If parent item is missing remotely, mark as unsynced and add to queue

This shouldn't happen, but there've been some reports of it.

chrome/content/zotero/xpcom/sync/syncEngine.js

@@ -1113,6 +1113,32 @@ Zotero.Sync.Data.Engine.prototype._uploadObjects = Zotero.Promise.coroutine(func
 				Zotero.logError("Error for " + objectType + " " + jsonBatch[index].key + " in "
 					+ this.library.name + ":\n\n" + e);
 				
+				// If parent item is missing remotely and it isn't in the queue (which shouldn't happen),
+				// mark it as unsynced and add to queue
+				if (e.code == 400 && objectType == 'item' && data && data.parentItem) {
+					let parentItem = Zotero.Items.getByLibraryAndKey(this.libraryID, data.parentItem);
+					if (!parentItem) {
+						throw new Error(`Item ${this.libraryID}/${jsonBatch[index].key} references parent `
+							+ `item ${data.parentItem}, which doesn't exist`);
+					}
+					
+					let id = parentItem.id;
+					// If parent item isn't already in queue, mark it as unsynced and add it
+					if (!queue.find(o => o.id == id) && !batch.find(o => o.id == id)) {
+						yield Zotero.Sync.Data.Local.markObjectAsUnsynced(parentItem);
+						Zotero.logError(`Adding parent item ${data.parentItem} to upload queue`);
+						queue.push({
+							id,
+							json: null,
+							tries: 0,
+							failed: false
+						});
+						// Pretend that we were successful so syncing continues
+						numSuccessful++;
+						continue;
+					}
+				}
+				
 				// This shouldn't happen, because the upload request includes a library version and should
 				// prevent an outdated upload before the object version is checked. If it does, we need to
 				// do a full sync. This error is checked in handleUploadError().

test/tests/syncEngineTest.js

@@ -2175,6 +2175,75 @@ describe("Zotero.Sync.Data.Engine", function () {
 			var result = yield engine._startUpload();
 			assert.equal(result, engine.UPLOAD_RESULT_OBJECT_CONFLICT);
 		});
+		
+		
+		it("should mark local parent item as unsynced if it doesn't exist when uploading child", function* () {
+			({ engine, client, caller } = yield setup());
+			
+			var library = Zotero.Libraries.userLibrary;
+			var libraryID = library.id;
+			var lastLibraryVersion = 5;
+			library.libraryVersion = lastLibraryVersion;
+			yield library.saveTx();
+			
+			var item = createUnsavedDataObject('item');
+			// Set the parent item as synced (though this shouldn't happen)
+			item.synced = true;
+			yield item.saveTx();
+			var note = yield createDataObject('item', { itemType: 'note', parentID: item.id });
+			
+			var called = 0;
+			server.respond(function (req) {
+				let requestJSON = JSON.parse(req.requestBody);
+				
+				if (called == 0) {
+					assert.lengthOf(requestJSON, 1);
+					assert.equal(requestJSON[0].key, note.key);
+					req.respond(
+						200,
+						{
+							"Last-Modified-Version": lastLibraryVersion
+						},
+						JSON.stringify({
+							successful: {},
+							unchanged: {},
+							failed: {
+								0: {
+									code: 400,
+									message: `Parent item '${item.key}' doesn't exist`,
+									data: {
+										parentItem: item.key
+									}
+								}
+							}
+						})
+					);
+				}
+				else if (called == 1) {
+					assert.lengthOf(requestJSON, 2);
+					assert.sameMembers(requestJSON.map(o => o.key), [item.key, note.key]);
+					req.respond(
+						200,
+						{
+							"Last-Modified-Version": ++lastLibraryVersion
+						},
+						JSON.stringify({
+							successful: {
+								0: item.toResponseJSON(),
+								1: note.toResponseJSON()
+							},
+							unchanged: {},
+							failed: {}
+						})
+					);
+				}
+				called++;
+			});
+			
+			var result = yield engine._startUpload();
+			assert.equal(result, engine.UPLOAD_RESULT_SUCCESS);
+			assert.equal(called, 2);
+		});
 	});