Refactor record shape processing out of calculating record bound fields

dwds/CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 19.0.1-dev
 
 - Do not show async frame errors on evaluation. - [#2073](https://github.com/dart-lang/webdev/pull/2073)
+- Refactor code for presenting record instances. - [#2074](https://github.com/dart-lang/webdev/pull/2074)
 
 ## 19.0.0
 

dwds/lib/src/debugging/instance.dart

@@ -446,52 +446,32 @@ class InstanceHelper extends Domain {
           .where((p) => p.name != null && int.tryParse(p.name!) != null)
           .toList();
 
-  /// The fields for a Dart Record.
+  /// The field names for a Dart record shape.
   ///
   /// Returns a range of [count] fields, if available, starting from
   /// the [offset].
   ///
   /// If [offset] is `null`, assumes 0 offset.
   /// If [count] is `null`, return all fields starting from the offset.
-  Future<List<BoundField>> _recordFields(
-    RemoteObject record, {
+  /// The [shape] object describes the shape using `positionalCount`
+  /// and `named` fields.
+  ///
+  /// Returns list of field names for the record shape.
+  Future<List<dynamic>> _recordShapeFields(
+    RemoteObject shape, {
     int? offset,
     int? count,
   }) async {
-    // We do this in in awkward way because we want the keys and values, but we
-    // can't return things by value or some Dart objects will come back as
-    // values that we need to be RemoteObject, e.g. a List of int.
-    final expression = '''
-      function() {
-        var sdkUtils = ${globalLoadStrategy.loadModuleSnippet}('dart_sdk').dart;
-        var shape = sdkUtils.dloadRepl(this, "shape");
-        var positionalCount = sdkUtils.dloadRepl(shape, "positionals");
-        var named = sdkUtils.dloadRepl(shape, "named");
-        named = named == null? null: sdkUtils.dsendRepl(named, "toList", []);
-        var values = sdkUtils.dloadRepl(this, "values");
-        values = sdkUtils.dsendRepl(values, "toList", []);
-
-        return {
-          positionalCount: positionalCount,
-          named: named,
-          values: values
-        };
-      }
-    ''';
-    final result = await inspector.jsCallFunctionOn(record, expression, []);
     final positionalCountObject =
-        await inspector.loadField(result, 'positionalCount');
+        await inspector.loadField(shape, 'positionalCount');
     if (positionalCountObject == null || positionalCountObject.value is! int) {
       _logger.warning(
         'Unexpected positional count from record: $positionalCountObject',
       );
       return [];
     }
 
-    final namedObject = await inspector.loadField(result, 'named');
-    final valuesObject = await inspector.loadField(result, 'values');
-
-    // Collect positional fields in the requested range.
+    final namedObject = await inspector.loadField(shape, 'named');
     final positionalCount = positionalCountObject.value as int;
     final positionalOffset = offset ?? 0;
     final positionalAvailable =
@@ -519,11 +499,49 @@ class InstanceHelper extends Domain {
     final namedElements =
         namedInstance?.elements?.map((e) => e.valueAsString) ?? [];
 
-    final fieldNameElements = [
+    return [
       ...positionalElements,
       ...namedElements,
     ];
+  }
+
+  /// The fields for a Dart Record.
+  ///
+  /// Returns a range of [count] fields, if available, starting from
+  /// the [offset].
+  ///
+  /// If [offset] is `null`, assumes 0 offset.
+  /// If [count] is `null`, return all fields starting from the offset.
+  Future<List<BoundField>> _recordFields(
+    RemoteObject record, {
+    int? offset,
+    int? count,
+  }) async {
+    // We do this in in awkward way because we want the keys and values, but we
+    // can't return things by value or some Dart objects will come back as
+    // values that we need to be RemoteObject, e.g. a List of int.
+    final expression = '''
+      function() {
+        var sdkUtils = ${globalLoadStrategy.loadModuleSnippet}('dart_sdk').dart;
+        var shape = sdkUtils.dloadRepl(this, "shape");
+        var positionalCount = sdkUtils.dloadRepl(shape, "positionals");
+        var named = sdkUtils.dloadRepl(shape, "named");
+        named = named == null? null: sdkUtils.dsendRepl(named, "toList", []);
+        var values = sdkUtils.dloadRepl(this, "values");
+        values = sdkUtils.dsendRepl(values, "toList", []);
+
+        return {
+          positionalCount: positionalCount,
+          named: named,
+          values: values
+        };
+      }
+    ''';
+    final result = await inspector.jsCallFunctionOn(record, expression, []);
+    final fieldNameElements =
+        await _recordShapeFields(result, offset: offset, count: count);
 
+    final valuesObject = await inspector.loadField(result, 'values');
     final valuesInstance =
         await instanceFor(valuesObject, offset: offset, count: count);
     final valueElements = valuesInstance?.elements ?? [];
@@ -533,11 +551,19 @@ class InstanceHelper extends Domain {
       return [];
     }
 
-    final fields = <BoundField>[];
-    Map.fromIterables(fieldNameElements, valueElements).forEach((key, value) {
-      fields.add(BoundField(name: key, value: value));
+    return _elementsToBoundFields(fieldNameElements, valueElements);
+  }
+
+  /// Create a list of `BoundField`s from field [names] and [values].
+  static List<BoundField> _elementsToBoundFields(
+    List<dynamic> names,
+    List<dynamic> values,
+  ) {
+    final boundFields = <BoundField>[];
+    Map.fromIterables(names, values).forEach((name, value) {
+      boundFields.add(BoundField(name: name, value: value));
     });
-    return fields;
+    return boundFields;
   }
 
   static int _remainingCount(int collected, int requested) {