Add media query migrator (#228)

This PR adds a new `handleDeprecation` method to `Migrator`, which the
new migrator uses instead of attempting to duplicate the logic from the
parser.

CHANGELOG.md

@@ -1,3 +1,11 @@
+## 1.7.0
+
+### Media Logic Migrator
+
+* Adds a new migrator for migrating [deprecated `@media` query logic].
+
+[deprecated `@media` query logic]: https://sass-lang.com/d/media-logic
+
 ## 1.6.0
 
 ### Strict Unary Migrator

lib/src/migrator.dart

@@ -10,6 +10,7 @@ import 'package:meta/meta.dart';
 import 'package:path/path.dart' as p;
 import 'package:sass_api/sass_api.dart';
 import 'package:source_span/source_span.dart';
+import 'package:stack_trace/stack_trace.dart';
 
 import 'exception.dart';
 import 'io.dart';
@@ -57,6 +58,10 @@ abstract class Migrator extends Command<Map<Uri, String>> {
   Map<Uri, String> migrateFile(
       ImportCache importCache, Stylesheet stylesheet, Importer importer);
 
+  /// This is called whenever a deprecation warning is emitted during parsing.
+  @protected
+  void handleDeprecation(String message, FileSpan? span) {}
+
   /// Runs this migrator.
   ///
   /// Each entrypoint is migrated separately. If a stylesheet is migrated more
@@ -70,7 +75,8 @@ abstract class Migrator extends Command<Map<Uri, String>> {
     var importer = FilesystemImporter('.');
     var importCache = ImportCache(
         importers: [NodeModulesImporter()],
-        loadPaths: globalResults!['load-path']);
+        loadPaths: globalResults!['load-path'],
+        logger: _DeprecationLogger(this));
 
     var entrypoints = [
       for (var argument in argResults!.rest)
@@ -126,3 +132,22 @@ abstract class Migrator extends Command<Map<Uri, String>> {
     }
   }
 }
+
+/// A silent logger that calls [Migrator.handleDeprecation] when it receives a
+/// deprecation warning
+class _DeprecationLogger implements Logger {
+  final Migrator migrator;
+
+  _DeprecationLogger(this.migrator);
+
+  @override
+  void debug(String message, SourceSpan span) {}
+
+  @override
+  void warn(String message,
+      {FileSpan? span, Trace? trace, bool deprecation = false}) {
+    if (deprecation) {
+      migrator.handleDeprecation(message, span);
+    }
+  }
+}

lib/src/migrators/media_logic.dart

@@ -0,0 +1,57 @@
+// Copyright 2022 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 'package:sass_api/sass_api.dart';
+import 'package:source_span/source_span.dart';
+
+import '../migration_visitor.dart';
+import '../migrator.dart';
+import '../patch.dart';
+
+/// Migrates deprecated `@media` query syntax to use interpolation.
+class MediaLogicMigrator extends Migrator {
+  final name = 'media-logic';
+  final description = r'Migrates deprecated `@media` query syntax.\n'
+      'See https://sass-lang.com/d/media-logic.';
+
+  /// For each stylesheet URL, the set of relevant spans that require migration.
+  final _expressionsToMigrate = <Uri, Set<FileSpan>>{};
+
+  @override
+  void handleDeprecation(String message, FileSpan? span) {
+    if (span == null) return;
+    if (!message.startsWith('Starting a @media query with ')) return;
+    _expressionsToMigrate.putIfAbsent(span.sourceUrl!, () => {}).add(span);
+  }
+
+  @override
+  Map<Uri, String> migrateFile(
+      ImportCache importCache, Stylesheet stylesheet, Importer importer) {
+    var visitor = _MediaLogicVisitor(
+        importCache, migrateDependencies, _expressionsToMigrate);
+    var result = visitor.run(stylesheet, importer);
+    missingDependencies.addAll(visitor.missingDependencies);
+    return result;
+  }
+}
+
+class _MediaLogicVisitor extends MigrationVisitor {
+  /// For each stylesheet URL, the set of relevant spans that require migration.
+  final Map<Uri, Set<FileSpan>> _expressionsToMigrate;
+
+  _MediaLogicVisitor(ImportCache importCache, bool migrateDependencies,
+      this._expressionsToMigrate)
+      : super(importCache, migrateDependencies);
+
+  @override
+  void beforePatch(Stylesheet node) {
+    var expressions = _expressionsToMigrate[node.span.sourceUrl] ?? {};
+    for (var expression in expressions) {
+      addPatch(Patch.insert(expression.start, '#{'));
+      addPatch(Patch.insert(expression.end, '}'));
+    }
+  }
+}

