editor: use file system api for save as

This makes use of the new web file system api for a better user
experience when saving a file. It now shows a proper save as dialog
instead of just downloading the file automatically.

Fixes: https://github.com/pybricks/support/issues/84

src/editor/actions.ts

@@ -5,25 +5,19 @@ import { monaco } from 'react-monaco-editor';
 import { Action } from 'redux';
 
 export enum EditorActionType {
-    /**
-     * The current (active) editor changed.
-     */
+    /** The current (active) editor changed. */
     Current = 'editor.action.current',
-    /**
-     * Save the current file to disk.
-     */
+    /** Save the current file to disk. */
     SaveAs = 'editor.action.saveAs',
-    /**
-     * Open a file.
-     */
+    /** Saving the file succeeded. */
+    DidSaveAs = 'editor.action.didSaveAs',
+    /** Saving the file failed. */
+    DidFailToSaveAs = 'editor.action.didFailToSaveAs',
+    /** Open a file. */
     Open = 'editor.action.open',
-    /**
-     * Storage was changed outside of the app.
-     */
+    /** Storage was changed outside of the app. */
     StorageChanged = 'editor.action.storageChanged',
-    /**
-     * Reload program from local storage.
-     */
+    /** Reload program from local storage. */
     ReloadProgram = 'editor.action.reloadProgram',
 }
 
@@ -53,6 +47,24 @@ export function saveAs(): EditorSaveAsAction {
     return { type: EditorActionType.SaveAs };
 }
 
+/** Action that indicates saving a file succeeded. */
+export type EditorDidSaveAsAction = Action<EditorActionType.DidSaveAs>;
+
+/** Action that indicates saving a file succeeded. */
+export function didSaveAs(): EditorDidSaveAsAction {
+    return { type: EditorActionType.DidSaveAs };
+}
+
+/** Action that indicates saving a file failed. */
+export type EditorDidFailToSaveAsAction = Action<EditorActionType.DidFailToSaveAs> & {
+    err: Error;
+};
+
+/** Action that indicates saving a file failed. */
+export function didFailToSaveAs(err: Error): EditorDidFailToSaveAsAction {
+    return { type: EditorActionType.DidFailToSaveAs, err };
+}
+
 /**
  * Action that opens a file.
  */
@@ -97,5 +109,7 @@ export type EditorAction =
     | CurrentEditorAction
     | EditorOpenAction
     | EditorSaveAsAction
+    | EditorDidSaveAsAction
+    | EditorDidFailToSaveAsAction
     | EditorStorageChangedAction
     | EditorReloadProgramAction;

src/editor/sagas.test.ts

@@ -1,10 +1,11 @@
 // SPDX-License-Identifier: MIT
 // Copyright (c) 2020-2021 The Pybricks Authors
 
+import FileSaver from 'file-saver';
 import { mock } from 'jest-mock-extended';
 import { monaco } from 'react-monaco-editor';
 import { AsyncSaga } from '../../test';
-import { open, reloadProgram, saveAs } from './actions';
+import { didFailToSaveAs, didSaveAs, open, reloadProgram, saveAs } from './actions';
 import editor from './sagas';
 
 jest.mock('react-monaco-editor');
@@ -22,15 +23,105 @@ test('open', async () => {
     await saga.end();
 });
 
-test('saveAs', async () => {
-    const mockEditor = mock<monaco.editor.ICodeEditor>();
-    const saga = new AsyncSaga(editor, { editor: { current: mockEditor } });
+describe('saveAs', () => {
+    test('web file system api can succeed', async () => {
+        const mockEditor = mock<monaco.editor.ICodeEditor>();
+        const saga = new AsyncSaga(editor, { editor: { current: mockEditor } });
 
-    saga.put(saveAs());
+        // window.showSaveFilePicker is not defined in the test environment
+        // so we can't use spyOn().
+        const mockWriteable = mock<FileSystemWritableFileStream>();
+        const originalShowSaveFilePicker = window.showSaveFilePicker;
+        window.showSaveFilePicker = jest.fn().mockResolvedValue(
+            mock<FileSystemFileHandle>({
+                createWritable: jest.fn().mockResolvedValue(mockWriteable),
+            }),
+        );
 
-    expect(mockEditor.getValue).toBeCalled();
+        saga.put(saveAs());
 
