fix: do not generate classes if inputs are empty

This commit brings back behaviour from previous, kapt implementation, of not generating classes if inputs for them are empty.

This solves the problem of generating classes with empty content in different sourceset, e.g. `androidTest`. You can reproduce such problem in 80a80aa

Author: wzieba

libs/processors/src/main/java/org/wordpress/android/processor/RemoteConfigProcessor.kt

@@ -62,12 +62,14 @@ class RemoteConfigProcessor(
             }.flatMap { it.toList() }
             .toMap()
 
-        RemoteFeatureConfigDefaultsBuilder(defaults).getContent()
-            .writeTo(
-                codeGenerator,
-                aggregating = true,
-                originatingKSFiles = remoteFeatures.map { it.containingFile!! }
-            )
+        if (defaults.isNotEmpty()) {
+            RemoteFeatureConfigDefaultsBuilder(defaults).getContent()
+                .writeTo(
+                    codeGenerator,
+                    aggregating = true,
+                    originatingKSFiles = remoteFeatures.map { it.containingFile!! }
+                )
+        }
     }
 
     private fun generateRemoteFieldsConfigDefaults(resolver: Resolver) {
@@ -84,12 +86,14 @@ class RemoteConfigProcessor(
                     }
             }
 
-        RemoteFieldConfigDefaultsBuilder(remoteFieldDefaults).getContent()
-            .writeTo(
-                codeGenerator,
-                aggregating = true,
-                originatingKSFiles = remoteFields.map { it.containingFile!! }
-            )
+        if(remoteFieldDefaults.isNotEmpty()) {
+            RemoteFieldConfigDefaultsBuilder(remoteFieldDefaults).getContent()
+                .writeTo(
+                    codeGenerator,
+                    aggregating = true,
+                    originatingKSFiles = remoteFields.map { it.containingFile!! }
+                )
+        }
     }
 
     private fun generateFeaturesInDevelopment(resolver: Resolver) {
@@ -100,21 +104,25 @@ class RemoteConfigProcessor(
         val featuresInDevelopmentDefaults = featuresInDevelopment
             .map { it.simpleName.asString() }
 
-        FeaturesInDevelopmentDefaultsBuilder(featuresInDevelopmentDefaults).getContent()
-            .writeTo(
-                codeGenerator,
-                aggregating = true,
-                originatingKSFiles = featuresInDevelopment.map { it.containingFile!! }
-            )
+        if(featuresInDevelopmentDefaults.isNotEmpty()) {
+            FeaturesInDevelopmentDefaultsBuilder(featuresInDevelopmentDefaults).getContent()
+                .writeTo(
+                    codeGenerator,
+                    aggregating = true,
+                    originatingKSFiles = featuresInDevelopment.map { it.containingFile!! }
+                )
+        }
     }
 
     private fun generateRemoteFeatureConfigCheck(remoteFeatures: List<KSAnnotated>) {
-        RemoteFeatureConfigCheckBuilder(
-            remoteFeatures.filterIsInstance<KSClassDeclaration>().map { it.asType(emptyList()).toTypeName() }
-        ).getContent().writeTo(
-            codeGenerator,
-            aggregating = true,
-            originatingKSFiles = remoteFeatures.map { it.containingFile!! }
-        )
+        if(remoteFeatures.isNotEmpty()) {
+            RemoteFeatureConfigCheckBuilder(
+                remoteFeatures.filterIsInstance<KSClassDeclaration>().map { it.asType(emptyList()).toTypeName() }
+            ).getContent().writeTo(
+                codeGenerator,
+                aggregating = true,
+                originatingKSFiles = remoteFeatures.map { it.containingFile!! }
+            )
+        }
     }
 }