added optional associatedElement param to InvalidGenerationSourceError

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 0.8.1
+
+* `InvalidGenerationSourceError` added an optional `element`
+  parameter to support more helpful error messages.
+
 ## 0.8.0
 
 * **BREAKING** removed the deprecated `requireLibraryDirective` parameter in

lib/src/generator.dart

@@ -4,9 +4,11 @@
 
 import 'dart:async';
 
+import 'package:analyzer/dart/element/element.dart';
 import 'package:build/build.dart';
 
 import 'library.dart';
+import 'span_for_element.dart';
 
 /// A tool to generate Dart code based on a Dart library source.
 ///
@@ -36,9 +38,25 @@ class InvalidGenerationSourceError extends Error {
   /// May be an empty string if unknown.
   final String todo;
 
-  InvalidGenerationSourceError(this.message, {String todo})
+  /// The code element associated with this error.
+  ///
+  /// May be `null` if the error had no associated element.
+  final Element element;
+
+  InvalidGenerationSourceError(this.message, {String todo, this.element})
       : this.todo = todo ?? '';
 
   @override
-  String toString() => message;
+  String toString() {
+    var buffer = new StringBuffer(message);
+
+    if (element != null) {
+      var span = spanForElement(element);
+      buffer.writeln();
+      buffer.writeln(span.start.toolString);
+      buffer.write(span.highlight());
+    }
+
+    return buffer.toString();
+  }
 }

pubspec.yaml

@@ -1,5 +1,5 @@
 name: source_gen
-version: 0.8.0
+version: 0.8.1-dev
 author: Dart Team <misc@dartlang.org>
 description: Automated source code generation for Dart.
 homepage: https://github.com/dart-lang/source_gen

test/builder_test.dart

@@ -343,6 +343,9 @@ part of test_lib;
 // **************************************************************************
 
 // Error: Don't use classes with the word 'Error' in the name
+//        package:pkg/test_lib.dart:4:7
+//        class MyGoodError { }
+//              ^^^^^^^^^^^
 // TODO: Rename MyGoodError to something else.
 ''';
 

test/src/comment_generator.dart

@@ -29,7 +29,8 @@ class CommentGenerator extends Generator {
         if (classElement.displayName.contains('GoodError')) {
           throw new InvalidGenerationSourceError(
               "Don't use classes with the word 'Error' in the name",
-              todo: 'Rename ${classElement.displayName} to something else.');
+              todo: 'Rename ${classElement.displayName} to something else.',
+              element: classElement);
         }
         output.writeln('// Code for "$classElement"');
       }