fix: add support for top-level protobuf enums

src/main/java/com/google/api/generator/gapic/model/Message.java

@@ -23,6 +23,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 import javax.annotation.Nullable;
 
 @AutoValue
@@ -33,6 +34,12 @@ public abstract class Message {
   // a specific field.
   public abstract ImmutableList<Field> fields();
 
+  // String :: number value map for enums.
+  // TODO(unsupported): Consider making enums a separate POJO. However, that would require
+  // passing in a map of Message and another map of Enum types, which is not needed for
+  // 99.99% of protobuf generation.
+  public abstract ImmutableMap<String, Integer> enumValues();
+
   public abstract TypeNode type();
 
   public abstract ImmutableMap<String, Field> fieldMap();
@@ -49,6 +56,10 @@ public abstract class Message {
 
   public abstract Builder toBuilder();
 
+  public boolean isEnum() {
+    return !enumValues().isEmpty();
+  }
+
   public boolean hasResource() {
     return resource() != null;
   }
@@ -66,7 +77,11 @@ public Field findAndUnwrapFirstRepeatedField() {
   }
 
   public static Builder builder() {
-    return new AutoValue_Message.Builder().setOuterNestedTypes(Collections.emptyList());
+    return new AutoValue_Message.Builder()
+        .setOuterNestedTypes(Collections.emptyList())
+        .setFields(Collections.emptyList())
+        .setFieldMap(Collections.emptyMap())
+        .setEnumValues(Collections.emptyMap());
   }
 
   @AutoValue.Builder
@@ -75,6 +90,15 @@ public abstract static class Builder {
 
     public abstract Builder setFields(List<Field> fields);
 
+    public Builder setEnumValues(List<String> names, List<Integer> numbers) {
+      return setEnumValues(
+          IntStream.range(0, names.size())
+              .boxed()
+              .collect(Collectors.toMap(i -> names.get(i), i -> numbers.get(i))));
+    }
+
+    public abstract Builder setEnumValues(Map<String, Integer> enumValues);
+
     public abstract Builder setType(TypeNode type);
 
     public abstract Builder setResource(ResourceName resource);
@@ -85,11 +109,20 @@ public abstract static class Builder {
 
     abstract ImmutableList<Field> fields();
 
+    abstract ImmutableMap<String, Integer> enumValues();
+
     abstract Message autoBuild();
 
     public Message build() {
-      setFieldMap(fields().stream().collect(Collectors.toMap(f -> f.name(), f -> f)));
-      return autoBuild();
+      Message message = autoBuild();
+      if (!message.fields().isEmpty()) {
+        message =
+            message
+                .toBuilder()
+                .setFieldMap(fields().stream().collect(Collectors.toMap(f -> f.name(), f -> f)))
+                .autoBuild();
+      }
+      return message;
     }
   }
 }

src/main/java/com/google/api/generator/gapic/protoparser/Parser.java

@@ -45,6 +45,8 @@
 import com.google.protobuf.DescriptorProtos.ServiceOptions;
 import com.google.protobuf.Descriptors.Descriptor;
 import com.google.protobuf.Descriptors.DescriptorValidationException;
+import com.google.protobuf.Descriptors.EnumDescriptor;
+import com.google.protobuf.Descriptors.EnumValueDescriptor;
 import com.google.protobuf.Descriptors.FieldDescriptor;
 import com.google.protobuf.Descriptors.FileDescriptor;
 import com.google.protobuf.Descriptors.MethodDescriptor;
@@ -121,6 +123,7 @@ public static GapicContext parse(CodeGeneratorRequest request) {
     // While this takes an extra pass through the protobufs, the extra time is relatively trivial
     // and is worth the larger reduced maintenance cost.
     Map<String, Message> messages = parseMessages(request, outputResourceReferencesSeen);
+
     Map<String, ResourceName> resourceNames = parseResourceNames(request);
     messages = updateResourceNamesInMessages(messages, resourceNames.values());
 
@@ -343,6 +346,20 @@ public static Map<String, Message> parseMessages(
     for (Descriptor messageDescriptor : fileDescriptor.getMessageTypes()) {
       messages.putAll(parseMessages(messageDescriptor, outputResourceReferencesSeen));
     }
+    // We treat enums as messages since we primarily care only about the type representation.
+    for (EnumDescriptor enumDescriptor : fileDescriptor.getEnumTypes()) {
+      String name = enumDescriptor.getName();
+      List<EnumValueDescriptor> valueDescriptors = enumDescriptor.getValues();
+      messages.put(
+          name,
+          Message.builder()
+              .setType(TypeParser.parseType(enumDescriptor))
+              .setName(name)
+              .setEnumValues(
+                  valueDescriptors.stream().map(v -> v.getName()).collect(Collectors.toList()),
+                  valueDescriptors.stream().map(v -> v.getNumber()).collect(Collectors.toList()))
+              .build());
+    }
     return messages;
   }
 

src/main/java/com/google/api/generator/gapic/protoparser/TypeParser.java

@@ -89,6 +89,10 @@ public static TypeNode parseType(@Nonnull Descriptor messageDescriptor) {
     return TypeNode.withReference(parseMessageReference(messageDescriptor));
   }
 
