If no paths are provided, read source from stdin. Fix #165.

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;
 import 'package:scheduled_test/scheduled_test.dart';
 
 import 'utils.dart';
 
 void main() {
   setUpTestSuite();
 
   test("Exits with 0 on success.", () {
     d.dir("code", [
       d.file("a.dart", unformattedSource)
     ]).create();
 
-    var process = runFormatter();
+    var process = runFormatterOnDir();
     process.shouldExit(0);
   });
 
   test("Exits with 64 on a command line argument error.", () {
-    var process = runFormatter(["-wat"]);
+    var process = runFormatterOnDir(["-wat"]);
     process.shouldExit(64);
   });
 
   test("Exits with 65 on a parse error.", () {
     d.dir("code", [
       d.file("a.dart", "herp derp i are a dart")
     ]).create();
 
-    var process = runFormatter();
+    var process = runFormatterOnDir();
     process.shouldExit(65);
   });
 
   test("Errors if --dry-run and --overwrite are both passed.", () {
     d.dir("code", [
       d.file("a.dart", unformattedSource)
     ]).create();
 
-    var process = runFormatter(["--dry-run", "--overwrite"]);
+    var process = runFormatterOnDir(["--dry-run", "--overwrite"]);
     process.shouldExit(64);
   });
 
+  test("Errors if --dry-run and --machine are both passed.", () {
+    d.dir("code", [
+      d.file("a.dart", unformattedSource)
+    ]).create();
+
+    var process = runFormatterOnDir(["--dry-run", "--machine"]);
+    process.shouldExit(64);
+  });
+
+  test("Errors if --machine and --overwrite are both passed.", () {
+    d.dir("code", [
+      d.file("a.dart", unformattedSource)
+    ]).create();
+
+    var process = runFormatterOnDir(["--machine", "--overwrite"]);
+    process.shouldExit(64);
+  });
+
   test("Errors if --dry-run and --machine are both passed.", () {
     d.dir("code", [
       d.file("a.dart", unformattedSource)
     ]).create();
 
     var process = runFormatter(["--dry-run", "--machine"]);
     process.shouldExit(64);
   });
 
   test("Errors if --machine and --overwrite are both passed.", () {
     d.dir("code", [
       d.file("a.dart", unformattedSource)
     ]).create();
 
     var process = runFormatter(["--machine", "--overwrite"]);
     process.shouldExit(64);
   });
 
   group("--dry-run", () {
     test("prints names of files that would change.", () {
       d.dir("code", [
         d.file("a_bad.dart", unformattedSource),
         d.file("b_good.dart", formattedSource),
         d.file("c_bad.dart", unformattedSource),
         d.file("d_good.dart", formattedSource)
       ]).create();
 
-      var process = runFormatter(["--dry-run"]);
+      var process = runFormatterOnDir(["--dry-run"]);
       process.stdout.expect(p.join("code", "a_bad.dart"));
       process.stdout.expect(p.join("code", "c_bad.dart"));
       process.shouldExit();
     });
 
     test("does not modify files.", () {
       d.dir("code", [
         d.file("a.dart", unformattedSource)
       ]).create();
 
-      var process = runFormatter(["--dry-run"]);
+      var process = runFormatterOnDir(["--dry-run"]);
       process.stdout.expect(p.join("code", "a.dart"));
       process.shouldExit();
 
       d.dir('code', [
         d.file('a.dart', unformattedSource)
-    ]).validate();
+      ]).validate();
     });
   });
 
   group("--machine", () {
     test("writes each output as json", () {
       d.dir("code", [
         d.file("a.dart", unformattedSource),
         d.file("b.dart", unformattedSource)
       ]).create();
 
-      var process = runFormatter(["--machine", "code"]);
+      var process = runFormatterOnDir(["--machine"]);
 
       var json = {
         "path": p.join("code", "a.dart"),
         "source": formattedSource,
         "selection": {"offset": -1, "length": -1}
       };
 
       process.stdout.expect(JSON.encode(json));
 
       json["path"] = p.join("code", "b.dart");
       process.stdout.expect(JSON.encode(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();
+    });
+  });
 }