Add support for "sass input.scss output.css" (#275)

Closes #274

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.1.0
+
+* The command-line executable can now be used to write an output file to disk
+  using `sass input.scss output.css`.
+
 ## 1.0.0
 
 **Initial stable release.**

lib/src/executable.dart

@@ -61,7 +61,10 @@ main(List<String> args) async {
   }
 
   var stdinFlag = options['stdin'] as bool;
-  if (options['help'] as bool || (options.rest.isEmpty && !stdinFlag)) {
+  if (options['help'] as bool ||
+      (stdinFlag
+          ? options.rest.length > 1
+          : options.rest.isEmpty || options.rest.length > 2)) {
     _printUsage(argParser, "Compile Sass to CSS.");
     exitCode = 64;
     return;
@@ -80,7 +83,9 @@ main(List<String> args) async {
   var asynchronous = options['async'] as bool;
   try {
     String css;
+    String destination;
     if (stdinFlag) {
+      if (options.rest.isNotEmpty) destination = options.rest.first;
       css = await _compileStdin(
           indented: indented,
           logger: logger,
@@ -88,8 +93,9 @@ main(List<String> args) async {
           loadPaths: loadPaths,
           asynchronous: asynchronous);
     } else {
-      var input = options.rest.first;
-      if (input == '-') {
+      var source = options.rest.first;
+      if (options.rest.length > 1) destination = options.rest.last;
+      if (source == '-') {
         css = await _compileStdin(
             indented: indented,
             logger: logger,
@@ -97,15 +103,19 @@ main(List<String> args) async {
             loadPaths: loadPaths,
             asynchronous: asynchronous);
       } else if (asynchronous) {
-        css = await compileAsync(input,
+        css = await compileAsync(source,
             logger: logger, style: style, loadPaths: loadPaths);
       } else {
         css =
-            compile(input, logger: logger, style: style, loadPaths: loadPaths);
+            compile(source, logger: logger, style: style, loadPaths: loadPaths);
       }
     }
 
-    if (css.isNotEmpty) print(css);
+    if (destination != null) {
+      writeFile(destination, css + "\n");
+    } else if (css.isNotEmpty) {
+      print(css);
+    }
   } on SassException catch (error, stackTrace) {
     stderr.writeln(error.toString(color: color));
 
@@ -192,6 +202,6 @@ Future<String> _compileStdin(
 /// Print the usage information for Sass, with [message] as a header.
 void _printUsage(ArgParser parser, String message) {
   print("$message\n");
-  print("Usage: dart-sass <input>\n");
+  print("Usage: sass <input> [output]\n");
   print(parser.usage);
 }

lib/src/io/interface.dart

@@ -46,6 +46,11 @@ String get currentPath => null;
 /// the file isn't valid UTF-8.
 String readFile(String path) => null;
 
+/// Writes [contents] to the file at [path], encoded as UTF-8.
+///
+/// Throws a [FileSystemException] if writing fails.
+void writeFile(String path, String contents) => null;
+
 /// Reads from the standard input for the current process until it closes,
 /// returning the contents.
 Future<String> readStdin() async => null;

lib/src/io/node.dart

@@ -14,7 +14,7 @@ import '../util/path.dart';
 @JS()
 class _FS {
   external readFileSync(String path, [String encoding]);
-
+  external void writeFileSync(String path, String data);
   external bool existsSync(String path);
 }
 
@@ -102,6 +102,16 @@ _readFile(String path, [String encoding]) {
   }
 }
 
+void writeFile(String path, String contents) {
+  try {
+    return _fs.writeFileSync(path, contents);
+  } catch (error) {
+    var systemError = error as _SystemError;
+    throw new FileSystemException._(
+        _cleanErrorMessage(systemError), systemError.path);
+  }
+}
+
 Future<String> readStdin() async {
   var completer = new Completer<String>();
   String contents;

lib/src/io/vm.dart

@@ -41,6 +41,9 @@ String readFile(String path) {
   }
 }
 
+void writeFile(String path, String contents) =>
+    new io.File(path).writeAsStringSync(contents);
+
 Future<String> readStdin() async {
   var completer = new Completer<String>();
   completer.complete(await io.SYSTEM_ENCODING.decodeStream(io.stdin));

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.0.0
+version: 1.1.0-dev
 description: A Sass implementation in Dart.
 author: Dart Team <misc@dartlang.org>
 homepage: https://github.com/sass/dart-sass

test/cli_shared.dart

@@ -10,6 +10,14 @@ import 'package:test_process/test_process.dart';
 
 /// Defines test that are shared between the Dart and Node.js CLI test suites.
 void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
+  /// Runs the executable on [arguments] plus an output file, then verifies that
+  /// the contents of the output file match [expected].
+  Future expectCompiles(List<String> arguments, expected) async {
+    var sass = await runSass(arguments.toList()..add("out.css"));
+    await sass.shouldExit(0);
+    await d.file("out.css", expected).validate();
+  }
+
   test("--help prints the usage documentation", () async {
     // Checking the entire output is brittle, so just do a sanity check to make
     // sure it's not totally busted.
@@ -34,6 +42,15 @@ void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
     await sass.shouldExit(0);
   });
 
