Implement predefined field constraints (#178)

- Adds the ability to specify an `ExtensionRegistry` _and_ a
`TypeRegistry` for resolving protobuf messages. Ordinarily, only a
`TypeRegistry` would necessarily be needed. However, we need to be able
to resolve extensions defined in file descriptor sets we don't control,
which means we need to be able to reparse _to and from_ the user's
descriptors in the worst case: _to_ the user's descriptors to get the
extended rule message (whose message type descriptors may have a
different hashcode and thus may not resolve using just an
`ExtensionRegistry` alone) and back _from_ the user's descriptors in
order to parse the `priv`/`shared` field.
- Refactors some of the code around reparsing and extensions in general:
- Reparsing options for protovalidate built-ins will always use a static
extension registry.
- Adds the `rule` variable.
- Some refactoring is done around the individual rule compilation, since
the code was getting a bit unwieldy.
- Updates the conformance runner to generate an `ExtensionRegistry` and
a `TypeRegistry`. This enables the conformance runner to pass both the
old conformance test suite and the new one, regardless of whether the
proto descriptors match up.

TODO:
- [x] Update to new version of protovalidate protos when they are
merged.

This will depend on bufbuild/protovalidate#246.

Author: jchadwick-buf

conformance/src/main/java/build/buf/protovalidate/conformance/FileDescriptorUtil.java

@@ -16,6 +16,9 @@
 
 import com.google.protobuf.DescriptorProtos;
 import com.google.protobuf.Descriptors;
+import com.google.protobuf.DynamicMessage;
+import com.google.protobuf.ExtensionRegistry;
+import com.google.protobuf.TypeRegistry;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
@@ -70,4 +73,50 @@ static Map<String, Descriptors.FileDescriptor> parseFileDescriptors(
     }
     return fileDescriptorMap;
   }
+
+  static TypeRegistry createTypeRegistry(
+      Iterable<? extends Descriptors.FileDescriptor> fileDescriptors) {
+    TypeRegistry.Builder registryBuilder = TypeRegistry.newBuilder();
+    for (Descriptors.FileDescriptor fileDescriptor : fileDescriptors) {
+      registryBuilder.add(fileDescriptor.getMessageTypes());
+    }
+    return registryBuilder.build();
+  }
+
+  static ExtensionRegistry createExtensionRegistry(
+      Iterable<? extends Descriptors.FileDescriptor> fileDescriptors) {
+    ExtensionRegistry registry = ExtensionRegistry.newInstance();
+    for (Descriptors.FileDescriptor fileDescriptor : fileDescriptors) {
+      registerFileExtensions(registry, fileDescriptor);
+    }
+    return registry;
+  }
+
+  private static void registerFileExtensions(
+      ExtensionRegistry registry, Descriptors.FileDescriptor fileDescriptor) {
+    registerExtensions(registry, fileDescriptor.getExtensions());
+    for (Descriptors.Descriptor descriptor : fileDescriptor.getMessageTypes()) {
+      registerMessageExtensions(registry, descriptor);
+    }
+  }
+
+  private static void registerMessageExtensions(
+      ExtensionRegistry registry, Descriptors.Descriptor descriptor) {
+    registerExtensions(registry, descriptor.getExtensions());
+    for (Descriptors.Descriptor nestedDescriptor : descriptor.getNestedTypes()) {
+      registerMessageExtensions(registry, nestedDescriptor);
+    }
+  }
+
+  private static void registerExtensions(
+      ExtensionRegistry registry, List<Descriptors.FieldDescriptor> extensions) {
+    for (Descriptors.FieldDescriptor fieldDescriptor : extensions) {
+      if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
+        registry.add(
+            fieldDescriptor, DynamicMessage.getDefaultInstance(fieldDescriptor.getMessageType()));
+      } else {
+        registry.add(fieldDescriptor);
+      }
+    }
+  }
 }

conformance/src/main/java/build/buf/protovalidate/conformance/Main.java

@@ -33,6 +33,7 @@
 import com.google.protobuf.DynamicMessage;
 import com.google.protobuf.ExtensionRegistry;
 import com.google.protobuf.InvalidProtocolBufferException;
+import com.google.protobuf.TypeRegistry;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -57,7 +58,17 @@ static TestConformanceResponse testConformance(TestConformanceRequest request) {
     try {
       Map<String, Descriptors.Descriptor> descriptorMap =
           FileDescriptorUtil.parse(request.getFdset());
-      Validator validator = new Validator(Config.newBuilder().build());
+      Map<String, Descriptors.FileDescriptor> fileDescriptorMap =
+          FileDescriptorUtil.parseFileDescriptors(request.getFdset());
+      TypeRegistry typeRegistry = FileDescriptorUtil.createTypeRegistry(fileDescriptorMap.values());
+      ExtensionRegistry extensionRegistry =
+          FileDescriptorUtil.createExtensionRegistry(fileDescriptorMap.values());
+      Validator validator =
+          new Validator(
+              Config.newBuilder()
+                  .setTypeRegistry(typeRegistry)
+                  .setExtensionRegistry(extensionRegistry)
+                  .build());
       TestConformanceResponse.Builder responseBuilder = TestConformanceResponse.newBuilder();
       Map<String, TestResult> resultsMap = new HashMap<>();
       for (Map.Entry<String, Any> entry : request.getCasesMap().entrySet()) {