Warning 'protocol has already been consolidated' when recompiling

[beno]

When I add a protocol implementation such as the following, I run into a waring when recompiling:

defimpl Poison.Encoder, for: BSON.ObjectId do
  def encode(id, options) do
    BSON.ObjectId.encode!(id) |> Poison.Encoder.encode(options)
  end
end

produces on recompile

warning: the Poison.Encoder protocol has already been consolidated, an implementation for BSON.ObjectId has no effect

Using Elixir 1.3.2, for more info see elixir-mongo/mongodb#46 (comment)

[ericmj]

This happens when calling recompile/0 in iex.

[liveresume]

I believe this is happening to you on auto-recompile as it is for me.

If you make changes to the Encoder you have to stop the app and restart to see the changes.

[chaoqu]

has this regressed? I am using Elixir 1.9.0-rc.0 (aad7aa4) (compiled with Erlang/OTP 20)

[supernintendo]

This seems to have regressed. I am using Elixir 1.8.1 with Erlang/OTP 20 and get the warning any time changed files are auto-recompiled in development.

[noelia-lencina]

I'm seeing the same warning with 1.8.2 compiled for Erlang/OTP 21. I can reproduce it every time by running r/1 in the iex console with the name of the module that's implementing the protocol (in this case the protocol is Phoenix.HTML.Safe).

[augnustin]

Same here, happens at recompilation with

elixir --version
Erlang/OTP 21 [erts-10.3.5.6] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [hipe]
Elixir 1.8.2 (compiled with Erlang/OTP 21)

Would be cleaner without it. 😄

[KalvinHom]

Hitting this all the time as well, cannot auto-recompile at all, have to manually restart the server if we use --warnings-as-errors, have to restart server for any change.

Erlang/OTP 22 [erts-10.4.3] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [hipe]
Elixir 1.9.0 (compiled with Erlang/OTP 20)

[nathanaelsousa]

Including: consolidate_protocols: Mix.env() != :dev in mix.exs seems to have solved it for me.
Like suggested here: https://hexdocs.pm/elixir/Protocol.html#module-consolidation

[bcardarella]

I'm hitting this today, I cannot resolve the warning even after adding the above mentioned changed to mix.exs

[josevalim]

@bcardarella can you try deleting _build and let me know if it works after that? I think I know why the change may not be propagating after the project is compiled.

[bcardarella]

@josevalim still happening, fwiw this is in VSCode. I'm not sure if there are build artifacts that I would need to clear out otherwise.

[josevalim]

@bcardarella they use a separate folder, _elixir_ls or .elixir_ls or similar.

[bcardarella]

Yeah I deleted those too, no success unfortunately. After I get this lib pushed to GH I can note the LOC here to see if I'm doing anything wrong

[josevalim]

If you can't reproduce it in regular code, only inside the Visual Studio Code, then it is probably best to report the issue there first. :)

[dennym]

Just hijacking this issue quickly. Currently running in this issue with Poison and the usage of defimpl.

 the Poison.Decoder protocol has already been consolidated, an implementation for Foo.Bar has no effect. If you want to implement protocols after compilation or during tests, check the "Consolidation" section in the Protocol module documentation
    │
  5 │ defimpl Poison.Decoder, for: Foo.Bar do
    │ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    │
    └─ lib/foo/bar.ex:5: (file)

This happens when using recompile/0 in iex -S mix. Usually after this I also have to hit a mix clean. Killing and restarting the iex does not lead to this issue.

Erlang/OTP 26
Elixir 1.16.0

This has no additonal tooling which could interfere and its on lain old zsh/bash.

[juped]

this occurs if you touch anything in a module with a defimpl / derived impl and recompile without a full clean build, although if you touched the impl it still gets used

minimal reproduction:

• mix new
• put the following in lib/s.ex

defmodule S do
  @derive {Inspect, only: []}
  defstruct [:field]
end

• iex -S mix
• change the module in any way, i added def a do end to it
• recompile/0 from iex

if you instead kill iex and start a new one, it recompiles without generating warnings. however, if you ever use recompile/0, the warnings will stick around permanently until you do a clean build.

[juped]

(the impl works fine even if it's edited, by the way.)

[josevalim]

Thank you, I have fixed it in main and I will backport to v1.17 too.