Fix bug in JS MultiSpan (#1801)

Fixes #1790.

CHANGELOG.md

@@ -5,6 +5,11 @@
 * Add an optional `argumentName` parameter to `SassScriptException()` to make it
   easier to throw exceptions associated with particular argument names.
 
+### JS API
+
+* Fix a bug in which certain warning spans would not have their properties
+  accessible by the JS API.
+
 ## 1.54.9
 
 * Fix an incorrect span in certain `@media` query deprecation warnings.

lib/src/node/source_span.dart

@@ -4,6 +4,7 @@
 
 import 'package:source_span/source_span.dart';
 
+import '../util/multi_span.dart';
 import '../util/nullable.dart';
 import 'reflection.dart';
 import 'utils.dart';
@@ -12,14 +13,17 @@ import 'utils.dart';
 /// that they match the JS API.
 void updateSourceSpanPrototype() {
   var span = SourceFile.fromString('').span(0);
+  var multiSpan = MultiSpan(span, '', {});
 
-  getJSClass(span).defineGetters({
+  for (var item in [span, multiSpan]) {
+    getJSClass(item).defineGetters({
       'start': (FileSpan span) => span.start,
       'end': (FileSpan span) => span.end,
       'url': (FileSpan span) => span.sourceUrl.andThen(dartToJSUrl),
       'text': (FileSpan span) => span.text,
       'context': (FileSpan span) => span.context,
     });
+  }
 
   // Offset is already accessible from JS because it's defined as a field rather
   // than a getter.

pubspec.yaml

@@ -1,5 +1,5 @@
 name: sass
-version: 1.55.0
+version: 1.55.0-dev
 description: A Sass implementation in Dart.
 homepage: https://github.com/sass/dart-sass