Deprecate artichoke-load-path and replace it with mezzaluna-feature-loader

[lopopolo]

artichoke-load-path and mezzaluna-feature-loader both provide support for resolving Ruby sources from disk, memory, and using the RUBYLIB environment variable.

mezzaluna-feature-loader is meant to be a generalization of all of these loaders as well as an implementation of artichoke_backend::fs.

Work to be done:

• Add implementation of in-memory-only loader to mezzaluna-feature-loader.
• Add "hybrid" loader that combines in-memory, disk, and RUBYLIB loaders.
• Replace artichoke_backend::fs with mezzaluna-feature-loader.
• Simplify feature flags in artichoke and artichoke-backend to remove the ability to disable the RUBYLIB loader. Loader is either "full" or in-memory.
• Remove artichoke-load-path code, Cargo.toml entry, and CI steps.

[lopopolo]

It looks like these (old) issues might be feasible once this work lands because mezzaluna-feature-loader tracks the set of loaded features:

• Implement $LOAD_PATH #11
• Set $" in Kernel#require #170

[lopopolo]

mezzaluna-feature-loader stores load paths as PathBuf but SHOULD guarantee that these load paths can be converted to bytes so they can be turned into an Array of Strings. On wasi and unix targets, Path and OsStr are freely convertible to bytes. On all other platforms, ensure load paths are valid UTF-8 with OsStr::to_str.

[lopopolo]

I need to add a separate extension hook loader in mezzaluna_feature_loader::loaders.

[lopopolo]

The existing disk loader in artichoke_backend::load_path::Native does not restrict CWD-relative requires to "explicit relative paths.

MRI

$ echo 'puts "here in the rubylib"' > a.rb
$ ruby -e 'require "a"'
<internal:/usr/local/var/rbenv/versions/3.2.2/lib/ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:85:in `require': cannot load such file -- a (LoadError)
        from <internal:/usr/local/var/rbenv/versions/3.2.2/lib/ruby/3.2.0/rubygems/core_ext/kernel_require.rb>:85:in `require'
        from -e:1:in `<main>'
$ ruby -e 'require "./a"'
here in the rubylib
$ RUBYLIB=. ruby -e 'require "a"'
here in the rubylib

Artichoke

$ echo 'puts "here in the rubylib"' > a.rb
$ cargo run -q --bin artichoke -- -e 'require "a"'
here in the rubylib
$ cargo run -q --bin artichoke -- -e 'require "./a"'
here in the rubylib
$ RUBYLIB= cargo run -q --bin artichoke -- -e 'require "a"'
here in the rubylib

Root Cause

The Native loader directly feeds paths to File::open to check validity without first checking if they are explicit relative (and therefore meant to be resolved reltive to CWD rather than the load path).

artichoke/artichoke-backend/src/load_path/native.rs

Lines 29 to 35 in 53b84b7

	pub fn resolve_file(&self, path: &Path) -> Option<PathBuf> {
	if File::open(path).is_ok() {
	Some(path.to_owned())
	} else {
	None
	}
	}