Changes based on review for #4

.travis.yml

@@ -9,7 +9,7 @@ cache:
   directories:
     - $HOME/.pub-cache
 
-script:
-  - dartanalyzer --fatal-warnings ./
-  - dartfmt -n --set-exit-if-changed .
-  - pub run test
+dart_task:
+  - dartanalyzer: --fatal-warnings ./
+  - dartfmt
+  - test

README.md

@@ -1,7 +1,9 @@
 # Sass Modules Migrator
 
 This tool is designed to help migrate stylesheets from the old `@import`
-functionality to the new module system.
+functionality to [the new module system][module-spec].
 
 This is still a work-in-progress, but should eventually implement everything
 described in [sass/sass#2575](https://github.com/sass/sass/issues/2575).
+
+[module-spec]: https://github.com/sass/language/blob/master/accepted/module-system.md

bin/sass_module_migrator.dart

@@ -26,15 +26,14 @@ void main(List<String> args) {
   var argResults = argParser.parse(args);
 
   if (argResults['help'] == true || argResults.rest.isEmpty) {
-    print('Migrates one or more .scss files to the new module system.\n\n'
+    print('Migrates one or more Sass files to the new module system.\n\n'
         'Usage: sass_migrate_to_modules [options] <entrypoint.scss ...>\n\n'
         '${argParser.usage}');
     exitCode = 64;
     return;
   }
 
-  var migrated = Migrator().runMigrations(argResults.rest,
-      migrateDependencies: argResults['recursive']);
+  var migrated = migrateFiles(argResults.rest);
 
   if (migrated.isEmpty) {
     print('Nothing to migrate!');

lib/src/local_scope.dart

@@ -0,0 +1,38 @@
+// Copyright 2019 Google LLC
+//
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file or at
+// https://opensource.org/licenses/MIT.
+
+import 'utils.dart';
+
+/// Keeps track of the scope of any members declared at the current level of
+/// the stylesheet.
+class LocalScope {
+  /// The parent of this scope, or null if this scope is only nested one level
+  /// from the root of the file.
+  final LocalScope parent;
+
+  /// Variables defined in this scope.
+  final variables = normalizedSet();
+
+  /// Mixins defined in this scope.
+  final mixins = normalizedSet();
+
+  /// Functions defined in this scope.
+  final functions = normalizedSet();
+
+  LocalScope(this.parent);
+
+  /// Returns whether a variable [name] exists somewhere within this scope.
+  bool isLocalVariable(String name) =>
+      variables.contains(name) || (parent?.isLocalVariable(name) ?? false);
+
+  /// Returns whether a mixin [name] exists somewhere within this scope.
+  bool isLocalMixin(String name) =>
+      variables.contains(name) || (parent?.isLocalMixin(name) ?? false);
+
+  /// Returns whether a function [name] exists somewhere within this scope.
+  bool isLocalFunction(String name) =>
+      variables.contains(name) || (parent?.isLocalFunction(name) ?? false);
+}