Preserve source-map extensions in SingleMapping (dart-archive/source_maps#31)

* Preserve source-map extensions in SingleMapping

* include test that extensions are preserved

Author: sigmundch

pkgs/source_maps/CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.10.8
+
+* Preserve source-map extensions in `SingleMapping`. Extensions are keys in the
+  json map that start with `"x_"`.
+
 ## 0.10.7
 
 * Set max SDK version to `<3.0.0`, and adjust other dependencies.

pkgs/source_maps/lib/parser.dart

@@ -278,8 +278,11 @@ class SingleMapping extends Mapping {
 
   final Uri _mapUrl;
 
+  final Map<String, dynamic> extensions;
+
   SingleMapping._(this.targetUrl, this.files, this.urls, this.names, this.lines)
-      : _mapUrl = null;
+      : _mapUrl = null,
+        extensions = {};
 
   factory SingleMapping.fromEntries(Iterable<builder.Entry> entries,
       [String fileUrl]) {
@@ -341,7 +344,8 @@ class SingleMapping extends Mapping {
         files = new List(map['sources'].length),
         sourceRoot = map['sourceRoot'],
         lines = <TargetLineEntry>[],
-        _mapUrl = mapUrl is String ? Uri.parse(mapUrl) : mapUrl {
+        _mapUrl = mapUrl is String ? Uri.parse(mapUrl) : mapUrl,
+        extensions = {} {
     var sourcesContent = map['sourcesContent'] == null
         ? const []
         : new List<String>.from(map['sourcesContent']);
@@ -414,6 +418,10 @@ class SingleMapping extends Mapping {
     if (!entries.isEmpty) {
       lines.add(new TargetLineEntry(line, entries));
     }
+
+    map.forEach((name, value) {
+      if (name.startsWith("x_")) extensions[name] = value;
+    });
   }
 
   /// Encodes the Mapping mappings as a json map.
@@ -471,6 +479,7 @@ class SingleMapping extends Mapping {
     if (includeSourceContents) {
       result['sourcesContent'] = files.map((file) => file?.getText(0)).toList();
     }
+    extensions.forEach((name, value) => result[name] = value);
 
     return result;
   }

pkgs/source_maps/pubspec.yaml

@@ -1,5 +1,5 @@
 name: source_maps
-version: 0.10.7
+version: 0.10.8
 
 description: Library to programmatically manipulate source map files.
 author: Dart Team <[email protected]>

pkgs/source_maps/test/parser_test.dart

@@ -342,6 +342,16 @@ main() {
     expect(mapping.toJson(), equals(SOURCE_MAP_BUNDLE));
   });
 
+  test('parse extensions', () {
+    var map = new Map.from(EXPECTED_MAP);
+    map["x_foo"] = "a";
+    map["x_bar"] = [3];
+    SingleMapping mapping = parseJson(map);
+    expect(mapping.toJson(), equals(map));
+    expect(mapping.extensions["x_foo"], equals("a"));
+    expect(mapping.extensions["x_bar"].first, equals(3));
+  });
+
   group("source files", () {
     group("from fromEntries()", () {
       test("are null for non-FileLocations", () {