Ensure connection errors return the expected error tuple

[carrascoacd]

Bug

We encountered an in-the Mint adapter in Tesla. The error arises when we try to issue a new request but the connection was previously closed by the server. The response is a tuple of three elements, including the closed connection struct, but only two elements are expected in the behavior. In consequence, if we chain the Logger middleware this error happens: FunctionClauseError: no function clause matching in Tesla.Middleware.Logger.log_level/2

We can reproduce it by closing the connection before issuing the request, an example is:

Given this module

defmodule A do
  use Tesla

  adapter Tesla.Adapter.Mint
  
  plug Tesla.Middleware.Logger
  
  def get(), do: get("http://localhost:5984/ping")
end

iex(15)> A.get
** (FunctionClauseError) no function clause matching in Tesla.Middleware.Logger.log_level/2

    The following arguments were given to Tesla.Middleware.Logger.log_level/2:

        # 1
        {:error,
         %Mint.HTTP1{
           host: "localhost",
           port: 5984,
           request: nil,
           streaming_request: nil,
           socket: #Port<0.13>,
           transport: Mint.Core.Transport.TCP,
           mode: :active,
           scheme_as_string: "http",
           requests: {[], []},
           state: :closed,
           buffer: "",
           proxy_headers: [],
           private: %{},
           log: false
         }, %Mint.TransportError{reason: :closed}}

        # 2
        []

    Attempted function clauses (showing 2 out of 2):

        defp log_level({:error, _}, _)
        defp log_level({:ok, env}, config)

    (tesla 1.6.0) lib/tesla/middleware/logger.ex:213: Tesla.Middleware.Logger.log_level/2
    (tesla 1.6.0) lib/tesla/middleware/logger.ex:203: Tesla.Middleware.Logger.call/3

Proposed solution

• Ensure we handle properly the connection errors. As example this should be logged:

iex(16)> A.get

    09:33:28.750 [error] GET http://localhost:5984/ping -> error: %Mint.TransportError{reason: :closed} (2.600 ms)
    {:error, %Mint.TransportError{reason: :closed}}
    
    09:33:28.750 [debug]
    >>> REQUEST >>>
    (no query)
    (no headers)
    (no body)
    
    <<< RESPONSE ERROR <<<
    %Mint.TransportError{reason: :closed}

PTAL @yordis. Thanks!

[yordis]

Do you mind bumping the version here:

tesla/mix.exs

Line 5 in 04a94e6

@version "1.6.0"

[carrascoacd]

Done!