Support any enumerable in mutlipart

lib/req/steps.ex

@@ -398,7 +398,9 @@ defmodule Req.Steps do
 
         * `File.Stream`
 
-        * `{value, options}` tuple. Supported options are `:filename` and `:content_type`
+        * `Enumerable`
+
+        * `{value, options}` tuple. Supported options are: `:filename`, `:content_type`, `:content_length`
 
     * `:json` - if set, encodes the request body as JSON (using `Jason.encode_to_iodata!/1`), sets
       the `accept` header to `application/json`, and the `content-type` header to `application/json`.
@@ -419,6 +421,14 @@ defmodule Req.Steps do
       iex> resp.body["files"]
       %{"b" => "2"}
 
+  Encoding streaming form (`multipart/form-data`):
+
+      iex> stream = Stream.cycle(["abc"]) |> Stream.take(3)
+      iex> fields = [file: {stream, filename: "b.txt", content_length: 9}]
+      iex> resp = Req.post!("https://httpbin.org/anything", form_multipart: fields)
+      iex> resp.body["files"]
+      %{"file" => "abcabcabc"}
+
   Encoding JSON:
 
       iex> Req.post!("https://httpbin.org/post", json: %{a: 2}).body["json"]

lib/req/utils.ex

@@ -464,6 +464,11 @@ defmodule Req.Utils do
     }
   end
 
+  defp add_form_parts({_parts1, size1}, {_parts2, size2})
+       when not is_integer(size1) or not is_integer(size2) do
+    raise ArgumentError, "multipart part sizes must be integers"
+  end
+
   defp add_form_parts({parts1, size1}, {parts2, size2})
        when is_list(parts1) and is_list(parts2) do
     {[parts1, parts2], size1 + size2}
@@ -474,7 +479,7 @@ defmodule Req.Utils do
   end
 
   defp encode_form_part({name, {value, options}}, boundary) do
-    options = Keyword.validate!(options, [:filename, :content_type])
+    options = Keyword.validate!(options, [:filename, :content_type, :content_length])
 
     {parts, parts_size, options} =
       case value do
@@ -504,6 +509,12 @@ defmodule Req.Utils do
             end)
 
           {stream, size, options}
+
+        enum ->
+          Enumerable.impl_for!(enum)
+          size = Keyword.get(options, :content_length, 0)
+
+          {enum, size, options}
       end
 
     params =
@@ -514,11 +525,11 @@ defmodule Req.Utils do
       end
 
     headers =
-      if content_type = options[:content_type] do
-        ["content-type: ", content_type, @crlf]
-      else
-        []
-      end
+      [
+        maybe_content_type(options),
+        maybe_content_length(options)
+      ]
+      |> Enum.reject(&is_nil/1)
 
     headers = ["content-disposition: form-data; name=\"#{name}\"", params, @crlf, headers]
     header = [[@crlf, "--", boundary, @crlf, headers, @crlf]]
@@ -529,6 +540,18 @@ defmodule Req.Utils do
     encode_form_part({name, {value, []}}, boundary)
   end
 
+  defp maybe_content_type(options) do
+    if content_type = options[:content_type] do
+      ["content-type: ", content_type, @crlf]
+    end
+  end
+
+  defp maybe_content_length(options) do
+    if content_length = options[:content_length] do
+      ["content-length: ", Integer.to_string(content_length), @crlf]
+    end
+  end
+
   @doc """
   Loads .netrc file.
 

test/req/utils_test.exs

@@ -175,6 +175,45 @@ defmodule Req.UtilsTest do
              """
     end
 
+    test "raise when size is not integer" do
+      assert_raise ArgumentError, fn ->
+        enum = Stream.cycle([1]) |> Stream.take(1)
+        Req.Utils.encode_form_multipart([field1: {enum, content_length: "10"}], boundary: "foo")
+      end
+    end
+
+    test "content-length" do
+      %{content_type: content_type, body: body, size: size} =
+        Req.Utils.encode_form_multipart([field1: {"a", content_length: 11}], boundary: "foo")
+
+      body = IO.iodata_to_binary(body)
+
+      assert size == byte_size(body)
+      assert content_type == "multipart/form-data; boundary=foo"
+
+      assert body == """
+             \r\n\
+             --foo\r\n\
+             content-disposition: form-data; name=\"field1\"\r\n\
+             content-length: 11\r\n\
+             \r\n\
+             a\r\n\
+             --foo--\r\n\
+             """
+    end
+
+    test "can accept any enumerable" do
+      enum = Stream.cycle(["a"]) |> Stream.take(1)
+
+      %{body: body, size: size} =
+        Req.Utils.encode_form_multipart([field1: {enum, content_length: 11}], boundary: "foo")
+
+      body = body |> Enum.to_list() |> IO.iodata_to_binary()
+
+      # content_length is +10 of actual size
+      assert size == byte_size(body) + 10
+    end
+
     @tag :tmp_dir
     test "can return stream", %{tmp_dir: tmp_dir} do
       File.write!("#{tmp_dir}/2.txt", "22")