data_transfer_flutter 0.2.0: exportTextFile + mime types

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WzxdWXTUM9dpnCS2wtFkx4

data_transfer_flutter/README.md

@@ -11,7 +11,7 @@ dependencies:
   data_transfer_flutter:
     git:
       url: https://github.com/kuhyx/utils
-      ref: data_transfer_flutter-v0.1.0
+      ref: data_transfer_flutter-v0.2.0
       path: data_transfer_flutter
 ```
 
@@ -26,6 +26,7 @@ final map = await pickJson(); // null when cancelled
   use the system "Save as" document picker (`file_picker` `saveFile`, i.e.
   ACTION_CREATE_DOCUMENT), desktop a save dialog (`file_selector`), web a
   browser download. Returns false when cancelled.
+- `exportTextFile` does the same for any text (`text/csv`, `text/calendar`).
 - `shareJson` is an optional second action (share sheet). It is never the
   only way out: a stock phone's share sheet has no local save target.
 - `pickJson` / `pickJsonText` use the system open-document picker.

data_transfer_flutter/lib/src/json_type_group.dart

@@ -9,3 +9,19 @@ const jsonTypeGroup = XTypeGroup(
   uniformTypeIdentifiers: ['public.json'],
   mimeTypes: ['application/json'],
 );
+
+/// The save-dialog filter for [fileName] holding [mimeType] data.
+///
+/// Keyed on the file's own extension so a CSV export is not offered under a
+/// JSON filter; a name with no extension accepts any type.
+XTypeGroup saveTypeGroup(String fileName, String mimeType) {
+  final dot = fileName.lastIndexOf('.');
+  final extension = dot > 0 && dot < fileName.length - 1
+      ? fileName.substring(dot + 1).toLowerCase()
+      : null;
+  return XTypeGroup(
+    label: extension?.toUpperCase(),
+    extensions: extension == null ? null : [extension],
+    mimeTypes: [mimeType],
+  );
+}

data_transfer_flutter/lib/src/platform.dart

@@ -9,14 +9,22 @@ abstract interface class DataTransferPlatform {
   /// Android/iOS: the system "Save as" document picker (device storage).
   /// Desktop: a save dialog. Web: a browser download. Returns false when the
   /// user cancelled.
-  Future<bool> saveText({required String fileName, required String text});
+  Future<bool> saveText({
+    required String fileName,
+    required String text,
+    String mimeType = 'application/json',
+  });
 
   /// Offers [text] as [fileName] to the share sheet, where the host has one.
   ///
   /// A second action only: a share sheet can route the data to cloud apps, so
   /// it never replaces [saveText]. Hosts without a sheet fall back to
   /// [saveText].
-  Future<bool> shareText({required String fileName, required String text});
+  Future<bool> shareText({
+    required String fileName,
+    required String text,
+    String mimeType = 'application/json',
+  });
 
   /// Opens the system open-document picker and returns the file's text, or
   /// null when the user cancelled.

data_transfer_flutter/lib/src/platform_io.dart

@@ -12,11 +12,19 @@ import 'package:share_plus/share_plus.dart';
 
 /// Writes [bytes] through the system "Save as" picker; false on cancel.
 typedef DocumentSaver =
-    Future<bool> Function({required String fileName, required Uint8List bytes});
+    Future<bool> Function({
+      required String fileName,
+      required Uint8List bytes,
+      required String mimeType,
+    });
 
 /// Offers [text] as a file named [fileName] to the share sheet.
 typedef SheetSharer =
-    Future<bool> Function({required String fileName, required String text});
+    Future<bool> Function({
+      required String fileName,
+      required String text,
+      required String mimeType,
+    });
 
 /// The platform for hosts that have `dart:io`.
