Support compiling entire directories at once

Partially addresses #264

CHANGELOG.md

@@ -6,6 +6,10 @@
   `sass input.scss:output.css`. Note that unlike Ruby Sass, this *always*
   compiles files by default regardless of when they were modified.
 
+  This syntax also supports compiling entire directories at once. For example,
+  `sass templates/stylesheets:public/css` compiles all non-partial Sass files
+  in `templates/stylesheets` to CSS files in `public/css`.
+
 ## 1.3.2
 
 * Add support for `@elseif` as an alias of `@else if`. This is not an

lib/src/executable.dart

@@ -65,8 +65,8 @@ main(List<String> args) async {
     }
   } on UsageException catch (error) {
     print("${error.message}\n");
-    print("Usage: sass <input> [output]\n"
-        "       sass <input>:<output> <input>:<output>\n");
+    print("Usage: sass <input.scss> [output.css]\n"
+        "       sass <input.scss>:<output.css> <input/>:<output/>\n");
     print(ExecutableOptions.usage);
     exitCode = 64;
   } catch (error, stackTrace) {

lib/src/executable_options.dart

@@ -178,6 +178,10 @@ class ExecutableOptions {
 
     if (stdin) _fail('--stdin may not be used with ":" arguments.');
 
+    // Track [seen] separately from `sourcesToDestinations.keys` because we want
+    // to report errors for sources as users entered them, rather than after
+    // directories have been resolved.
+    var seen = new Set<String>();
     var sourcesToDestinations = <String, String>{};
     for (var argument in _options.rest) {
       var components = argument.split(":");
@@ -186,19 +190,43 @@ class ExecutableOptions {
       }
       assert(components.length == 2);
 
-      var source = components.first == '-' ? null : components.first;
-      if (sourcesToDestinations.containsKey(source)) {
-        _fail('Duplicate source "${components.first}".');
+      var source = components.first;
+      var destination = components.last;
+      if (!seen.add(source)) {
+        _fail('Duplicate source "${source}".');
       }
 
-      sourcesToDestinations[source] = components.last;
+      if (source == '-') {
+        sourcesToDestinations[null] = destination;
+      } else if (dirExists(source)) {
+        sourcesToDestinations.addAll(_listSourceDirectory(source, destination));
+      } else {
+        sourcesToDestinations[source] = destination;
+      }
     }
     _sourcesToDestinations = new Map.unmodifiable(sourcesToDestinations);
     return _sourcesToDestinations;
   }
 
   Map<String, String> _sourcesToDestinations;
 
+  /// Returns the sub-map of [sourcesToDestinations] for the given [source] and
+  /// [destination] directories.
+  Map<String, String> _listSourceDirectory(String source, String destination) {
+    var map = <String, String>{};
+    for (var path in listDir(source)) {
+      var basename = p.basename(path);
+      if (basename.startsWith("_")) continue;
+
+      var extension = p.extension(path);
+      if (extension != ".scss" && extension != ".sass") continue;
+
+      map[path] = p.join(
+          destination, p.setExtension(p.relative(path, from: source), '.css'));
+    }
+    return map;
+  }
+
   /// Whether to emit a source map file.
   bool get emitSourceMap {
     if (!(_options['source-map'] as bool)) {

lib/src/io/interface.dart

@@ -65,5 +65,9 @@ bool dirExists(String path) => null;
 /// necessary.
 void ensureDir(String path) => null;
 
+/// Recursively lists the files (not sub-directories) of the directory at
+/// [path].
+Iterable<String> listDir(String path) => null;
+
 /// Gets and sets the exit code that the process will use when it exits.
 int exitCode;

lib/src/io/node.dart

@@ -18,6 +18,14 @@ class _FS {
   external void writeFileSync(String path, String data);
   external bool existsSync(String path);
   external void mkdirSync(String path);
+  external _Stat statSync(String path);
+  external List<String> readdirSync(String path);
+}
+
+@JS()
+class _Stat {
+  external bool isFile();
+  external bool isDirectory();
 }
 
 @JS()
@@ -135,9 +143,25 @@ String _cleanErrorMessage(_SystemError error) {
       error.message.length - ", ${error.syscall} '${error.path}'".length);
 }
 
