Adding error return patterns to functions specs

.dialyzer-ignore.exs

@@ -0,0 +1,3 @@
+[
+  {":0:unknown_type Unknown type: Mongo.WriteError.t/0." }
+]

lib/mongo.ex

@@ -167,7 +167,8 @@ defmodule Mongo do
     * `:max_time` - Specifies a time limit in milliseconds
     * `:use_cursor` - Use a cursor for a batched response (Default: true)
   """
-  @spec aggregate(GenServer.server(), collection, [BSON.document()], Keyword.t()) :: cursor
+  @spec aggregate(GenServer.server(), collection, [BSON.document()], Keyword.t()) ::
+          cursor | {:error, Mongo.Error.t()}
   def aggregate(topology_pid, coll, pipeline, opts \\ []) do
     query =
       [
@@ -482,7 +483,8 @@ defmodule Mongo do
     * `:projection` - Limits the fields to return for all matching document
     * `:skip` - The number of documents to skip before returning (Default: 0)
   """
-  @spec find(GenServer.server(), collection, BSON.document(), Keyword.t()) :: cursor
+  @spec find(GenServer.server(), collection, BSON.document(), Keyword.t()) ::
+          cursor | {:error, Mongo.Error.t()}
   def find(topology_pid, coll, filter, opts \\ []) do
     query =
       [
@@ -538,7 +540,7 @@ defmodule Mongo do
     * `:skip` - The number of documents to skip before returning (Default: 0)
   """
   @spec find_one(GenServer.server(), collection, BSON.document(), Keyword.t()) ::
-          BSON.document() | nil
+          BSON.document() | nil | {:error, Mongo.Error.t()}
   def find_one(conn, coll, filter, opts \\ []) do
     opts =
       opts
@@ -597,10 +599,10 @@ defmodule Mongo do
     rp = ReadPreference.defaults(%{mode: :primary})
     rp_opts = [read_preference: Keyword.get(opts, :read_preference, rp)]
 
-     with {:ok, conn, slave_ok, _} <- select_server(topology_pid, :read, rp_opts) do
-       opts = Keyword.put(opts, :slave_ok, slave_ok)
-       direct_command(conn, query, opts)
-     end
+    with {:ok, conn, slave_ok, _} <- select_server(topology_pid, :read, rp_opts) do
+      opts = Keyword.put(opts, :slave_ok, slave_ok)
+      direct_command(conn, query, opts)
+    end
   end
 
   @doc false
@@ -1001,7 +1003,8 @@ defmodule Mongo do
   @doc """
   Returns a cursor to enumerate all indexes
   """
-  @spec list_indexes(GenServer.server(), String.t(), Keyword.t()) :: cursor
+  @spec list_indexes(GenServer.server(), String.t(), Keyword.t()) ::
+          cursor | {:error, Mongo.Error.t()}
   def list_indexes(topology_pid, coll, opts \\ []) do
     with {:ok, conn, _, _} <- select_server(topology_pid, :read, opts) do
       aggregation_cursor(conn, "$cmd", [listIndexes: coll], nil, opts)
@@ -1011,7 +1014,8 @@ defmodule Mongo do
   @doc """
   Convenient function that returns a cursor with the names of the indexes.
   """
-  @spec list_index_names(GenServer.server(), String.t(), Keyword.t()) :: %Stream{}
+  @spec list_index_names(GenServer.server(), String.t(), Keyword.t()) ::
+          %Stream{} | {:error, Mongo.Error.t()}
   def list_index_names(topology_pid, coll, opts \\ []) do
     list_indexes(topology_pid, coll, opts)
     |> Stream.map(fn %{"name" => name} -> name end)
@@ -1020,7 +1024,7 @@ defmodule Mongo do
   @doc """
   Getting Collection Names
   """
-  @spec show_collections(GenServer.server(), Keyword.t()) :: cursor
+  @spec show_collections(GenServer.server(), Keyword.t()) :: cursor | {:error, Mongo.Error.t()}
   def show_collections(topology_pid, opts \\ []) do
     ##
     # from the specs
@@ -1095,7 +1099,8 @@ defmodule Mongo do
             select_servers(topology_pid, type, opts, start_time)
 
           {:error, :selection_timeout} ->
-            {:error, %Mongo.Error{type: :network, message: "Topology selection timeout", code: 89}}
+            {:error,
+             %Mongo.Error{type: :network, message: "Topology selection timeout", code: 89}}
         end
       else
         {:ok, servers, slave_ok, mongos?}

lib/mongo/session.ex

@@ -339,9 +339,10 @@ defmodule Mongo.Session do
   @impl :gen_statem
   # Abort all pending transactions if there any and end session itself.
   def terminate(_reason, state, %{pid: pid} = data) do
-    if state == :in_transaction do
-      _ = try_run_txn_command(data, :abortTransaction)
-    end
+    _ =
+      if state == :in_transaction do
+        try_run_txn_command(data, :abortTransaction)
+      end
 
     query = %{
       endSessions: [data.id]

mix.exs

@@ -15,6 +15,7 @@ defmodule Mongodb.Mixfile do
       description: description(),
       package: package(),
       dialyzer: [
+        ignore_warnings: ".dialyzer-ignore.exs",
         flags: [:underspecs, :unknown, :unmatched_returns],
         plt_add_apps: [:logger, :connection, :db_connection, :mix, :elixir, :ssl, :public_key],
         plt_add_deps: :transitive