 DataTransferPlatform createDefaultPlatform() => IoDataTransferPlatform();
@@ -46,16 +54,18 @@ class IoDataTransferPlatform implements DataTransferPlatform {
   Future<bool> saveText({
     required String fileName,
     required String text,
+    String mimeType = 'application/json',
   }) async {
     if (_isMobile) {
       return await _documentSaver(
         fileName: fileName,
         bytes: Uint8List.fromList(utf8.encode(text)),
+        mimeType: mimeType,
       );
     }
     final location = await getSaveLocation(
       suggestedName: fileName,
-      acceptedTypeGroups: const [jsonTypeGroup],
+      acceptedTypeGroups: [saveTypeGroup(fileName, mimeType)],
     );
     if (location == null) return false;
     await File(location.path).writeAsString(text);
@@ -63,10 +73,13 @@ class IoDataTransferPlatform implements DataTransferPlatform {
   }
 
   @override
-  Future<bool> shareText({required String fileName, required String text}) =>
-      _isMobile
-      ? _sheetSharer(fileName: fileName, text: text)
-      : saveText(fileName: fileName, text: text);
+  Future<bool> shareText({
+    required String fileName,
+    required String text,
+    String mimeType = 'application/json',
+  }) => _isMobile
+      ? _sheetSharer(fileName: fileName, text: text, mimeType: mimeType)
+      : saveText(fileName: fileName, text: text, mimeType: mimeType);
 
   @override
   Future<String?> pickText() async {
@@ -81,11 +94,12 @@ class IoDataTransferPlatform implements DataTransferPlatform {
 Future<bool> _saveViaDocumentPicker({
   required String fileName,
   required Uint8List bytes,
+  required String mimeType,
 }) async {
   final saved = await FilePicker.saveFile(
     fileName: fileName,
     bytes: bytes,
-    mimeType: 'application/json',
+    mimeType: mimeType,
   );
   return saved != null;
 }
@@ -93,12 +107,13 @@ Future<bool> _saveViaDocumentPicker({
 Future<bool> _shareViaSheet({
   required String fileName,
   required String text,
+  required String mimeType,
 }) async {
   final dir = await getTemporaryDirectory();
   final file = File(p.join(dir.path, fileName));
   await file.writeAsString(text);
   await SharePlus.instance.share(
-    ShareParams(files: [XFile(file.path, mimeType: 'application/json')]),
+    ShareParams(files: [XFile(file.path, mimeType: mimeType)]),
   );
   return true;
 }

data_transfer_flutter/lib/src/platform_web.dart

@@ -16,20 +16,24 @@ class WebDataTransferPlatform implements DataTransferPlatform {
   Future<bool> saveText({
     required String fileName,
     required String text,
+    String mimeType = 'application/json',
   }) async {
     // `saveTo` on web clicks a synthetic anchor: the path is ignored and the
     // browser's download UI decides where the file lands.
     await XFile.fromData(
       utf8.encode(text),
-      mimeType: 'application/json',
+      mimeType: mimeType,
       name: fileName,
     ).saveTo('');
     return true;
   }
 
   @override
-  Future<bool> shareText({required String fileName, required String text}) =>
-      saveText(fileName: fileName, text: text);
+  Future<bool> shareText({
+    required String fileName,
+    required String text,
+    String mimeType = 'application/json',
+  }) => saveText(fileName: fileName, text: text, mimeType: mimeType);
 
   @override
   Future<String?> pickText() async {

data_transfer_flutter/lib/src/transfer.dart

@@ -21,7 +21,19 @@ Future<bool> exportJson({
 
 /// [exportJson] for an already-encoded JSON string.
 Future<bool> exportJsonText({required String fileName, required String text}) =>
-    DataTransfer.platform.saveText(fileName: fileName, text: text);
+    exportTextFile(fileName: fileName, text: text);
+
+/// Saves any text file ([mimeType], e.g. `text/csv`) to device storage, with
+/// the same host behaviour as [exportJson]. False when cancelled.
+Future<bool> exportTextFile({
+  required String fileName,
+  required String text,
+  String mimeType = 'application/json',
+}) => DataTransfer.platform.saveText(
+  fileName: fileName,
+  text: text,
+  mimeType: mimeType,
+);
 
 /// Optional second action: offers [json] to the share sheet.
 Future<bool> shareJson({

data_transfer_flutter/pubspec.yaml

@@ -4,7 +4,7 @@ description: >-
   Flutter apps: system Save-as on Android/iOS (never cloud-only), a save
   dialog on desktop, a download on web, plus a versioned export envelope.
 publish_to: 'none'
-version: 0.1.0
+version: 0.2.0
 
 environment:
   sdk: ^3.12.2

data_transfer_flutter/test/io_platform_test.dart

@@ -2,6 +2,7 @@ import 'dart:convert';
 import 'dart:io';
 import 'dart:typed_data';
 
+import 'package:data_transfer_flutter/src/json_type_group.dart';
 import 'package:data_transfer_flutter/src/platform_io.dart';
 import 'package:file_selector_platform_interface/file_selector_platform_interface.dart';
 import 'package:flutter_test/flutter_test.dart';
@@ -46,6 +47,17 @@ void main() {
   group('desktop', () {
     final desktop = IoDataTransferPlatform(isMobile: false);
 
+    test('the save dialog is typed by the file name and mime type', () {
+      final group = saveTypeGroup('punchme.csv', 'text/csv');
+
+      expect(group.extensions, ['csv']);
+      expect(group.mimeTypes, ['text/csv']);
+    });
+
+    test('a name without an extension accepts any type', () {
+      expect(saveTypeGroup('README', 'text/plain').extensions, isNull);
+    });
+
     test('save writes to the chosen path and suggests the name', () async {
