Add support for fully generic classes. (firebase#1172)

Until now it was possible to annotate non-generic classes with `@Encodable`, while their properties could be generic with fully bound type variables. This change makes it possible to generate encoders for generic classes with generic properties, but with a compiler warning. Example: ```java @encodable public class GenericClass<T, U> { public T getT(); // warning generated public U getU(); // warning generated } ```

Author: vkryachko

encoders/firebase-encoders-processor/src/main/java/com/google/firebase/encoders/processor/getters/GetterFactory.java

@@ -142,6 +142,14 @@ private TypeMirror resolveTypeArguments(DeclaredType ownerType, TypeMirror gener
  genericType, ownerType));
  return genericType;
  }
+ if (ownerType.getTypeArguments().get(index) instanceof TypeVariable) {
+ messager.printMessage(
+ Diagnostic.Kind.WARNING,
+ String.format(
+ "%s is a generic type, make sure you register encoders for types of %s that you plan to use.",
+ ownerType, genericType));
+ return genericType;
+ }
  return resolveTypeArguments(ownerType, ownerType.getTypeArguments().get(index));
  }
  return genericType;

encoders/firebase-encoders-processor/src/test/java/com/google/firebase/encoders/processor/EncodableProcessorTest.java

@@ -115,6 +115,27 @@ public void compile_withNonStaticNestedInsideGenericClass_shouldFail() {
  assertThat(result).hadErrorContaining("Could not infer type");
  }
 
+ @Test
+ public void compile_withGenericClass_ShouldWarnAboutPotentialProblems() {
+ Compilation result =
+ javac()
+ .withProcessors(new EncodableProcessor())
+ .compile(
+ JavaFileObjects.forSourceLines(
+ "GenericClass",
+ "import com.google.firebase.encoders.annotations.Encodable;",
+ "@Encodable public class GenericClass<T, U> {",
+ "public T getT() { return null; }",
+ "public U getU() { return null; }",
+ "}"));
+
+ assertThat(result).hadWarningContaining("GenericClass<T,U> is a generic type");
+ assertThat(result)
+ .generatedSourceFile("AutoGenericClassEncoder")
+ .hasSourceEquivalentTo(
+ JavaFileObjects.forResource("ExpectedGenericsEncoderWithUnknownType.java"));
+ }
+
  @Test
  public void compile_withMultipleGenericArgs_shouldCreateEncodersForAllKnownGenericArgs() {
  Compilation result =

encoders/firebase-encoders-processor/src/test/resources/ExpectedGenericsEncoderWithUnknownType.java

@@ -0,0 +1,50 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import com.google.firebase.encoders.EncodingException;
+import com.google.firebase.encoders.ObjectEncoder;
+import com.google.firebase.encoders.ObjectEncoderContext;
+import com.google.firebase.encoders.config.Configurator;
+import com.google.firebase.encoders.config.EncoderConfig;
+import java.io.IOException;
+import java.lang.Override;
+import javax.annotation.Generated;
+
+/**
+ * @hide */
+@Generated("com.google.firebase.encoders.processor.EncodableProcessor")
+public final class AutoGenericClassEncoder implements Configurator {
+ public static final int CODEGEN_VERSION = 1;
+
+ public static final Configurator CONFIG = new AutoGenericClassEncoder();
+
+ private AutoGenericClassEncoder() {
+ }
+
+ @Override
+ public void configure(EncoderConfig<?> cfg) {
+ cfg.registerEncoder(GenericClass.class, GenericClassEncoder.INSTANCE);
+ }
+
+ private static final class GenericClassEncoder implements ObjectEncoder<GenericClass> {
+ static final GenericClassEncoder INSTANCE = new GenericClassEncoder();
+
+ @Override
+ public void encode(GenericClass value, ObjectEncoderContext ctx) throws IOException,
+ EncodingException {
+ ctx.add("t", value.getT());
+ ctx.add("u", value.getU());
+ }
+ }
+}