Implementation of multipart parsing for test adapter (#501)

lib/plug/adapters/test/conn.ex

@@ -86,8 +86,16 @@ defmodule Plug.Adapters.Test.Conn do
     {tag, data, %{state | req_body: rest}}
   end
 
-  def parse_req_multipart(%{params: multipart} = state, _limit, _callback) do
-    {:ok, multipart, %{state | params: nil}}
+  def parse_req_multipart(%{params: params} = state, _opts, _callback) do
+    {:ok, params, state}
+  end
+
+  def parse_req_multipart(%{req_body: multipart} = state, opts, callback) do
+    boundary = Keyword.get(opts, :boundary)
+    params = parse_multipart(:cow_multipart.parse_headers(multipart, boundary), boundary, [], callback)
+      |> Enum.reduce(%{}, &Plug.Conn.Query.decode_pair/2)
+
+    {:ok, params, state}
   end
 
   ## Private helpers
@@ -138,4 +146,27 @@ defmodule Plug.Adapters.Test.Conn do
       0 -> :ok
     end
   end
+
+  defp parse_multipart({:ok, headers, body}, boundary, acc, callback) do
+    {:done, content, rest} = :cow_multipart.parse_body(body, boundary)
+
+    case callback.(headers)do
+      {:file, name, path, %Plug.Upload{} = uploaded} ->
+        {:ok, file} = File.open(path, [:write, :binary, :delayed_write, :raw])
+        IO.binwrite(file, content)
+        File.close(file)
+
+        parse_multipart(:cow_multipart.parse_headers(rest, boundary), boundary, [{name, uploaded}|acc], callback)
+
+        {:binary, name} ->
+          parse_multipart(:cow_multipart.parse_headers(rest, boundary), boundary, [{name, content}|acc], callback)
+
+        :skip ->
+          parse_multipart(:cow_multipart.parse_headers(rest, boundary), boundary, acc, callback)
+    end
+  end
+
+  defp parse_multipart({:done, _rest}, _boundary, acc, _callback) do
+    acc
+  end
 end

lib/plug/parsers/multipart.ex

@@ -10,11 +10,11 @@ defmodule Plug.Parsers.MULTIPART do
 
   @behaviour Plug.Parsers
 
-  def parse(conn, "multipart", subtype, _headers, opts) when subtype in ["form-data", "mixed"] do
+  def parse(conn, "multipart", subtype, headers, opts) when subtype in ["form-data", "mixed"] do
     {adapter, state} = conn.adapter
 
     try do
-      adapter.parse_req_multipart(state, opts, &handle_headers/1)
+      adapter.parse_req_multipart(state, add_boundary(opts, Map.get(headers, "boundary")), &handle_headers/1)
     rescue
       e in Plug.UploadError -> # Do not ignore upload errors
         reraise e, System.stacktrace
@@ -36,7 +36,7 @@ defmodule Plug.Parsers.MULTIPART do
     {:next, conn}
   end
 
-  defp handle_headers(headers) do
+  def handle_headers(headers) do
     case List.keyfind(headers, "content-disposition", 0) do
       {_, disposition} -> handle_disposition(disposition, headers)
       nil -> :skip
@@ -74,4 +74,9 @@ defmodule Plug.Parsers.MULTIPART do
       nil -> nil
     end
   end
+
+  defp add_boundary(opts, nil), do: opts
+  defp add_boundary(opts, boundary) do
+    opts ++ [{:boundary, boundary}]
+  end
 end

test/plug/adapters/test/conn_test.exs

@@ -54,10 +54,52 @@ defmodule Plug.Adapters.Test.ConnTest do
   end
 
   test "parse_req_multipart/4" do
-    conn = conn(:get, "/", a: "b", c: [%{d: "e"}, "f"])
-    {adapter, state} = conn.adapter
-    assert {:ok, params, _} = adapter.parse_req_multipart(state, 1_000_000, fn _ -> :ok end)
-    assert params == %{"a" => "b", "c" => [%{"d" => "e"}, "f"]}
+    multipart = """
+    ------w58EW1cEpjzydSCq\r
+    Content-Disposition: form-data; name=\"name\"\r
+    \r
+    hello\r
+    ------w58EW1cEpjzydSCq\r
+    Content-Disposition: form-data; name=\"pic\"; filename=\"foo.txt\"\r
+    Content-Type: text/plain\r
+    \r
+    hello
+
+    \r
+    ------w58EW1cEpjzydSCq\r
+    Content-Disposition: form-data; name=\"empty\"; filename=\"\"\r
+    Content-Type: application/octet-stream\r
+    \r
+    \r
+    ------w58EW1cEpjzydSCq\r
+    Content-Disposition: form-data; name="status[]"\r
+    \r
+    choice1\r
+    ------w58EW1cEpjzydSCq\r
+    Content-Disposition: form-data; name="status[]"\r
+    \r
+    choice2\r
+    ------w58EW1cEpjzydSCq\r
+    Content-Disposition: form-data; name=\"commit\"\r
+    \r
+    Create User\r
+    ------w58EW1cEpjzydSCq--\r
+    """
+
+    conn = conn(:post, "/")
+
+    {adapter, _state} = conn.adapter
+
+    assert {:ok, params, _} = adapter.parse_req_multipart(%{req_body: multipart}, [{:boundary, "----w58EW1cEpjzydSCq"}], &Plug.Parsers.MULTIPART.handle_headers/1)
+
+    assert params["name"] == "hello"
+    assert params["status"] == ["choice1", "choice2"]
+    assert params["empty"] == nil
+
+    assert %Plug.Upload{} = file = params["pic"]
+    assert File.read!(file.path) == "hello\n\n"
+    assert file.content_type == "text/plain"
+    assert file.filename == "foo.txt"
   end
 
   test "use existing conn.host if exists" do