Put missing replica? in ServerDescription.parse_hello_response/1 and …

…add test.

lib/mongo/server_description.ex

@@ -117,7 +117,8 @@ defmodule Mongo.ServerDescription do
       compression: map_compressors(hello_response["compression"]),
       read_only: hello_response["readOnly"] || false,
       logical_session_timeout: hello_response["logicalSessionTimeoutMinutes"] || 30,
-      supports_retryable_writes: supports_retryable_writes
+      supports_retryable_writes: supports_retryable_writes,
+      replica?: replica?(server_type)
     }
   end
 

test/mongo/topology_description_test.exs

@@ -137,4 +137,12 @@ defmodule Mongo.TopologyDescriptionTest do
 
     assert :single = TopologyDescription.get_type(opts)
   end
+
+  test "Set read_preference to :primaryPreferred when topology is single and server is replica set" do
+    assert {:ok, {_, opts}} = TopologyDescription.select_servers(single(), :read, [])
+    assert nil == Keyword.get(opts, :read_preference)
+
+    assert {:ok, {_, opts}} = TopologyDescription.select_servers(single_with_repl_set(), :read, [])
+    assert :primaryPreferred = Keyword.get(opts, :read_preference) |> Map.get(:mode)
+  end
 end

test/support/topology_test_data.ex

@@ -36,6 +36,41 @@ defmodule Mongo.TopologyTestData do
       }
     }
 
+  def single_with_repl_set(),
+    do: %{
+      set_name: nil,
+      type: :single,
+      compatibility_error: nil,
+      compatible: true,
+      local_threshold_ms: 15,
+      max_election_id: nil,
+      max_set_version: nil,
+      servers: %{
+        "localhost:27017" => %{
+          address: "localhost:27017",
+          arbiters: [],
+          election_id: nil,
+          error: nil,
+          hosts: [],
+          last_update_time: nil,
+          last_write_date: nil,
+          max_wire_version: 4,
+          me: nil,
+          min_wire_version: 0,
+          op_time: nil,
+          passives: [],
+          primary: nil,
+          round_trip_time: 44,
+          set_name: nil,
+          set_version: nil,
+          tag_set: %{},
+          type: :standalone,
+          compression: [],
+          replica?: true
+        }
+      }
+    }
+
   def sharded(),
     do: %{
       set_name: nil,