filePath: '/foo'}]});
+
+    traverseDependencies.mockReturnValue(
+      Promise.resolve({
+        added: new Map([['/foo', edgeModule]]),
+        deleted: new Set(),
+      }),
+    );
+
+    await deltaCalculator.getDelta();
+
+    expect(traverseDependencies).toHaveBeenCalledTimes(1);
+    expect(traverseDependencies.mock.calls[0][0]).toEqual(['/foo']);
+  });
+
   describe('getTransformerOptions()', () => {
     it('should calculate the transform options correctly', async () => {
       expect(await deltaCalculator.getTransformerOptions()).toEqual({

packages/metro/src/DeltaBundler/__tests__/traverseDependencies-test.js

@@ -221,28 +221,6 @@ describe('edge cases', () => {
     });
   });
 
-  it('modify a file and delete it afterwards', async () => {
-    const edges = new Map();
-    await initialTraverseDependencies('/bundle', dependencyGraph, {}, edges);
-
-    mockedDependencyTree.set(moduleFoo.path, [moduleBar]);
-
-    // Modify /baz, rename it to /qux and modify it again.
-    expect(
-      getPaths(
-        await traverseDependencies(
-          ['/baz', '/foo'],
-          dependencyGraph,
-          {},
-          edges,
-        ),
-      ),
-    ).toEqual({
-      added: new Set(['/foo']),
-      deleted: new Set(['/baz']),
-    });
-  });
-
   it('move a file to a different folder', async () => {
     const edges = new Map();
     await initialTraverseDependencies('/bundle', dependencyGraph, {}, edges);