Support ConstructorElement (#1183)

Author: AlexV525

json_serializable/CHANGELOG.md

@@ -1,5 +1,7 @@
 ## 6.4.2-dev
 
+- Support `ConstructorElement` which allows using tear-off constructors.
+
 ## 6.4.1
 
 - Fixed a bug when an `@JsonSerializable` class uses a mixin with fields.

json_serializable/lib/src/utils.dart

@@ -232,6 +232,14 @@ extension ExecutableElementExtension on ExecutableElement {
       return '${enclosingElement3.name}.$name';
     }
 
+    if (this is ConstructorElement) {
+      // Ignore the default constructor.
+      if (name.isEmpty) {
+        return '${enclosingElement3.name}';
+      }
+      return '${enclosingElement3.name}.$name';
+    }
+
     throw UnsupportedError(
       'Not sure how to support typeof $runtimeType',
     );

json_serializable/test/json_serializable_test.dart

@@ -126,6 +126,7 @@ const _expectedAnnotatedTests = {
   'SubTypeWithAnnotatedFieldOverrideExtendsWithOverrides',
   'SubTypeWithAnnotatedFieldOverrideImplements',
   'theAnswer',
+  'TearOffFromJsonClass',
   'ToJsonNullableFalseIncludeIfNullFalse',
   'TypedConvertMethods',
   'UnknownEnumValue',

json_serializable/test/src/_json_serializable_test_input.dart

@@ -579,3 +579,31 @@ class Issue1038RegressionTest {
 
   Issue1038RegressionTest.ean(this.ean) : id = null;
 }
+
+@ShouldGenerate(
+  r'''
+TearOffFromJsonClass _$TearOffFromJsonClassFromJson(
+        Map<String, dynamic> json) =>
+    TearOffFromJsonClass(
+      TearOffValueClass(json['value'] as String),
+      TearOffValueClass.fromJson(json['factoryValue'] as String),
+    );
+''',
+)
+@JsonSerializable(createToJson: false)
+class TearOffFromJsonClass {
+  TearOffFromJsonClass(this.value, this.factoryValue);
+
+  @JsonKey(fromJson: TearOffValueClass.new)
+  final TearOffValueClass value;
+  @JsonKey(fromJson: TearOffValueClass.fromJson)
+  final TearOffValueClass factoryValue;
+}
+
+class TearOffValueClass {
+  const TearOffValueClass(this.value);
+
+  factory TearOffValueClass.fromJson(String value) => TearOffValueClass(value);
+
+  final String value;
+}