-bool fileExists(String path) => _fs.existsSync(path);
+bool fileExists(String path) {
+  try {
+    return _fs.statSync(path).isFile();
+  } catch (error) {
+    var systemError = error as _SystemError;
+    if (systemError.code == 'ENOENT') return false;
+    rethrow;
+  }
+}
 
-bool dirExists(String path) => _fs.existsSync(path);
+bool dirExists(String path) {
+  try {
+    return _fs.statSync(path).isDirectory();
+  } catch (error) {
+    var systemError = error as _SystemError;
+    if (systemError.code == 'ENOENT') return false;
+    rethrow;
+  }
+}
 
 void ensureDir(String path) {
   return _systemErrorToFileSystemException(() {
@@ -153,6 +177,14 @@ void ensureDir(String path) {
   });
 }
 
+Iterable<String> listDir(String path) {
+  Iterable<String> list(String path) => _fs
+      .readdirSync(path)
+      .expand((path) => dirExists(path) ? listDir(path) : [path]);
+
+  return _systemErrorToFileSystemException(() => list(path));
+}
+
 /// Runs callback and converts any [_SystemError]s it throws into
 /// [FileSystemException]s.
 T _systemErrorToFileSystemException<T>(T callback()) {

lib/src/io/vm.dart

@@ -56,3 +56,8 @@ bool dirExists(String path) => new io.Directory(path).existsSync();
 
 void ensureDir(String path) =>
     new io.Directory(path).createSync(recursive: true);
+
+Iterable<String> listDir(String path) => new io.Directory(path)
+    .listSync(recursive: true)
+    .where((entity) => entity is io.File)
+    .map((entity) => entity.path);

test/cli_shared.dart

@@ -213,6 +213,72 @@ void sharedTests(Future<TestProcess> runSass(Iterable<String> arguments)) {
       await d.file("out2.css.map", contains("test2.scss")).validate();
     });
 
+    group("with a directory argument", () {
+      test("compiles all the stylesheets in the directory", () async {
+        await d.dir("in", [
+          d.file("test1.scss", "a {b: c}"),
+          d.file("test2.sass", "x\n  y: z")
+        ]).create();
+
+        var sass = await runSass(["--no-source-map", "in:out"]);
+        expect(sass.stdout, emitsDone);
+        await sass.shouldExit(0);
+
+        await d.dir("out", [
+          d.file("test1.css", equalsIgnoringWhitespace("a { b: c; }")),
+          d.file("test2.css", equalsIgnoringWhitespace("x { y: z; }"))
+        ]).validate();
+      });
+
+      test("creates subdirectories in the destination", () async {
+        await d.dir("in", [
+          d.dir("sub", [d.file("test.scss", "a {b: c}")])
+        ]).create();
+
+        var sass = await runSass(["--no-source-map", "in:out"]);
+        expect(sass.stdout, emitsDone);
+        await sass.shouldExit(0);
+
+        await d.dir("out", [
+          d.dir("sub",
+              [d.file("test.css", equalsIgnoringWhitespace("a { b: c; }"))])
+        ]).validate();
+      });
+
+      test("ignores partials", () async {
+        await d.dir("in", [
+          d.file("_fake.scss", "a {b:"),
+          d.file("real.scss", "x {y: z}")
+        ]).create();
+
+        var sass = await runSass(["--no-source-map", "in:out"]);
+        expect(sass.stdout, emitsDone);
+        await sass.shouldExit(0);
+
+        await d.dir("out", [
+          d.file("real.css", equalsIgnoringWhitespace("x { y: z; }")),
+          d.nothing("fake.css"),
+          d.nothing("_fake.css")
+        ]).validate();
+      });
+
+      test("ignores files without a Sass extension", () async {
+        await d.dir("in", [
+          d.file("fake.szss", "a {b:"),
+          d.file("real.scss", "x {y: z}")
+        ]).create();
+
+        var sass = await runSass(["--no-source-map", "in:out"]);
+        expect(sass.stdout, emitsDone);
+        await sass.shouldExit(0);
+
+        await d.dir("out", [
+          d.file("real.css", equalsIgnoringWhitespace("x { y: z; }")),
+          d.nothing("fake.css")
+        ]).validate();
+      });
+    });
+
     group("reports all", () {
       test("file-not-found errors", () async {
         var sass =