Mirroring (HEX_CDN and HEX_MIRROR) not working in rebar3 specific case

[matreyes]

Precheck

Checked!

Environment

elixir:1.10 (official docker version)

Current behavior

Using hex mirrors:
export HEX_MIRROR=private url
export HEX_CDN=private url

and Having repo.hex.pm blocked by firewall (you could test it pointing to localhost in /etc/hosts)

and Having Snappyer as a dependency for my project (https://hex.pm/packages/snappyer).

When I Fetch the dependencies (mix deps.get), It downloads them through the mirror without problem.
But when I try to compile the dependency, it tries to connect to repo.hex.pm to get the pc sub-dependency (https://hex.pm/packages/pc), and it fails as it is blocked.

# DEBUG=1 mix deps.compile snappyer
===> Hex get_package request failed: {error,
                                      {failed_connect,
                                       [{to_address,{"repo.hex.pm",443}},
                                        {inet,[inet],nxdomain}]}}
....

Running rebar3 compile directly from the snappyer project having exported the HEX_CDN env variable, works OK.
Running rebar3 compile directly from the snappyer project removing the HEX_CDN env variable, fails as expected.

Expected behavior

Compiling from mix (from the elixir project) should use the HEX_MIRROR (and/or HEX_CDN) env variable to fetch the pc package, but it does not.

Thanks!!!!!!!

[ericmj]

We should pass down HEX_CDN to rebar3 when we compile deps here: https://github.com/elixir-lang/elixir/blob/main/lib/mix/lib/mix/tasks/deps.compile.ex#L220.

[josevalim]

@ericmj i don't think that's the case, unfortunately. All env vars are automatically passed downstream. You can try it out with Mix.shell().cmd("env").

[matreyes]

Hi @josevalim and @ericmj

I have more info about the error.
Mix tries to use rebar3 from /root/.mix/rebar3, and in that case, it doesn't take environment variables, even if I pass them directly in the command (and I don't have any idea why this happens)
If I set MIX_REBAR3=rebar3 (so it uses /usr/local/bin/rebar3) it takes env variables and compiles successfully.

I don't know if you want to investigate more or create a kind of fallback for this issue, if not, feel free to close the thread.

And as always, thanks both of you for your amazing work ❤️.

[josevalim]

@matreyes could it be that you have an outdated rebar in /root/.mix/rebar3? Can you try /root/.mix/rebar3 --version? And what is rebar3 --version? Does it work after mix local.rebar?

[matreyes]

/root/.mix/rebar3 --version
3.13.3

rebar3 --version
3.17.0

mix local.rebar doesn't updates /root/.mix version (the other is already up to date)

[josevalim]

Ok, it seems to be rebar3 related then: erlang/rebar3#2204

If you pick a more recent Elixir version, it should install a more recent rebar3 too.

Thanks for the report!