Don't build symbols we already have in the state

lib/grpc_reflection/service/builder.ex

@@ -91,7 +91,7 @@ defmodule GrpcReflection.Service.Builder do
         symbol: Enum.find(fields, fn f -> f.name == name end).type_name
       }
     end)
-    |> Enum.reject(fn %{symbol: s} -> s == nil end)
+    |> Enum.reject(fn %{symbol: s} -> is_nil(s) or State.has_symbol?(state, s) end)
     |> Enum.reduce(state, fn %{mod: mod, symbol: symbol}, state ->
       symbol = Util.trim_symbol(symbol)
 

priv/protos/recursive_message.proto

@@ -0,0 +1,15 @@
+syntax = "proto3";
+
+package recursive_message;
+
+service Service {
+  rpc call (Request) returns (Reply) {}
+}
+
+message Request {
+  Reply reply = 1;
+}
+
+message Reply {
+  Request request = 1;
+}

test/service/builder_test.exs

@@ -140,4 +140,20 @@ defmodule GrpcReflection.Service.BuilderTest do
     assert {:ok, tree} = Builder.build_reflection_tree([WrappedService])
     assert %State{services: [WrappedService]} = tree
   end
+
+  test "handles a recursive message structure" do
+    assert {:ok, tree} = Builder.build_reflection_tree([RecursiveMessage.Service.Service])
+
+    assert tree.files |> Map.keys() |> Enum.sort() == [
+             "recursive_message.Reply.proto",
+             "recursive_message.Service.proto"
+           ]
+
+    assert tree.symbols |> Map.keys() |> Enum.sort() == [
+             "recursive_message.Reply",
+             "recursive_message.Request",
+             "recursive_message.Service",
+             "recursive_message.Service.call"
+           ]
+  end
 end

test/support/protos/recursive_message.pb.ex

@@ -0,0 +1,120 @@
+defmodule RecursiveMessage.Request do
+  @moduledoc false
+
+  use Protobuf, protoc_gen_elixir_version: "0.14.1", syntax: :proto3
+
+  def descriptor do
+    # credo:disable-for-next-line
+    %Google.Protobuf.DescriptorProto{
+      name: "Request",
+      field: [
+        %Google.Protobuf.FieldDescriptorProto{
+          name: "reply",
+          extendee: nil,
+          number: 1,
+          label: :LABEL_OPTIONAL,
+          type: :TYPE_MESSAGE,
+          type_name: ".recursive_message.Reply",
+          default_value: nil,
+          options: nil,
+          oneof_index: nil,
+          json_name: "reply",
+          proto3_optional: nil,
+          __unknown_fields__: []
+        }
+      ],
+      nested_type: [],
+      enum_type: [],
+      extension_range: [],
+      extension: [],
+      options: nil,
+      oneof_decl: [],
+      reserved_range: [],
+      reserved_name: [],
+      __unknown_fields__: []
+    }
+  end
+
+  field :reply, 1, type: RecursiveMessage.Reply
+end
+
+defmodule RecursiveMessage.Reply do
+  @moduledoc false
+
+  use Protobuf, protoc_gen_elixir_version: "0.14.1", syntax: :proto3
+
+  def descriptor do
+    # credo:disable-for-next-line
+    %Google.Protobuf.DescriptorProto{
+      name: "Reply",
+      field: [
+        %Google.Protobuf.FieldDescriptorProto{
+          name: "request",
+          extendee: nil,
+          number: 1,
+          label: :LABEL_OPTIONAL,
+          type: :TYPE_MESSAGE,
+          type_name: ".recursive_message.Request",
+          default_value: nil,
+          options: nil,
+          oneof_index: nil,
+          json_name: "request",
+          proto3_optional: nil,
+          __unknown_fields__: []
+        }
+      ],
+      nested_type: [],
+      enum_type: [],
+      extension_range: [],
+      extension: [],
+      options: nil,
+      oneof_decl: [],
+      reserved_range: [],
+      reserved_name: [],
+      __unknown_fields__: []
+    }
+  end
+
+  field :request, 1, type: RecursiveMessage.Request
+end
+
+defmodule RecursiveMessage.Service.Service do
+  @moduledoc false
+
+  use GRPC.Service, name: "recursive_message.Service", protoc_gen_elixir_version: "0.14.1"
+
+  def descriptor do
+    # credo:disable-for-next-line
+    %Google.Protobuf.ServiceDescriptorProto{
+      name: "Service",
+      method: [
+        %Google.Protobuf.MethodDescriptorProto{
+          name: "call",
+          input_type: ".recursive_message.Request",
+          output_type: ".recursive_message.Reply",
+          options: %Google.Protobuf.MethodOptions{
+            deprecated: false,
+            idempotency_level: :IDEMPOTENCY_UNKNOWN,
+            features: nil,
+            uninterpreted_option: [],
+            __pb_extensions__: %{},
+            __unknown_fields__: []
+          },
+          client_streaming: false,
+          server_streaming: false,
+          __unknown_fields__: []
+        }
+      ],
+      options: nil,
+      __unknown_fields__: []
+    }
+  end
+
+  rpc :call, RecursiveMessage.Request, RecursiveMessage.Reply
+end
+
+defmodule RecursiveMessage.Service.Stub do
+  @moduledoc false
+
+  use GRPC.Stub, service: RecursiveMessage.Service.Service
+end