-    await saga.end();
+        expect(mockEditor.getValue).toHaveBeenCalled();
+
+        const action = await saga.take();
+        expect(action).toEqual(didSaveAs());
+        expect(window.showSaveFilePicker).toHaveBeenCalled();
+        expect(mockWriteable.write).toHaveBeenCalled();
+        expect(mockWriteable.close).toHaveBeenCalled();
+
+        await saga.end();
+
+        window.showSaveFilePicker = originalShowSaveFilePicker;
+    });
+
+    test('web file system api can fail', async () => {
+        const mockEditor = mock<monaco.editor.ICodeEditor>();
+        const saga = new AsyncSaga(editor, { editor: { current: mockEditor } });
+
+        // window.showSaveFilePicker is not defined in the test environment
+        // so we can't use spyOn().
+        const testError = new Error('test error');
+        const originalShowSaveFilePicker = window.showSaveFilePicker;
+        window.showSaveFilePicker = jest.fn().mockResolvedValue(
+            mock<FileSystemFileHandle>({
+                createWritable: jest.fn().mockRejectedValue(testError),
+            }),
+        );
+
+        saga.put(saveAs());
+
+        expect(mockEditor.getValue).toHaveBeenCalled();
+
+        const action = await saga.take();
+        expect(action).toEqual(didFailToSaveAs(testError));
+        expect(window.showSaveFilePicker).toHaveBeenCalled();
+
+        await saga.end();
+
+        window.showSaveFilePicker = originalShowSaveFilePicker;
+    });
+
+    test('fallback can succeed', async () => {
+        const mockEditor = mock<monaco.editor.ICodeEditor>();
+        const saga = new AsyncSaga(editor, { editor: { current: mockEditor } });
+
+        const mockFileSaverSaveAs = jest.spyOn(FileSaver, 'saveAs');
+
+        saga.put(saveAs());
+
+        expect(mockEditor.getValue).toHaveBeenCalled();
+
+        const action = await saga.take();
+        expect(action).toEqual(didSaveAs());
+        expect(mockFileSaverSaveAs).toHaveBeenCalled();
+
+        await saga.end();
+
+        mockFileSaverSaveAs.mockRestore();
+    });
+
+    test('fallback can fail', async () => {
+        const mockEditor = mock<monaco.editor.ICodeEditor>();
+        const saga = new AsyncSaga(editor, { editor: { current: mockEditor } });
+
+        const testError = new Error('test error');
+        const mockFileSaverSaveAs = jest
+            .spyOn(FileSaver, 'saveAs')
+            .mockImplementation(() => {
+                throw testError;
+            });
+
+        saga.put(saveAs());
+
+        expect(mockEditor.getValue).toHaveBeenCalled();
+
+        const action = await saga.take();
+        expect(action).toEqual(didFailToSaveAs(testError));
+        expect(mockFileSaverSaveAs).toHaveBeenCalled();
+
+        await saga.end();
+
+        mockFileSaverSaveAs.mockRestore();
+    });
 });
 
 test('reloadProgram', async () => {

src/editor/sagas.ts

@@ -1,14 +1,17 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2020 The Pybricks Authors
+// Copyright (c) 2020-2021 The Pybricks Authors
 
 import FileSaver from 'file-saver';
-import { select, takeEvery } from 'typed-redux-saga/macro';
+import { call, put, select, takeEvery } from 'typed-redux-saga/macro';
 import { RootState } from '../reducers';
+import { ensureError } from '../utils';
 import {
     EditorActionType,
     EditorOpenAction,
     EditorReloadProgramAction,
     EditorSaveAsAction,
+    didFailToSaveAs,
+    didSaveAs,
 } from './actions';
 
 const decoder = new TextDecoder();
@@ -37,7 +40,42 @@ function* saveAs(_action: EditorSaveAsAction): Generator {
 
     const data = editor.getValue();
     const blob = new Blob([data], { type: 'text/x-python;charset=utf-8' });
-    FileSaver.saveAs(blob, 'main.py');
+
+    if (window.showSaveFilePicker) {
+        // This uses https://wicg.github.io/file-system-access which is not
+        // available in all browsers
+        try {
+            const handle = yield* call(() =>
+                window.showSaveFilePicker({
+                    suggestedName: 'main.py',
+                    types: [
+                        {
+                            accept: { 'text/x-python': '.py' },
+                            // TODO: translate description
+                            description: 'Python Files',
+                        },
+                    ],
+                }),
+            );
+
+            const writeable = yield* call(() => handle.createWritable());
+            yield* call(() => writeable.write(blob));
+            yield* call(() => writeable.close());
+        } catch (err) {
+            yield* put(didFailToSaveAs(ensureError(err)));
+            return;
+        }
+    } else {
+        // this is a fallback to use the standard browser download mechanism
+        try {
+            FileSaver.saveAs(blob, 'main.py');
+        } catch (err) {
+            yield* put(didFailToSaveAs(ensureError(err)));
+            return;
+        }
+    }
+
+    yield* put(didSaveAs());
 }
 
 function* reloadProgram(_action: EditorReloadProgramAction): Generator {