🎅 Fetch before rebuild

[flip111]

Fix #1110

[f-f]

I don't think this is fixing the issue - the dependencies from the build plan are not passed in anywhere, and these are the ones we need to fetch.

A good first step for a fix would be to write a test that replicates the issue in #1110. After we get CI to fail because of that we can then write the correct patch.

[flip111]

I'm not a fan of ttd i rather write the patch first if i go ahead with this. Should Fetch.run called multiple times for each dependency or can i pass all the deps at once?

[f-f]

This is not about TTD, but rather about replicating the failure in a standard environment (CI). If we can't replicate we can't fix.

[flip111]

Can the registry be queried as to what is the latest version of a package?

[f-f]

Why would we need that? We'll need to build with whatever versions the solver returns, which is not always going to be the latest one.

[flip111]

As new versions get added to the registry, the solver might resolve to something else. I expect the test to start breaking.

[f-f]

I expect the test to start breaking.

It's entirely possible to have a test that doesn't break over time - we'll need to set the version bounds to be different than what the package set contains.

[flip111]

In #1110 i don't think it was relevant that an outdated package 0.4.1 was available in the cache. The problem should just reproduce when removing any package from the cache which then should be refetched before rebuild. That the problem occurs due to an upgraded version of a dependency is not relevant to test the solution.

[flip111]

The test passes but i don't think it works correctly. Not sure what is happening

[f-f]

This has been discussed on Discord, but I'll report here as well:
Spago uses a global cache and I think that's ultimately the reason why the new test is not working - you are deleting the package from the local cache, but Spago will find it in the global cache so it just copies it back there.
The user-facing command to get the location of the global cache is spago ls paths, but in tests you can use the Spago.Paths module

[flip111]

Superseed by #1283