Support YAML files outside package directories about haskell.nix HOT 7 CLOSED

@AshleyYakeley thank you for this suggestion. I doubt we'd want to relax the cleaning much. We treat packages as singular units as that is how packages from hackage, as well as sdist packaging works. Thus we detect the case of ill specified packages early and not late in the process when releases have to be cut.

Even if we allowed somehow to retain a file outside of the tree, where would that point to after unpacking the package into an isolated location? I'm not sure if hardlinks might help in your situation.

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A package from Hackage is indeed a singular unit, but it includes a cabal file. The source directory does not include a cabal file before hpack is run (e.g. via stack).

Another (better?) solution would be to do cleaning only after hpack has generated the cabal file.

Even if we allowed somehow to retain a file outside of the tree, where would that point to after unpacking the package into an isolated location?

It turns out that cleaning a subdirectory retains the subdirectory structure within the isolated location, so there's actually a place for files elsewhere in the tree.

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We already don't clean components if they are using hpack, presumably to support this sort of thing: https://github.com/input-output-hk/haskell.nix/blob/master/builder/comp-builder.nix#L106

So something is going wrong there.

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I'm examining this with a local copy of haskell.nix. Adding in __trace functions, I can see the canCleanSource flag is correctly false at that point. However, cleanSourceWith gets called in various other places which will omit the file.

from haskell.nix.

@michaelpj, #1925 shows a small hack to work around this issue, just to get an idea of where the problematic cleaning is done.

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(my flake.nix)

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This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

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