Implement writeAsString (#223)

Author: brianquinlan

pkgs/io_file/README.md

@@ -31,7 +31,7 @@ See
 |  rename               |         |   ✓   |   ✓   |   ✓   |    ✓    |            |              |
 |  set permissions      |         |       |       |       |         |            |              |
 |  write file (bytes)   |         |   ✓   |   ✓   |   ✓   |    ✓    |            |              |
-|  write file (string)  |         |       |       |       |         |            |              |
+|  write file (string)  |         |   ✓   |   ✓   |   ✓   |    ✓    |            |              |
 
 ### File
 

pkgs/io_file/lib/src/file_system.dart

@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:convert';
 import 'dart:typed_data';
 
 // TODO(brianquinlan): When we switch to using exception types outside of
@@ -141,7 +142,6 @@ base class FileSystem {
   /// Write the given bytes to a file.
   ///
   /// If `path` is a broken symlink and `mode` is [WriteMode.failExisting]:
-  ///
   /// - On Windows, the target of the symlink is created, using `data` as its
   ///   contents.
   /// - On POSIX, [writeAsBytes] throws `PathExistsException`.
@@ -152,4 +152,25 @@ base class FileSystem {
   ]) {
     throw UnsupportedError('writeAsBytes');
   }
+
+  /// Write the string to a file.
+  ///
+  /// If `path` is a broken symlink and `mode` is [WriteMode.failExisting]:
+  /// - On Windows, the target of the symlink is created, using `data` as its
+  ///   contents.
+  /// - On POSIX, [writeAsBytes] throws `PathExistsException`.
+  ///
+  /// `lineTerminator` is used to replace `'\n'` characters in `content`.
+  /// If `lineTerminator` is provided, then it must be one of `'\n'` or
+  /// `'\r\n'`. If `lineTerminator` is not provided then the platform line
+  /// ending is used, i.e. `'\r\n'` on Windows and `'\n'` everwhere else.
+  void writeAsString(
+    String path,
+    String contents, [
+    WriteMode mode = WriteMode.failExisting,
+    Encoding encoding = utf8,
+    String? lineTerminator,
+  ]) {
+    throw UnsupportedError('writeAsString');
+  }
 }

pkgs/io_file/lib/src/vm_posix_file_system.dart

@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:convert';
 import 'dart:ffi';
 import 'dart:io' as io;
 import 'dart:math';
@@ -251,4 +252,28 @@ base class PosixFileSystem extends FileSystem {
       stdlibc.close(fd);
     }
   }
+
+  @override
+  void writeAsString(
+    String path,
+    String contents, [
+    WriteMode mode = WriteMode.failExisting,
+    Encoding encoding = utf8,
+    String? lineTerminator,
+  ]) {
+    lineTerminator ??= '\n';
+    final List<int> data;
+    if (lineTerminator == '\n') {
+      data = encoding.encode(contents);
+    } else if (lineTerminator == '\r\n') {
+      data = encoding.encode(contents.replaceAll('\n', '\r\n'));
+    } else {
+      throw ArgumentError.value(lineTerminator, 'lineTerminator');
+    }
+    writeAsBytes(
+      path,
+      data is Uint8List ? data : Uint8List.fromList(data),
+      mode,
+    );
+  }
 }

pkgs/io_file/lib/src/vm_windows_file_system.dart

@@ -2,6 +2,7 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:convert';
 import 'dart:ffi';
 import 'dart:io' as io;
 import 'dart:math';
@@ -325,4 +326,28 @@ base class WindowsFileSystem extends FileSystem {
       win32.CloseHandle(f);
     }
   });
+
+  @override
+  void writeAsString(
+    String path,
+    String contents, [
+    WriteMode mode = WriteMode.failExisting,
+    Encoding encoding = utf8,
+    String? lineTerminator,
+  ]) {
+    lineTerminator ??= '\r\n';
+    final List<int> data;
+    if (lineTerminator == '\n') {
+      data = encoding.encode(contents);
+    } else if (lineTerminator == '\r\n') {
+      data = encoding.encode(contents.replaceAll('\n', '\r\n'));
+    } else {
+      throw ArgumentError.value(lineTerminator, 'lineTerminator');
+    }
+    writeAsBytes(
+      path,
+      data is Uint8List ? data : Uint8List.fromList(data),
+      mode,
+    );
+  }
 }