Missing support for compilers config in Mix.install/2

[Eiji7]

Elixir and Erlang/OTP versions

Found no support at all up to main branch. Erlang version N/A.

Operating system

N/A - that's Elixir issue regardless of OS

Current behavior

See [] (empty list) value for compilers config regardless of passed options.

elixir/lib/mix/lib/mix.ex

Lines 723 to 737 in 6730d66

	config = [
	version: "0.1.0",
	build_embedded: false,
	build_per_environment: true,
	build_path: "_build",
	lockfile: "mix.lock",
	deps_path: "deps",
	deps: deps,
	app: :mix_install,
	erlc_paths: ["src"],
	elixirc_paths: ["lib"],
	compilers: [],
	consolidate_protocols: consolidate_protocols?,
	config_path: config_path
	]

Expected behavior

Some libraries requires custom mix compilers to work. The problem was found by me when I want to test tria in my scripts, but applies to other libraries as well, for example elixir_make.

Note: When creating this issue I was thinking about it more like a bug report rather than a proposal, because Mix.install/2 was added to help working with dependencies in single file scripts and missing option blocks developers from doing so in specific use cases.

[wojtekmach]

When we set :compilers on a Mix project, that option is used to compile that project, not its dependencies. Changing Mix.install is trivial:

diff --git a/lib/mix/lib/mix.ex b/lib/mix/lib/mix.ex
index dedfe9803..9f9182f86 100644
--- a/lib/mix/lib/mix.ex
+++ b/lib/mix/lib/mix.ex
@@ -754,7 +754,7 @@ def install(deps, opts) when is_list(deps) and is_list(opts) do
           app: :mix_install,
           erlc_paths: ["src"],
           elixirc_paths: ["lib"],
-          compilers: [],
+          compilers: Keyword.get(opts, :compilers, []),
           consolidate_protocols: consolidate_protocols?,
           config_path: config_path
         ]

but I'm not sure if it would anything for your use case. Give it a try!

[josevalim]

Hi @Eiji7!

The compilers: [] option applies to current project but, in case of Mix install, there is no current project, so that option does nothing regardless of value. Dependencies that have set their :compilers option will have their options respected regardless of this setting.

Also note that setting the compilers: option in your mix.exs is not going to affect your dependencies.

In other words, I am not sure the requested feature has any use and the reported scenario "Some libraries requires custom mix compilers to work" works today (you can try installing stb_image for example).