YAML::Store dependency for pstore is required and fails on Ruby 4.0

[ekohl]

YAML::Store has this require statement:

yaml/lib/yaml/store.rb

Lines 7 to 10 in 79b6b15

	begin
	require 'pstore'
	rescue LoadError
	end

But really it directly inherits from PStore:

yaml/lib/yaml/store.rb

Line 43 in 79b6b15

class YAML::Store < PStore

Since Ruby 4.0 pstore is a bundled gem instead of a default gem: https://www.ruby-lang.org/en/news/2025/12/25/ruby-4-0-0-released/#stdlib-updates

The following bundled gems are promoted from default gems.
pstore 0.2.0
0.1.4 to v0.2.0

Though I think https://stdgems.org/pstore/ provides a clearer overview.

I'm not sure what is best: make yaml depend on pstore in the gemspec or simply make it a soft dependency. In either case, the LoadError shouldn't be silently supressed.

[boof]

IMHO, this is a hard dependency and should be added to the gemspec. IDK the minimum version, though.

[boof]

After thinking about it a little bit I also thought about extracting the store functionality would be the way to go.

After giving it more thought, I think it is fine to leave it as it is for the major part.

With Ruby 4 the warning disappears and an exception will be raised when the file is being loaded.
The only thing I'd change is to emit instructions when catching the LoadError but still let it fail with the exception.

Another option would be to include this into PStore instead of YAML. There, they can simply load Psych.