Improve error message for factory to mention generated config

lib/src/builder/parsing/ast_util.dart

@@ -16,6 +16,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/syntactic_entity.dart';
 import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
+import 'package:over_react/src/builder/codegen/names.dart';
 import 'package:source_span/source_span.dart';
 import 'package:transformer_utils/transformer_utils.dart';
 
@@ -44,9 +45,10 @@ extension InitializerHelperTopLevel on TopLevelVariableDeclaration {
 
   /// Returns whether or not there is a generated config being used.
   bool get usesAGeneratedConfig {
+    final generatedConfigName = FactoryNames(firstVariable.name.name).configName;
     return firstInitializer != null &&
         anyDescendantIdentifiers(firstInitializer, (identifier) {
-          return identifier.nameWithoutPrefix == '\$${firstVariable.name.name}Config';
+          return identifier.nameWithoutPrefix == generatedConfigName;
         });
   }
 }

lib/src/builder/parsing/members.dart

@@ -14,6 +14,7 @@
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:meta/meta.dart';
+import 'package:over_react/src/builder/codegen/names.dart';
 import 'package:over_react/src/component_declaration/annotations.dart' as annotations;
 import 'package:over_react/src/util/pretty_print.dart';
 import 'package:over_react/src/util/string_util.dart';

lib/src/builder/parsing/members/factory.dart

@@ -84,7 +84,10 @@ class BoilerplateFactory extends BoilerplateMember {
 
     final variable = node.variables.variables.first;
     final factoryName = variable.name.name;
-    final generatedFactoryName = '$privateSourcePrefix$factoryName';
+
+    final names = FactoryNames(factoryName);
+    final generatedFactoryName = names.implName;
+    final generatedConfigName = names.configName;
 
     final initializer = variable.initializer;
     final referencesGeneratedFactory = initializer != null &&
@@ -93,8 +96,14 @@ class BoilerplateFactory extends BoilerplateMember {
 
     if (!referencesGeneratedFactory && !shouldGenerateConfig) {
       errorCollector.addError(
-          'Factory variables are stubs for the generated factories, and must '
-          'be initialized with or otherwise reference the generated factory. Should be: `$factoryName = $generatedFactoryName`',
+          'Factory variables are stubs for generated code, and must'
+          ' be initialized with an expression containing either '
+          ' the generated factory ($generatedFactoryName) or'
+          ' the generated factory config ($generatedConfigName).'
+          '\nExamples:'
+          '\n\n    $factoryName = $generatedFactoryName;'
+          '\n\n    $factoryName = connect(...)($generatedFactoryName);'
+          '\n\n    $factoryName = uiFunction((props) { ... }, $generatedConfigName);',
           errorCollector.spanFor(variable));
     }
   }