+  test("writes a CSS file to disk", () async {
+    await d.file("test.scss", "a {b: 1 + 2}").create();
+
+    var sass = await runSass(["test.scss", "out.css"]);
+    expect(sass.stdout, emitsDone);
+    await sass.shouldExit(0);
+    await d.file("out.css", equalsIgnoringWhitespace("a { b: 3; }")).validate();
+  });
+
   test("compiles from stdin with the magic path -", () async {
     var sass = await runSass(["-"]);
     sass.stdin.writeln("a {b: 1 + 2}");
@@ -54,15 +71,8 @@ void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
 
       await d.dir("dir", [d.file("test.scss", "a {b: 1 + 2}")]).create();
 
-      var sass = await runSass(["test.scss", "test.css"]);
-      expect(
-          sass.stdout,
-          emitsInOrder([
-            "a {",
-            "  b: 3;",
-            "}",
-          ]));
-      await sass.shouldExit(0);
+      await expectCompiles(
+          ["test.scss"], equalsIgnoringWhitespace("a { b: 3; }"));
     });
 
     test("from the load path", () async {
@@ -70,15 +80,8 @@ void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
 
       await d.dir("dir", [d.file("test2.scss", "a {b: c}")]).create();
 
-      var sass = await runSass(["--load-path", "dir", "test.scss", "test.css"]);
-      expect(
-          sass.stdout,
-          emitsInOrder([
-            "a {",
-            "  b: c;",
-            "}",
-          ]));
-      await sass.shouldExit(0);
+      await expectCompiles(["--load-path", "dir", "test.scss"],
+          equalsIgnoringWhitespace("a { b: c; }"));
     });
 
     test("relative in preference to from the load path", () async {
@@ -87,15 +90,8 @@ void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
 
       await d.dir("dir", [d.file("test2.scss", "a {b: c}")]).create();
 
-      var sass = await runSass(["--load-path", "dir", "test.scss", "test.css"]);
-      expect(
-          sass.stdout,
-          emitsInOrder([
-            "x {",
-            "  y: z;",
-            "}",
-          ]));
-      await sass.shouldExit(0);
+      await expectCompiles(["--load-path", "dir", "test.scss"],
+          equalsIgnoringWhitespace("x { y: z; }"));
     });
 
     test("in load path order", () async {
@@ -104,22 +100,9 @@ void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
       await d.dir("dir1", [d.file("test2.scss", "a {b: c}")]).create();
       await d.dir("dir2", [d.file("test2.scss", "x {y: z}")]).create();
 
-      var sass = await runSass([
-        "--load-path",
-        "dir2",
-        "--load-path",
-        "dir1",
-        "test.scss",
-        "test.css"
-      ]);
-      expect(
-          sass.stdout,
-          emitsInOrder([
-            "x {",
-            "  y: z;",
-            "}",
-          ]));
-      await sass.shouldExit(0);
+      await expectCompiles(
+          ["--load-path", "dir2", "--load-path", "dir1", "test.scss"],
+          equalsIgnoringWhitespace("x { y: z; }"));
     });
   });
 
@@ -138,6 +121,18 @@ void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
       await sass.shouldExit(0);
     });
 
+    test("writes a CSS file to disk", () async {
+      var sass = await runSass(["--stdin", "out.css"]);
+      sass.stdin.writeln("a {b: 1 + 2}");
+      sass.stdin.close();
+      expect(sass.stdout, emitsDone);
+
+      await sass.shouldExit(0);
+      await d
+          .file("out.css", equalsIgnoringWhitespace("a { b: 3; }"))
+          .validate();
+    });
+
     test("uses the indented syntax with --indented", () async {
       var sass = await runSass(["--stdin", "--indented"]);
       sass.stdin.writeln("a\n  b: 1 + 2");
@@ -226,6 +221,20 @@ void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
       await sass.shouldExit(64);
     });
 
+    test("from too many positional arguments", () async {
+      var sass = await runSass(["abc", "def", "ghi"]);
+      expect(
+          sass.stdout, emitsThrough(contains("Print this usage information.")));
+      await sass.shouldExit(64);
+    });
+
+    test("from too many positional arguments with --stdin", () async {
+      var sass = await runSass(["--stdin", "abc", "def"]);
+      expect(
+          sass.stdout, emitsThrough(contains("Print this usage information.")));
+      await sass.shouldExit(64);
+    });
+
     test("from a file that doesn't exist", () async {
       var sass = await runSass(["asdf"]);
       expect(sass.stderr, emits(startsWith("Error reading asdf:")));