lib/src/runner.dart

@@ -14,6 +14,7 @@ import 'package:term_glyph/term_glyph.dart' as glyph;
 
 import 'io.dart';
 import 'migrators/division.dart';
+import 'migrators/media_logic.dart';
 import 'migrators/module.dart';
 import 'migrators/namespace.dart';
 import 'migrators/strict_unary.dart';
@@ -54,6 +55,7 @@ class MigratorRunner extends CommandRunner<Map<Uri, String>> {
       ..addFlag('version',
           help: 'Print the version of the Sass migrator.', negatable: false);
     addCommand(DivisionMigrator());
+    addCommand(MediaLogicMigrator());
     addCommand(ModuleMigrator());
     addCommand(NamespaceMigrator());
     addCommand(StrictUnaryMigrator());

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass_migrator
-version: 1.6.0
+version: 1.7.0
 description: A tool for running migrations on Sass files
 homepage: https://github.com/sass/migrator
 
@@ -17,8 +17,9 @@ dependencies:
   node_interop: ^2.0.2
   node_io: ^2.2.0
   path: ^1.8.0
-  sass_api: ^3.0.0
+  sass_api: ^3.0.4
   source_span: ^1.8.1
+  stack_trace: ^1.10.0
   string_scanner: ^1.1.0
   term_glyph: ^1.2.0
   tuple: ^2.0.0

test/migrators/README.md

@@ -1,33 +1,10 @@
 # Migration Tests
 
-Each migrator should have:
+Each migrator should have a directory `<migrator-name>` that contains that
+migrator's HRX tests.
 
-* A `<migrator-name>_dart_test.dart` file that looks like:
-
-  ```dart
-  import '../utils.dart';
-
-  main() {
-    testMigrator("<migrator-name>");
-  }
-  ```
-
-* A `<migrator-name>_node_test.dart` file that looks like:
-
-  ```dart
-  @Tags("node")
-
-  import 'package:test/test.dart';
-
-  import '../utils.dart';
-
-  main() {
-    runNodeTests = true;
-    testMigrator("<migrator-name>");
-  }
-  ```
-
-* A directory `<migrator-name>` that contains that migrator's HRX tests,
+A line `testMigrator(<migrator-name>)` should then be added to the `main`
+function of `migrator_dart_test.dart`.
 
 ## HRX Format
 

test/migrators/media_logic/add_interpolation.hrx

@@ -0,0 +1,25 @@
+<==> input/entrypoint.scss
+@media (not (foo)) {
+  a {b: c}
+}
+
+@media ((foo) and (bar)) {
+  d {e: f}
+}
+
+@media ((foo) or (bar)) {
+  g {h: i}
+}
+
+<==> output/entrypoint.scss
+@media (#{not (foo)}) {
+  a {b: c}
+}
+
+@media (#{(foo) and (bar)}) {
+  d {e: f}
+}
+
+@media (#{(foo) or (bar)}) {
+  g {h: i}
+}

test/migrators/strict_unary_dart_test.dart → test/migrators/migrator_dart_test.dart

@@ -7,5 +7,9 @@
 import '../utils.dart';
 
 main() {
+  testMigrator("division");
+  testMigrator("media_logic");
+  testMigrator("module");
+  testMigrator("namespace");
   testMigrator("strict_unary");
 }

test/migrators/strict_unary_node_test.dart → test/migrators/migrator_node_test.dart

@@ -8,9 +8,10 @@
 
 import 'package:test/test.dart';
 
+import 'migrator_dart_test.dart' as dart;
 import '../utils.dart';
 
 main() {
   runNodeTests = true;
-  testMigrator("strict_unary");
+  dart.main();
 }