Switch (partially) to sass_builder plugin

Now the global style sheet is built automatically when any of its
SASS files are modified. A project that uses this will have to
creates its own web/theme.scss and import our main scss file to
use it.

I haven't tested this on component SCSS yet.

lib/src/modular-admin/modular-admin.scss

@@ -1,45 +1,45 @@
 /*
  * Import mixins.
  */
-@import 'bootstrap/variables';
-@import 'bootstrap/mixins';
-@import 'modular-admin/mixins';
+@import '../bootstrap/variables';
+@import '../bootstrap/mixins';
+@import 'mixins';
 
 /*
  * Import all of Open Sans.
  */
 $OpenSansPath: "../open-sans/fonts" !default;
 $OpenSansVersion: "1.1.0" !default;
 
-@import 'open-sans/sass/mixins';
-@import 'open-sans/sass/Light';
-@import 'open-sans/sass/LightItalic';
-@import 'open-sans/sass/Regular';
-@import 'open-sans/sass/Italic';
-@import 'open-sans/sass/Semibold';
-@import 'open-sans/sass/SemiboldItalic';
-@import 'open-sans/sass/Bold';
-@import 'open-sans/sass/BoldItalic';
-@import 'open-sans/sass/ExtraBold';
-@import 'open-sans/sass/ExtraBoldItalic';
+@import '../open-sans/sass/mixins';
+@import '../open-sans/sass/Light';
+@import '../open-sans/sass/LightItalic';
+@import '../open-sans/sass/Regular';
+@import '../open-sans/sass/Italic';
+@import '../open-sans/sass/Semibold';
+@import '../open-sans/sass/SemiboldItalic';
+@import '../open-sans/sass/Bold';
+@import '../open-sans/sass/BoldItalic';
+@import '../open-sans/sass/ExtraBold';
+@import '../open-sans/sass/ExtraBoldItalic';
 
 /*
  * Import some things we need from Bootstrap.
  */
 
 $enable-flex: true;
-@import 'bootstrap/reboot';
-@import 'bootstrap/normalize';
-@import 'bootstrap/grid';
-@import 'bootstrap/code';
-@import 'bootstrap/type';
-@import 'bootstrap/utilities';
-@import 'bootstrap/list-group';
+@import '../bootstrap/reboot';
+@import '../bootstrap/normalize';
+@import '../bootstrap/grid';
+@import '../bootstrap/code';
+@import '../bootstrap/type';
+@import '../bootstrap/utilities';
+@import '../bootstrap/list-group';
 
 /*
  * Import Modular Admin.
  */
-@import 'modular-admin/theme';
-@import 'modular-admin/grid';
-@import 'modular-admin/document';
-@import 'modular-admin/typography';
+@import 'theme';
+@import 'grid';
+@import 'document';
+@import 'typography';

pubspec.yaml

@@ -17,3 +17,4 @@ dev_dependencies:
   build_runner: ^1.0.0
   build_test: ^0.10.2
   build_web_compilers: ^0.4.0
+  sass_builder: ^2.1.2

sass_builder.build.yaml

@@ -0,0 +1,10 @@
+builders:
+  sass_builder:
+    target: "sass_builder"
+    import: "package:sass_builder/sass_builder.dart"
+    builder_factories: ["sassBuilder"]
+    auto_apply: dependents
+    build_extensions:
+      .scss: [".css"]
+      .sass: [".css"]
+build_to: source

tool/build-styles.dart

@@ -6,7 +6,6 @@ import 'package:path/path.dart' as path;
 main (List<String> rawArgs) {
     ArgResults args = _parseArgs(rawArgs);
     buildComponentStyles(args['debug']);
-    buildSharedStyles(args['debug']);
 }
 
 /// Build a stylesheet for each component.
@@ -60,60 +59,6 @@ buildComponentStyles(bool debug) {
     }
 }
 
-/// Build a stylesheet for each theme.
-buildSharedStyles(bool debug) {
-    print('Building shared stylesheets…');
-    var themeDir = new Directory(_getPath('lib/src/modular-admin'));
-    var cssDir = _getPath('lib/css');
-    var includeDir = _getPath('lib/src');
-    var sourcePaths = new List<String>();
-
-    for (FileSystemEntity entity in themeDir.listSync()) {
-        String basename = path.basename(entity.path);
-        String extension = path.extension(entity.path);
-
-        if (basename.startsWith('_') || extension != '.scss') {
-            continue;
-        }
-
-        sourcePaths.add(entity.path);
-    }
-
-    sourcePaths.sort();
-
-    for (String sourcePath in sourcePaths) {
-        String basename = path.basename(sourcePath);
-        String themeName = basename.substring(0, basename.length - 5);
-        String destName = themeName + '.css';
-        String destPath = path.join(cssDir, themeName + '.css');
-
-        // TODO temporary hack, always build theme:
-        bool cached = false;//_styleSheetIsCurrent(sourcePath, destPath);
-
-        print(' * lib/src/modular-admin/' + basename +
-              ' → lib/css/' + destName +
-              (cached ? ' (cached)' : ''));
-
-        if (cached) {
-            continue;
-        }
-
-        var sasscArgs = ['-I', includeDir];
-
-        if (!debug) {
-            sasscArgs.addAll(['-t', 'compressed']);
-        }
-
-        sasscArgs.addAll([sourcePath, destPath]);
-        var result = Process.runSync('sassc', sasscArgs);
-        if (result.exitCode != 0) {
-            print('ERROR: Failed to compile ' + sourcePath);
-            print(result.stderr);
-            exit(1);
-        }
-    }
-}
-
 /// Construct a full path from a path relative to the project toot.
 String _getPath(String relPath) {
     var scriptPath = Platform.script.toFilePath();