Multiple requests to the Delta Bundler when there is an error should produce an Error

Reviewed By: jeanlauliac

Differential Revision: D5814215

fbshipit-source-id: 9a72057078819d07ddbd5d4f949d7bdf13aff29e

packages/metro-bundler/src/DeltaBundler/DeltaCalculator.js

@@ -103,6 +103,14 @@ class DeltaCalculator extends EventEmitter {
 
     try {
       result = await this._currentBuildPromise;
+    } catch (error) {
+      // In case of error, we don't want to mark the modified files as
+      // processed (since we haven't actually created any delta). If we do not
+      // do so, asking for a delta after an error will produce an empty Delta,
+      // which is not correct.
+      modifiedFiles.forEach(file => this._modifiedFiles.add(file));
+
+      throw error;
     } finally {
       this._currentBuildPromise = null;
     }

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

@@ -234,4 +234,19 @@ describe('DeltaCalculator', () => {
 
     expect(onChangeFile.mock.calls.length).toBe(0);
   });
+
+  it('should retry to build the last delta after getting an error', async () => {
+    await deltaCalculator.getDelta();
+
+    fileWatcher.emit('change', {eventsQueue: [{filePath: '/foo'}]});
+
+    Bundler.prototype.getShallowDependencies.mockImplementation(async () => {
+      throw new Error('error');
+    });
+
+    await expect(deltaCalculator.getDelta()).rejects.toBeInstanceOf(Error);
+
+    // This second time it should still throw an error.
+    await expect(deltaCalculator.getDelta()).rejects.toBeInstanceOf(Error);
+  });
 });