NewRelic.Instrumented.HTTPoison.Error.__struct__/0 is undefined, cannot expand struct NewRelic.Instrumented.HTTPoison.Error

[brunozrk]

When using the Pre-Instrumented Modules - HTTPoison and doing pattern matching in HttpPoison response, eg.:

{:error, %HTTPoison.Error{reason: reason}} = response

it raises an error at compilation time:

NewRelic.Instrumented.HTTPoison.Error.__struct__/0 is undefined, cannot expand struct NewRelic.Instrumented.HTTPoison.Error

I don't know if there is a trick to do in NewRelic.Instrumented.HTTPoison to solve this error, I solved the problem using a different alias:

alias NewRelic.Instrumented.HTTPoison, as: NRHTTPoison

and then: NRHTTPoison.post(...)

but it looks ugly 😢

Environment

• Elixir & Erlang version (elixir -v):
  Erlang/OTP 20 [erts-9.0] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:10] [hipe] [kernel-poll:false]
  Elixir 1.7.3 (compiled with Erlang/OTP 20)

• Agent version (mix deps | grep new_relic_agent):
  new_relic_agent 1.0.2 (Hex package) (mix)
  locked at 1.0.2 (new_relic_agent) 4528c139

[binaryseed]

Thanks we'll look into how to solve this

[binaryseed]

Do you have to pattern match on the exception name? HTTPoison only has one exception type. This would also work...

{:error, %{reason: reason}} = response

I'll look into mirroring the Error struct but this ^ might fix it for you too

[binaryseed]

One thing you can do is reference the top level module via Elixir. like this:

{:error, %Elixir.HTTPoison.Error{}} = HTTPoison.get("localhost:12345")

[brunozrk]

summarizing, we have 3 options:

• first

alias NewRelic.Instrumented.HTTPoison, as: NRHTTPoison

and then: NRHTTPoison.post(...)

• second

case response do
   {:error, {reason: reason}} ->
           ...
   {:ok, {status_code: status, body: body}} ->
      case status do
            200 ->
              ...
            _ ->
              ...
      end
end

• third

case response do
   {:error, %Elixir.HTTPoison.Error{reason: reason}} ->
           ...
   {:ok, %Elixir.HTTPoison.Response{status_code: status, body: body}} ->
      case status do
            200 ->
              ...
            _ ->
              ...
      end
end

I liked the third option, modifying the documentation should help, and I think mirroring the struts won't be necessary, what do you think?

[binaryseed]

I'll update the docs to point folks to the 2nd and 3rd option based on their preferences.

Thanks for reporting this!