fix saveCells

lib/GoogleSpreadsheetCell.js

@@ -177,11 +177,18 @@ class GoogleSpreadsheetCell {
   // used by worksheet when saving cells
   // returns an individual batchUpdate request to update the cell
   _getUpdateRequest() {
+    // this logic should match the _isDirty logic above
+    // but we need it broken up to build the request below
     const isValueUpdated = this._draftData.value !== undefined;
     const isNoteUpdated = this._draftData.note !== undefined;
     const isFormatUpdated = _.keys(this._draftData.userEnteredFormat || {}).length;
     const isFormatCleared = this._draftData.clearFormat;
 
+    // if no updates, we return null, which we can filter out later before sending requests
+    if (!_.some([isValueUpdated, isNoteUpdated, isFormatUpdated, isFormatCleared])) {
+      return null;
+    }
+
     return {
       updateCells: {
         rows: [{

lib/GoogleSpreadsheetWorksheet.js

@@ -216,6 +216,13 @@ class GoogleSpreadsheetWorksheet {
     // and we dont want to accidentally overwrite something
     const requests = _.map(cellsToUpdate, (cell) => cell._getUpdateRequest());
     const responseRanges = _.map(cellsToUpdate, (c) => `${this.a1SheetName}!${c.a1Address}`);
+
+    // if nothing is being updated the request returned is just `null`
+    // so we make sure at least 1 request is valid - otherwise google throws a 400
+    if (!_.compact(requests).length) {
+      throw new Error('At least one cell must have something to update');
+    }
+
     await this._spreadsheet._makeBatchUpdateRequest(requests, responseRanges);
   }
 

test/cells.test.js

@@ -164,6 +164,22 @@ describe('Cell-based operations', () => {
       expect(() => { c1.value = { foo: 1 }; }).toThrow();
     });
 
+    describe('calling saveCells directly', () => {
+      it('can save an array of cells', async () => {
+        _.each([c1, c2, c3], (cell) => { cell.value = 'calling saveCells'; });
+        await sheet.saveCells([c1, c2, c3]);
+      });
+
+      it('can save a mix of dirty and non-dirty', async () => {
+        c2.value = 'saveCells again';
+        await sheet.saveCells([c1, c2, c3]);
+      });
+
+      it('will throw an error if no cells are dirty', async () => {
+        await expect(sheet.saveCells([c1, c2, c3])).rejects.toThrow();
+      });
+    });
+
     describe('cell formulas', () => {
       it('can update a cell with a formula via .value', async () => {
         c1.value = '=2';