Support writing structured data directly, without JSON encoding

README.md

@@ -97,7 +97,7 @@ If it exists in your endpoint, replace it with this (using the options you
 want):
 
 ```elixir
-plug Uinta.Plug, json: false, log: :info
+plug Uinta.Plug, format: :string, log: :info
 ```
 
 You can also perform log sampling by setting the `success_log_sampling_ratio`. Following is a 20% log sampling

lib/uinta/plug.ex

@@ -44,7 +44,7 @@ if Code.ensure_loaded?(Plug) do
     ```
     plug Uinta.Plug,
       log: :info,
-      json: false,
+      format: :string,
       include_variables: false,
       ignored_paths: [],
       filter_variables: [],
@@ -70,8 +70,8 @@ if Code.ensure_loaded?(Plug) do
 
     - `:log` - The log level at which this plug should log its request info.
     Default is `:info`
-    - `:json` - Whether or not this plug should log in JSON format. Default is
-    `false`
+    - `:format` - Output format, either :json, :string, or :map. Default is `:string`
+    - `:json` - Whether or not plug should log in JSON format. Default is `false` (obsolete)
     - `:ignored_paths` - A list of paths that should not log requests. Default
     is `[]`.
     - `:include_variables` - Whether or not to include any GraphQL variables in
@@ -96,7 +96,7 @@ if Code.ensure_loaded?(Plug) do
 
     @query_name_regex ~r/^\s*(?:query|mutation)\s+(\w+)|{\W+(\w+)\W+?{/m
 
-    @type format :: :json | :string
+    @type format :: :json | :map | :string
     @type graphql_info :: %{type: String.t(), operation: String.t(), variables: String.t() | nil}
     @type opts :: %{
             level: Logger.level(),
@@ -110,7 +110,14 @@ if Code.ensure_loaded?(Plug) do
 
     @impl Plug
     def init(opts) do
-      format = if Keyword.get(opts, :json, false), do: :json, else: :string
+      format =
+        case Keyword.fetch(opts, :format) do
+          {:ok, value} when value in [:json, :map, :string] ->
+            value
+
+          :error ->
+            if Keyword.get(opts, :json, false), do: :json, else: :string
+        end
 
       %{
         level: Keyword.get(opts, :log, :info),
@@ -195,13 +202,13 @@ if Code.ensure_loaded?(Plug) do
       end
     end
 
-    @spec format_line(map(), format()) :: iodata()
+    @spec format_line(map(), format()) :: iodata() | map()
+    defp format_line(info, :map) do
+      format_info(info)
+    end
+
     defp format_line(info, :json) do
-      info =
-        info
-        |> Map.delete(:connection_type)
-        |> Enum.filter(fn {_, value} -> !is_nil(value) end)
-        |> Enum.into(%{})
+      info = format_info(info)
 
       case Jason.encode(info) do
         {:ok, encoded} -> encoded
@@ -217,6 +224,14 @@ if Code.ensure_loaded?(Plug) do
       if is_nil(info.query), do: log, else: [log, "\nQuery: ", info.query]
     end
 
+    # Format structured data for output
+    @spec format_info(map()) :: map()
+    defp format_info(info) do
+      info
+      |> Map.delete(:connection_type)
+      |> Map.reject(fn {_, value} -> is_nil(value) end)
+    end
+
     defp get_first_value_for_header(conn, name) do
       conn
       |> Plug.Conn.get_req_header(name)

test/uinta/plug_test.exs

@@ -28,6 +28,17 @@ defmodule Uinta.PlugTest do
     end
   end
 
+  defmodule MapPlug do
+    use Plug.Builder
+
+    plug(Uinta.Plug, format: :map)
+    plug(:passthrough)
+
+    defp passthrough(conn, _) do
+      Plug.Conn.send_resp(conn, 200, "Passthrough")
+    end
+  end
+
   defmodule JsonPlugWithDataDogFields do
     use Plug.Builder
 
@@ -162,6 +173,20 @@ defmodule Uinta.PlugTest do
     assert message =~ ~r"\[info\]\s+POST /hello/world - Sent 200 in [0-9]+[µm]s"u
   end
 
+  test "logs map to console" do
+    message =
+      capture_log(fn ->
+        MapPlug.call(conn(:get, "/"), [])
+      end)
+
+    assert message =~ ~r/client_ip: \"127.0.0.1\"/u
+    assert message =~ ~r/duration_ms: [0-9]+\.?[0-9]+/u
+    assert message =~ ~r/method: \"GET\"/u
+    assert message =~ ~r"path: \"/\""u
+    assert message =~ ~r/status: \"200\"/u
+    assert message =~ ~r/timing: \"[0-9]+[µm]s\"/u
+  end
+
   test "logs proper json to console" do
     message =
       capture_log(fn ->