Allow command-line API to pass in selection to preserve. Fix #194.

test/command_line_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 library dart_style.test.command_line;
 
 import 'dart:convert';
 
 import 'package:path/path.dart' as p;
 import 'package:scheduled_test/descriptor.dart' as d;
@@ skipping 129 matching lines @@
 
       var process = runFormatterOnDir(["--machine"]);
 
       // The order isn't specified.
       process.stdout.expect(either(jsonA, jsonB));
       process.stdout.expect(either(jsonA, jsonB));
       process.shouldExit();
     });
   });
 
+  group("--preserve", () {
+    test("errors if given paths.", () {
+      var process = runFormatter(["--preserve", "path", "another"]);
+      process.shouldExit(64);
+    });
+
+    test("errors on wrong number of components.", () {
+      var process = runFormatter(["--preserve", "1"]);
+      process.shouldExit(64);
+
+      process = runFormatter(["--preserve", "1:2:3"]);
+      process.shouldExit(64);
+    });
+
+    test("errors on non-integer component.", () {
+      var process = runFormatter(["--preserve", "1:2.3"]);
+      process.shouldExit(64);
+    });
+
+    test("updates selection.", () {
+      var process = runFormatter(["--preserve", "6:10", "-m"]);
+      process.writeLine(unformattedSource);
+      process.closeStdin();
+
+      var json = JSON.encode({
+        "path": "<stdin>",
+        "source": formattedSource,
+        "selection": {"offset": 5, "length": 9}
+      });
+
+      process.stdout.expect(json);
+      process.shouldExit();
+    });
+  });
+
   group("with no paths", () {
     test("errors on --overwrite.", () {
       var process = runFormatter(["--overwrite"]);
       process.shouldExit(64);
     });
 
     test("reads from stdin.", () {
       var process = runFormatter();
       process.writeLine(unformattedSource);
       process.closeStdin();
 
       // No trailing newline at the end.
       process.stdout.expect(formattedSource.trimRight());
       process.shouldExit();
     });
   });
 }