Issue #1130 added nest_all option to nest all parsed json into a _jso…

lib/plug/parsers/json.ex

@@ -21,6 +21,9 @@ defmodule Plug.Parsers.JSON do
 
   So by default, `Plug.Parsers` will read 1_000_000 bytes at a time from the
   socket with an overall limit of 8_000_000 bytes.
+
+  The option `:nest_all_json`, when true, specifies all parsed JSON (including maps)
+  are parsed into a `"_json"` key.
   """
 
   @behaviour Plug.Parsers
@@ -69,7 +72,7 @@ defmodule Plug.Parsers.JSON do
   @impl true
   def parse(conn, "application", subtype, _headers, {{mod, fun, args}, decoder, opts}) do
     if subtype == "json" or String.ends_with?(subtype, "+json") do
-      apply(mod, fun, [conn, opts | args]) |> decode(decoder)
+      apply(mod, fun, [conn, opts | args]) |> decode(decoder, opts)
     else
       {:next, conn}
     end
@@ -79,33 +82,35 @@ defmodule Plug.Parsers.JSON do
     {:next, conn}
   end
 
-  defp decode({:ok, "", conn}, _decoder) do
+  defp decode({:ok, "", conn}, _decoder, _opts) do
     {:ok, %{}, conn}
   end
 
-  defp decode({:ok, body, conn}, {module, fun, args}) do
+  defp decode({:ok, body, conn}, {module, fun, args}, opts) do
+    nest_all = Keyword.get(opts, :nest_all_json, false)
+
     try do
       apply(module, fun, [body | args])
     rescue
       e -> raise Plug.Parsers.ParseError, exception: e
     else
-      terms when is_map(terms) ->
+      terms when is_map(terms) and not nest_all ->
         {:ok, terms, conn}
 
       terms ->
         {:ok, %{"_json" => terms}, conn}
     end
   end
 
-  defp decode({:more, _, conn}, _decoder) do
+  defp decode({:more, _, conn}, _decoder, _opts) do
     {:error, :too_large, conn}
   end
 
-  defp decode({:error, :timeout}, _decoder) do
+  defp decode({:error, :timeout}, _decoder, _opts) do
     raise Plug.TimeoutError
   end
 
-  defp decode({:error, _}, _decoder) do
+  defp decode({:error, _}, _decoder, _opts) do
     raise Plug.BadRequestError
   end
 end

test/plug/parsers/json_test.exs

@@ -34,6 +34,14 @@ defmodule Plug.Parsers.JSONTest do
     def decode!(~s(null)) do
       nil
     end
+
+    def decode!("[]") do
+      []
+    end
+
+    def decode!("{_json: []}") do
+      %{"_json" => []}      
+    end
 
     def decode!(_) do
       raise "oops"
@@ -186,4 +194,11 @@ defmodule Plug.Parsers.JSONTest do
 
     assert Plug.Exception.status(exception) == 400
   end
+
+  test "nests all json when nest_all_json is true"  do
+    conn_object = "{_json: []}" |> json_conn() |> parse(nest_all_json: true)
+    conn_array = "[]" |> json_conn() |> parse(nest_all_json: true)
+    assert conn_object.params == %{"_json" => %{"_json" => []}}
+    assert conn_array.params == %{"_json" => []}
+  end
 end