Same request fails with some adapters and succeeds with others

[gaiabeatrice]

Hello, I am migrating some of our requests from HTTPoison to Tesla and I found some requests are failing if I use httpc or Mint as the adapters, while Hackney works. I understand that it is because of HTTPoison using Hackney under the hood.

It would be nice, however to see some sort of uniformity in handling requests so that switching to a new adapter can be as seamless as possible.

uri = <URI>
method = :post
body = nil
headers: [
  {"Content-type", "application/json"},
  {"Accept", "application/json"},
  {"Authorization",
   "Bearer <TOKEN>"}
]
query = []

Tesla.request(client(),
   method: method,
   url: uri,
   body: body,
   headers: headers,
   query: query
)

defp client() do
    Tesla.client([Tesla.Middleware.JSON])
end

If I run that with Hackney it works well, if I use httpc for example I get this error

** (FunctionClauseError) no function clause matching in :httpc.request/5

    The following arguments were given to :httpc.request/5:

        # 1
        :post

        # 2
        {'<URL>',
         [
           {'Content-type', 'application/json'},
           {'Accept', 'application/json'},
           {'Authorization',
            'Bearer <TOKEN>'}
         ]}

        # 3
        [autoredirect: false]

        # 4
        []

        # 5
        :default

    (inets) httpc.erl:149: :httpc.request/5
    (tesla) lib/tesla/adapter/httpc.ex:52: Tesla.Adapter.Httpc.request/2
    (tesla) lib/tesla/adapter/httpc.ex:22: Tesla.Adapter.Httpc.call/2
    (tesla) lib/tesla/middleware/json.ex:54: Tesla.Middleware.JSON.call/3

[teamon]

Seems like an issue with adapters not handling POST request with nil body.

@gaiabeatrice Could you provide a test case in https://github.com/teamon/tesla/blob/master/test/support/adapter_case/basic.ex ?

[chulkilee]

• Httpc does not accept nil as body. See http://www1.erlang.org/doc/man/httpc.html
• Tesla uses any for body: https://hexdocs.pm/tesla/Tesla.Env.html#t:body/0
• Hackney accepts term (any) for body: https://hexdocs.pm/hackney/hackney.html#request-5

You can just pass empty string ("").

{:ok, _} =
  Tesla.client([Tesla.Middleware.JSON], Tesla.Adapter.Httpc)
  |> Tesla.post("https://httpbin.org/post", "")

We may handle the nil value at Tesla.Adapter.Httpc as it's easy to handle - but at the same time I'm not sure how much we have to make adapter behave exactly same way, since at some level it's not possible at all.

[teamon]

I think it makes sense to:

• [ ] Add a basic adapter test case to sending POST request with nil body
• [ ] Handle nil body for adapters that fail

[fbergero]

Hey @teamon I'm now to tesla but would like to help on this issue. I'll try to first create the test that fails. Any other guidance?

[fbergero]

I've just seen that @gaiabeatrice has open a PR for this so I'll find some other issue to work on

[yordis]

I couldn't test :gun, I kept getting the following error:

iex(2)> {:ok, _} = Application.ensure_all_started(:gun)
** (MatchError) no match of right hand side value: {:error, {:cowlib, {'no such file or directory', 'cowlib.app'}}}

But, all the other adapters support passing nil body as far as I can tell:

{:ok, _} = Application.ensure_all_started(:hackney)
# {:ok, _} = Application.ensure_all_started(:gun)
{:ok, _} = :ibrowse.start()
{:ok, _} = Finch.start_link(name: MyFinch)

adapters = [
  {Tesla.Adapter.Httpc, []},
  {Tesla.Adapter.Hackney, []},
  {Tesla.Adapter.Mint, []},
  {Tesla.Adapter.Ibrowse, []},
  {Tesla.Adapter.Finch, [name: MyFinch]},
  # {Tesla.Adapter.Gun, []},
]

[nil, nil, nil, nil, nil] = for adapter <- adapters do
  client = Tesla.client([Tesla.Middleware.JSON], adapter)
  {:ok, res} = Tesla.post(client, "https://httpbin.org/post", nil)
  nil = res.body["json"]
end

uri = "https://httpbin.org/post"
method = :post
body = nil
headers = [
  {"Content-type", "application/json"},
  {"Accept", "application/json"},
  {"Authorization",
    "Bearer <TOKEN>"}
]
query = []
{:ok, _} = Tesla.request(Tesla.client([Tesla.Middleware.JSON]),
  method: method,
  url: uri,
  body: body,
  headers: headers,
  query: query
)

I will close this. If you face an issue with :gun package, please open a new issue, but as far as I can tell. It is working.