Generator: more helpful error, test if ambiguous backlink source #130

Author: greenrobot-team

generator/lib/src/code_builder.dart

@@ -399,12 +399,19 @@ class CodeBuilder extends Builder {
     ModelRelation? srcRel;
     ModelProperty? srcProp;
 
-    throwAmbiguousError(String prop, String rel) =>
-        throw InvalidGenerationSourceError(
-          "Ambiguous relation backlink source for '${entity.name}.${bl.name}':"
-          " Found matching property '$prop' and to-many relation '$rel'."
-          " Maybe specify source name in @Backlink() annotation.",
-        );
+    throwAmbiguousError(
+      Iterable<ModelProperty> toOneProps,
+      Iterable<ModelRelation> toManyRels,
+    ) {
+      final toOneList = toOneProps.map((p) => p.relationField);
+      final toManyList = toManyRels.map((r) => r.name);
+      final fieldList = [...toOneList, ...toManyList].join(', ');
+      throw InvalidGenerationSourceError(
+        "Can't determine backlink source for \"${entity.name}.${bl.name}\" "
+        "as there is more than one matching ToOne or ToMany relation in \"${srcEntity.name}\": $fieldList."
+        " Add the name of the source relation to the annotation, like @Backlink('<source>'), or modify your entity classes.",
+      );
+    }
 
     if (bl.srcField.isEmpty) {
       final matchingProps = srcEntity.properties.where(
@@ -415,7 +422,7 @@ class CodeBuilder extends Builder {
       );
       final candidatesCount = matchingProps.length + matchingRels.length;
       if (candidatesCount > 1) {
-        throwAmbiguousError(matchingProps.toString(), matchingRels.toString());
+        throwAmbiguousError(matchingProps, matchingRels);
       } else if (matchingProps.isNotEmpty) {
         srcProp = matchingProps.first;
       } else if (matchingRels.isNotEmpty) {
@@ -428,7 +435,7 @@ class CodeBuilder extends Builder {
       );
 
       if (srcProp != null && srcRel != null) {
-        throwAmbiguousError(srcProp.toString(), srcRel.toString());
+        throwAmbiguousError([srcProp], [srcRel]);
       }
     }
 

generator/test/code_builder_test.dart

@@ -203,7 +203,7 @@ void main() {
         }
         ''';
 
-        final result = await testEnv.run(source, expectNoOutput: true);
+        final result = await testEnv.run(source, ignoreOutput: true);
 
         expect(result.builderResult.succeeded, false);
         expect(
@@ -324,6 +324,49 @@ void main() {
       );
     });
 
+    test('Errors if backlink source is not unique', () async {
+      final source = r'''
+      library example;     
+      import 'package:objectbox/objectbox.dart';
+      
+      @Entity()
+      class Example {
+        @Id()
+        int id = 0;
+        
+        final relA1 = ToOne<A>();
+        final relA2 = ToOne<A>();
+        final relA3 = ToMany<A>();
+      }
+       
+      @Entity()
+      class A {
+        @Id()
+        int id = 0;
+        
+        @Backlink()
+        final backRel = ToMany<Example>();
+      }
+      ''';
+
+      final testEnv = GeneratorTestEnv();
+      final result = await testEnv.run(source, ignoreOutput: true);
+
+      expect(result.builderResult.succeeded, false);
+      expect(
+        result.logs,
+        contains(
+          isA<LogRecord>()
+              .having((r) => r.level, 'level', Level.SEVERE)
+              .having(
+                (r) => r.message,
+                'message',
+                contains('Can\'t determine backlink source for "A.backRel"'),
+              ),
+        ),
+      );
+    });
+
     test('@TargetIdProperty ToOne annotation', () async {
       final source = r'''
       library example;     
@@ -368,7 +411,7 @@ void main() {
       ''';
 
       final testEnv = GeneratorTestEnv();
-      final result = await testEnv.run(source, expectNoOutput: true);
+      final result = await testEnv.run(source, ignoreOutput: true);
 
       expect(result.builderResult.succeeded, false);
       expect(
@@ -403,7 +446,7 @@ void main() {
       ''';
 
       final testEnv = GeneratorTestEnv();
-      final result = await testEnv.run(source, expectNoOutput: true);
+      final result = await testEnv.run(source, ignoreOutput: true);
 
       expect(result.builderResult.succeeded, false);
       expect(

generator/test/generator_test_env.dart

@@ -37,7 +37,7 @@ class GeneratorTestEnv {
 
   Future<GeneratorTestResult> run(
     String source, {
-    bool expectNoOutput = false,
+    bool ignoreOutput = false,
   }) async {
     final library = "example";
     // Enable resolving imports (imported packages must be a dependency of this package)
@@ -66,7 +66,7 @@ class GeneratorTestEnv {
       [resolver, codeBuilder],
       sourceAssets,
       readerWriter: readerWriter,
-      outputs: expectNoOutput ? {} : expectedOutputs,
+      outputs: ignoreOutput ? null : expectedOutputs,
       onLog: (record) {
         // Setting onLog overwrites the useful default logger set by
         // testBuilders, so reimplement it
@@ -76,7 +76,7 @@ class GeneratorTestEnv {
       },
     );
 
-    if (!expectNoOutput) {
+    if (!ignoreOutput) {
       // Assert generator model
       final modelFile = File(path.join("lib", config.jsonFile));
       final jsonModel = await _readModelFile(modelFile);