type_url resolution fails when packing wrapper.proto messages into any.proto

[jackwootton]

I'm using wrapper.proto and packing various messages such as StringValue and Int32Value into any.proto. For example

from google.protobuf import wrappers_pb2
from google.protobuf import any_pb2

my_string_value = wrappers_pb2.StringValue(value='My String')
any = any_pb2.Any()
any.pack(my_string_value)

However, the ESP Proxy fails to resolve the type_url defined in message Any:

message Any {
  // A URL/resource name whose content describes the type of the
  // serialized protocol buffer message.
  //
  // For URLs which use the scheme `http`, `https`, or no scheme, the
  // following restrictions and interpretations apply:
  //
  // * If no scheme is provided, `https` is assumed.
  // * The last segment of the URL's path must represent the fully
  //   qualified name of the type (as in `path/google.protobuf.Duration`).
  //   The name should be in a canonical form (e.g., leading "." is
  //   not accepted).
  // * An HTTP GET on the URL must yield a [google.protobuf.Type][]
  //   value in binary format, or produce an error.
  // * Applications are allowed to cache lookup results based on the
  //   URL, or have them precompiled into a binary to avoid any
  //   lookup. Therefore, binary compatibility needs to be preserved
  //   on changes to types. (Use versioned type names to manage
  //   breaking changes.)
  //
  // Schemes other than `http`, `https` (or the empty scheme) might be
  // used with implementation specific semantics.
  //
  string type_url = 1;

  // Must be a valid serialized protocol buffer of the above specified type.
  bytes value = 2;
}

Instead, my client receives a 200 OK response of:

code: 13
details: [{@type: "type.googleapis.com/google.rpc.DebugInfo", stackEntries: [], detail: "internal"}]
message:"Type 'type.googleapis.com/google.protobuf.StringValue' cannot be found."

I'm testing this in a local ESP proxy. The following is the only message logged:

[libprotobuf WARNING external/protobuf_git/src/google/protobuf/util/internal/json_objectwriter.cc:53]
JsonObjectWriter was not fully closed.

[jackwootton]

If it helps, this is the file that marshals proto -> JSON

https://github.com/cloudendpoints/esp/blob/ee24633d0e6837f7d7fa05302f4ea6bd419a7d8e/src/api_manager/utils/marshalling.cc#L53