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pubgrub-rs / advanced_dependency_providers

experiment with the DependencyProvider trait
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"replacements" #2

Open Eh2406 opened 4 years ago

Eh2406 commented 4 years ago

"replacements" (in cargo the patch section and the replace) are a way to substitute the code for one package with some other code. In dart it is called dependency-overrides

This issue is to split off and continue the conversation from https://github.com/pubgrub-rs/pubgrub/issues/39.

Eh2406 commented 4 years ago

To summarize the comments from https://github.com/pubgrub-rs/pubgrub/issues/39 so far:

mpizenberg: https://github.com/pubgrub-rs/pubgrub/issues/39#issuecomment-710786729

Patch

It seems that a patch replaces directly the list of existing versions of a package by one explicitely provided in the patch. I tend to believe this is then just a matter of doing exactly that a DependencyProvider implementation.

Replace

Are the versions specified authorized to be new (non-existing in crates)? If not, this is just a matter of adjusting the get_dependencies method of a DependencyProvider implementation. If yes, it also needs to adjust the list_available_versions.

Eh2406 commented 4 years ago

I think the bugs in Cargo's resolver have to do with the fact that a selected version can report its package name, but with "replacements" that may not be the same as the name the dependency asked for. In pubgrub, thanks to @mpizenberg's foresight to use generics, we know that we never rely on V.get_package() == P for anything, as we did not ask for a get_package method. As such I think you are wright, it is just technical complexity in the implementation of a DependencyProvider