Fix --fatal-deprecation adding obsolete ones

See also #2647

Author: halo

lib/src/deprecation.dart

@@ -224,7 +224,8 @@ enum Deprecation {
     var range = VersionRange(max: version, includeMax: true);
     return {
       for (var deprecation in Deprecation.values)
-        if (deprecation.deprecatedIn.andThen(range.allows) ?? false)
+        if ((deprecation.deprecatedIn.andThen(range.allows) ?? false) &&
+            (deprecation.obsoleteIn.andThen((v) => !range.allows(v)) ?? true))
           deprecation,
     };
   }

test/deprecations_test.dart

@@ -8,6 +8,7 @@ library;
 import 'package:test/test.dart';
 
 import 'package:sass/sass.dart';
+import 'package:pub_semver/pub_semver.dart';
 
 void main() {
   // Deprecated in all version of Dart Sass
@@ -151,6 +152,36 @@ void main() {
       );
     });
   });
+
+  group('Deprecation.forVersion', () {
+    test('includes deprecation if not obsolete', () {
+      final version = Version.parse('1.91.0');
+      final deprecations = Deprecation.forVersion(version);
+
+      expect(
+        deprecations,
+        contains(Deprecation.mixedDecls),
+        reason: 'mixed-decls is obsolete in 1.92, should be fatal at 1.91',
+      );
+    });
+
+    test('excludes obsolete deprecations', () {
+      final version = Version.parse('1.93.0');
+      final deprecations = Deprecation.forVersion(version);
+
+      expect(
+        deprecations,
+        isNot(contains(Deprecation.mixedDecls)),
+        reason: 'mixed-decls is obsolete in 1.92, should not be fatal at 1.93',
+      );
+
+      expect(
+        deprecations,
+        contains(Deprecation.functionUnits),
+        reason: 'functionUnits is deprecated but not obsolete, should be fatal',
+      );
+    });
+  });
 }
 
 /// Confirms that [source] will error if [deprecation] is fatal.