       final path = '${temp.path}/out.json';
       selector.saveLocation = FileSaveLocation(path);
@@ -91,20 +103,28 @@ void main() {
       'save hands UTF-8 bytes to the document saver, not file_selector',
       () async {
         String? name;
+        String? mime;
         List<int>? captured;
         final mobile = IoDataTransferPlatform(
           isMobile: true,
-          documentSaver: ({required fileName, required bytes}) async {
-            name = fileName;
-            captured = bytes;
-            return true;
-          },
+          documentSaver:
+              ({required fileName, required bytes, required mimeType}) async {
+                name = fileName;
+                mime = mimeType;
+                captured = bytes;
+                return true;
+              },
         );
 
-        final saved = await mobile.saveText(fileName: 'm.json', text: 'zażółć');
+        final saved = await mobile.saveText(
+          fileName: 'm.json',
+          text: 'zażółć',
+          mimeType: 'text/csv',
+        );
 
         expect(saved, isTrue);
         expect(name, 'm.json');
+        expect(mime, 'text/csv');
         expect(utf8.decode(captured!), 'zażółć');
         expect(selector.saveRequests, isEmpty);
       },
@@ -113,7 +133,9 @@ void main() {
     test('a cancelled document picker reports false', () async {
       final mobile = IoDataTransferPlatform(
         isMobile: true,
-        documentSaver: ({required fileName, required bytes}) async => false,
+        documentSaver:
+            ({required fileName, required bytes, required mimeType}) async =>
+                false,
       );
 
       expect(await mobile.saveText(fileName: 'm.json', text: '{}'), isFalse);
@@ -121,16 +143,20 @@ void main() {
 
     test('share goes through the share sheet seam', () async {
       (String, String)? seen;
+      String? sharedMime;
       final mobile = IoDataTransferPlatform(
         isMobile: true,
-        sheetSharer: ({required fileName, required text}) async {
-          seen = (fileName, text);
-          return true;
-        },
+        sheetSharer:
+            ({required fileName, required text, required mimeType}) async {
+              seen = (fileName, text);
+              sharedMime = mimeType;
+              return true;
+            },
       );
 
       expect(await mobile.shareText(fileName: 's.json', text: '1'), isTrue);
       expect(seen, ('s.json', '1'));
+      expect(sharedMime, 'application/json');
     });
   });
 }

data_transfer_flutter/test/support/fake_platform.dart

@@ -11,6 +11,9 @@ class FakePlatform implements DataTransferPlatform {
   /// `(fileName, text)` of every [saveText] call.
   final saves = <(String, String)>[];
 
+  /// The mime type of every [saveText] call, in order.
+  final saveMimes = <String>[];
+
   /// `(fileName, text)` of every [shareText] call.
   final shares = <(String, String)>[];
 
@@ -18,8 +21,10 @@ class FakePlatform implements DataTransferPlatform {
   Future<bool> saveText({
     required String fileName,
     required String text,
+    String mimeType = 'application/json',
   }) async {
     saves.add((fileName, text));
+    saveMimes.add(mimeType);
     return accept;
   }
 
@@ -27,6 +32,7 @@ class FakePlatform implements DataTransferPlatform {
   Future<bool> shareText({
     required String fileName,
     required String text,
+    String mimeType = 'application/json',
   }) async {
     shares.add((fileName, text));
     return accept;

data_transfer_flutter/test/transfer_test.dart

@@ -45,6 +45,26 @@ void main() {
     });
   });
 
+  group('exportTextFile', () {
+    test('saves non-JSON text with its own mime type', () async {
+      final saved = await exportTextFile(
+        fileName: 'a.csv',
+        text: 'a,b\n',
+        mimeType: 'text/csv',
+      );
+
+      expect(saved, isTrue);
+      expect(fake.saves.single, ('a.csv', 'a,b\n'));
+      expect(fake.saveMimes.single, 'text/csv');
+    });
+
+    test('exportJsonText keeps the JSON mime type', () async {
+      await exportJsonText(fileName: 'a.json', text: '{}');
+
+      expect(fake.saveMimes.single, 'application/json');
+    });
+  });
+
   group('shareJson', () {
     test('uses the share action, not save', () async {
       final shared = await shareJson(fileName: 'c.json', json: {'k': 2});

sync_settings_ui/pubspec.yaml

@@ -5,7 +5,7 @@ description: >-
   injected closures -- no keystore or platform plugin access lives in this
   package itself.
 publish_to: 'none'
-version: 0.5.0
+version: 0.5.1
 
 environment:
   sdk: ^3.12.2
@@ -19,7 +19,7 @@ dependencies:
   data_transfer_flutter:
     git:
       url: https://github.com/kuhyx/utils
-      ref: data_transfer_flutter-v0.1.0
+      ref: data_transfer_flutter-v0.2.0
       path: data_transfer_flutter
   flutter:
     sdk: flutter

sync_settings_ui/test/backup_slot_test.dart

@@ -85,6 +85,7 @@ class _FakePlatform implements DataTransferPlatform {
   Future<bool> saveText({
     required String fileName,
     required String text,
+    String mimeType = 'application/json',
   }) async {
     saved.add((fileName, text));
     return true;
@@ -94,6 +95,7 @@ class _FakePlatform implements DataTransferPlatform {
   Future<bool> shareText({
     required String fileName,
     required String text,
+    String mimeType = 'application/json',
   }) async => true;
 
   @override