+  public static TypeNode parseType(@Nonnull EnumDescriptor enumDescriptor) {
+    return TypeNode.withReference(parseEnumReference(enumDescriptor));
+  }
+
   public static String getPackage(FileDescriptor fileDescriptor) {
     String pakkage = fileDescriptor.getOptions().getJavaPackage();
     if (Strings.isNullOrEmpty(pakkage)) {
@@ -177,8 +181,29 @@ static Reference parseMessageReference(@Nonnull Descriptor messageDescriptor) {
   static Reference parseEnumReference(@Nonnull EnumDescriptor enumDescriptor) {
     // This is similar to parseMessageReference, but we make it a separate method because
     // EnumDescriptor and Descriptor are sibling types.
+    FileOptions fileOptions = enumDescriptor.getFile().getOptions();
+    String javaOuterClassname =
+        fileOptions.hasJavaOuterClassname() ? fileOptions.getJavaOuterClassname() : null;
+
+    // Some older protos don't have java_multiple_files option set, and don't have the outer
+    // classname option set either.
+    if (!fileOptions.getJavaMultipleFiles() && !fileOptions.hasJavaOuterClassname()) {
+      String fullFilePath = JavaStyle.toUpperCamelCase(enumDescriptor.getFile().getName());
+      javaOuterClassname =
+          JavaStyle.toUpperCamelCase(
+              fullFilePath.substring(
+                  fullFilePath.lastIndexOf("/") + 1, fullFilePath.lastIndexOf(".")));
+    }
+
+    boolean hasJavaOuterClass =
+        !Strings.isNullOrEmpty(javaOuterClassname) && !fileOptions.getJavaMultipleFiles();
     List<String> outerNestedTypeNames = new ArrayList<>();
+    if (hasJavaOuterClass) {
+      outerNestedTypeNames.add(javaOuterClassname);
+    }
+
     Descriptor containingType = enumDescriptor.getContainingType();
+
     // Handles nesting.
     while (containingType != null) {
       // Outermost type in the nested type hierarchy lies at index 0.
@@ -194,11 +219,18 @@ static Reference parseEnumReference(@Nonnull EnumDescriptor enumDescriptor) {
             .setEnclosingClassNames(outerNestedTypeNames)
             .build();
     String protoPackage = enumDescriptor.getFile().getPackage();
+    String enumFullName = enumDescriptor.getFullName();
+    if (hasJavaOuterClass) {
+      enumFullName =
+          String.format(
+              "%s.%s.%s",
+              enumFullName.substring(0, enumFullName.lastIndexOf(DOT)),
+              javaOuterClassname,
+              enumFullName.substring(enumFullName.lastIndexOf(DOT) + 1));
+    }
+
     Preconditions.checkState(
-        enumReference
-            .fullName()
-            .replace(pakkage, protoPackage)
-            .equals(enumDescriptor.getFullName()),
+        enumReference.fullName().replace(pakkage, protoPackage).equals(enumFullName),
         String.format(
             "Parsed enum name %s does not match actual name %s",
             enumReference.fullName().replace(pakkage, ""),

src/test/java/com/google/api/generator/gapic/composer/defaultvalue/DefaultValueComposerTest.java

@@ -20,7 +20,6 @@
 import com.google.api.generator.engine.ast.Expr;
 import com.google.api.generator.engine.ast.TypeNode;
 import com.google.api.generator.engine.writer.JavaWriterVisitor;
-import com.google.api.generator.gapic.composer.defaultvalue.DefaultValueComposer;
 import com.google.api.generator.gapic.model.Field;
 import com.google.api.generator.gapic.model.Message;
 import com.google.api.generator.gapic.model.ResourceName;
@@ -273,6 +272,7 @@ public void createSimpleMessage_containsMessagesEnumsAndResourceName() {
         "EchoRequest.newBuilder().setName("
             + "FoobarName.ofProjectFoobarName(\"[PROJECT]\", \"[FOOBAR]\").toString())"
             + ".setParent(FoobarName.ofProjectFoobarName(\"[PROJECT]\", \"[FOOBAR]\").toString())"
+            + ".setSeverity(Severity.forNumber(0))"
             + ".setFoobar(Foobar.newBuilder().build()).build()",
         writerVisitor.write());
   }

src/test/java/com/google/api/generator/gapic/composer/goldens/EchoClient.golden

@@ -314,6 +314,7 @@ public class EchoClient implements BackgroundResource {
    *       EchoRequest.newBuilder()
    *           .setName(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
    *           .setParent(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
+   *           .setSeverity(Severity.forNumber(0))
    *           .setFoobar(Foobar.newBuilder().build())
    *           .build();
    *   EchoResponse response = echoClient.echo(request);
@@ -337,6 +338,7 @@ public class EchoClient implements BackgroundResource {
    *       EchoRequest.newBuilder()
    *           .setName(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
    *           .setParent(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
+   *           .setSeverity(Severity.forNumber(0))
    *           .setFoobar(Foobar.newBuilder().build())
    *           .build();
    *   ApiFuture<EchoResponse> future = echoClient.echoCallable().futureCall(request);
@@ -397,6 +399,7 @@ public class EchoClient implements BackgroundResource {
    *       EchoRequest.newBuilder()
    *           .setName(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
    *           .setParent(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
+   *           .setSeverity(Severity.forNumber(0))
    *           .setFoobar(Foobar.newBuilder().build())
    *           .build();
    *   requestObserver.onNext(request);
@@ -418,6 +421,7 @@ public class EchoClient implements BackgroundResource {
    *       EchoRequest.newBuilder()
    *           .setName(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
    *           .setParent(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
+   *           .setSeverity(Severity.forNumber(0))
    *           .setFoobar(Foobar.newBuilder().build())
    *           .build();
    *   bidiStream.send(request);
@@ -442,6 +446,7 @@ public class EchoClient implements BackgroundResource {
    *       EchoRequest.newBuilder()
    *           .setName(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
    *           .setParent(FoobarName.ofProjectFoobarName("[PROJECT]", "[FOOBAR]").toString())
+   *           .setSeverity(Severity.forNumber(0))
    *           .setFoobar(Foobar.newBuilder().build())
    *           .build();
    *   bidiStream.send(request);