JAVA-2286: Improve error reporting when entity has no properties

tolbertam · olim7t · commit 984d64f34be0 · 2019-06-21T15:14:02.000-07:00
Motivation:

Currently if an Entity-annotated class lacks any properties, code
generation produces code that doesn't compile because no properties are
specified using QueryBuilder.

To rectify this, preemptively check to see if an Entity lacks properties
when generating its definition.

Modifications:

Update DefaultEntityFactory.getDefinition to generate an error if no
properties are specified on an Entity-annotated class.

Result:

A more appropriate compiler error is now generated informing the user
that their Entity-annotated class lacks properties.
diff --git a/mapper-processor/src/main/java/com/datastax/oss/driver/internal/mapper/processor/entity/DefaultEntityFactory.java b/mapper-processor/src/main/java/com/datastax/oss/driver/internal/mapper/processor/entity/DefaultEntityFactory.java
@@ -186,6 +186,15 @@ public EntityDefinition getDefinition(TypeElement classElement) {
       }
     }
 
+    if (encounteredPropertyNames.isEmpty()) {
+      context
+          .getMessager()
+          .error(
+              classElement,
+              "@%s-annotated class must have at least one property defined.",
+              Entity.class.getSimpleName());
+    }
+
     String entityName = Introspector.decapitalize(classElement.getSimpleName().toString());
     String defaultKeyspace = classElement.getAnnotation(Entity.class).defaultKeyspace();
 
diff --git a/mapper-processor/src/test/java/com/datastax/oss/driver/internal/mapper/processor/entity/EntityPropertyAnnotationsTest.java b/mapper-processor/src/test/java/com/datastax/oss/driver/internal/mapper/processor/entity/EntityPropertyAnnotationsTest.java
@@ -307,6 +307,19 @@ public static Object[][] entitiesWithErrors() {
                     .build())
             .build(),
       },
+      {
+        "@Entity-annotated class must have at least one property defined.",
+        TypeSpec.classBuilder(ClassName.get("test", "Product"))
+            .addAnnotation(Entity.class)
+            .addField(FieldSpec.builder(UUID.class, "id", Modifier.PRIVATE).build())
+            .addMethod(
+                MethodSpec.methodBuilder("getId")
+                    .returns(UUID.class)
+                    .addModifiers(Modifier.PUBLIC)
+                    .addStatement("return id")
+                    .build())
+            .build(),
+      },
     };
   }
 }

Original file line number	Diff line number	Diff line change
`@@ -186,6 +186,15 @@ public EntityDefinition getDefinition(TypeElement classElement) {`
`186`	`186`	`}`
`187`	`187`	`}`
`188`	`188`
	`189`	`+ if (encounteredPropertyNames.isEmpty()) {`
	`190`	`+ context`
	`191`	`+ .getMessager()`
	`192`	`+ .error(`
	`193`	`+ classElement,`
	`194`	`+ "@%s-annotated class must have at least one property defined.",`
	`195`	`+ Entity.class.getSimpleName());`
	`196`	`+ }`
	`197`	`+`
`189`	`198`	`String entityName = Introspector.decapitalize(classElement.getSimpleName().toString());`
`190`	`199`	`String defaultKeyspace = classElement.getAnnotation(Entity.class).defaultKeyspace();`
`191`	`200`