From: "jeremyevans0 (Jeremy Evans) via ruby-core" <ruby-core@...>
Date: 2024-01-07T00:10:58+00:00
Subject: [ruby-core:116058] [Ruby master Feature#20152] mkmf / extconf: Add a proper way to not compile the extension

Issue #20152 has been updated by jeremyevans0 (Jeremy Evans).


nobu (Nobuyoshi Nakada) wrote in #note-5:
> byroot (Jean Boussier) wrote in #note-2:
> > This would be called in `extconf.rb`
> 
> Does `skip_compilation` just make a Makefile does nothing?
> Then it won't be able to fix the issue that `make` is needed, since `make` is called outside `extconf.rb`.

I agree that this isn't a `mkmf`/`extconf.rb` issue.  This is a rubygems issue.  I think the easiest way to fix this would be for rubygems to check for a `skip-compilation-RUBY_ENGINE` file in the same directory as `extconf.rb`.  If it exists, do not run `extconf.rb` or `make`.  If it exists after calling `extconf.rb`, do not call `make`.  This fixes cases where an extension is not needed for a certain engine, as well as cases where an extension is not needed in certain configurations, such as when a pure-ruby implementation is also shipped in the same gem, and a native library necessary for the native extension is not available.

----------------------------------------
Feature #20152: mkmf / extconf: Add a proper way to not compile the extension
https://bugs.ruby-lang.org/issues/20152#change-106056

* Author: byroot (Jean Boussier)
* Status: Open
* Priority: Normal
----------------------------------------
### Context

There are various gems that ship with a native extension as a way to speedup part of the gem, but also ship with a pure Ruby version of these methods as a fallback. So they only want to compile the extension if the platform supports it, and if not, just fallback to the slightly slower Ruby version.

Right now users rely on one of two hacks to do this. Either they create an empty Makefile, but then still depend on `make` being available, or publish platform specific packages without any extension in them.

Examples:

  - [`bootsnap` skip compilation if not on MRI or TruffleRuby](https://github.com/Shopify/bootsnap/blob/070151f1305f23102365d6b4476a91c02dead35a/ext/bootsnap/extconf.rb)
  - [`erb` has an extension for MRI but then need to publish a `java` version of the gem that doesn't actually contain Java code, just to skip compilation on JRuby](https://github.com/ruby/erb/issues/52)
  - [`hiredis-client` skips the compilation for Windows and non-MRI rubies](https://github.com/redis-rb/redis-client/blob/1ab081c1d0e47df5d55e011c9390c70b2eef6731/hiredis-client/ext/redis_client/hiredis/extconf.rb#L10-L17)

### Feature

It would be very useful to have some proper first class API to skip compiling the extension. 

Something like:

```ruby
require "mkmf"

if RUBY_ENGINE != "ruby" || RUBY_PLATFORM.match?(/mswin/)
  skip_compilation
else
  # ...
end
```

cc @k0kubun @headius 




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