Fix typing and datetime imports not being present for service method type annotations (#183)

tests/inputs/config.py

@@ -14,6 +14,7 @@ services = {
     "googletypes_response",
     "googletypes_response_embedded",
     "service",
+    "service_separate_packages",
     "import_service_input_message",
     "googletypes_service_returns_empty",
     "googletypes_service_returns_googletype",

tests/inputs/service_separate_packages/messages.proto

@@ -0,0 +1,31 @@
+syntax = "proto3";
+
+import "google/protobuf/duration.proto";
+import "google/protobuf/timestamp.proto";
+
+package things.messages;
+
+message DoThingRequest {
+  string name = 1;
+
+  // use `repeated` so we can check if `List` is correctly imported
+  repeated string comments = 2;
+
+  // use google types `timestamp` and `duration` so we can check
+  // if everything from `datetime` is correctly imported
+  google.protobuf.Timestamp when = 3;
+  google.protobuf.Duration duration = 4;
+}
+
+message DoThingResponse {
+  repeated string names = 1;
+}
+
+message GetThingRequest {
+  string name = 1;
+}
+
+message GetThingResponse {
+  string name = 1;
+  int32 version = 2;
+}

tests/inputs/service_separate_packages/service.proto

@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+import "messages.proto";
+
+package things.service;
+
+service Test {
+  rpc DoThing (things.messages.DoThingRequest) returns (things.messages.DoThingResponse);
+  rpc DoManyThings (stream things.messages.DoThingRequest) returns (things.messages.DoThingResponse);
+  rpc GetThingVersions (things.messages.GetThingRequest) returns (stream things.messages.GetThingResponse);
+  rpc GetDifferentThings (stream things.messages.GetThingRequest) returns (stream things.messages.GetThingResponse);
+}