callCabal2nix: Don't rebuild unchanged cabal file #23880
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It can be quite annoying that callCabal2nix will build a new derivation if anything in the source has changed, even if the cabal file hasn't.
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@ElvishJerricco, thanks for your PR! By analyzing the history of the files in this pull request, we identified @peti, @oxij and @3noch to be potential reviewers. |
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Very interesting approach! I'm glad it works! |
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I ignorantly wonder if this will have issues when a build requires that you copy a closure to a remote machine. I doubt it, but it's an edge case to consider. |
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See #24245 |
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…ild-cabalfile callCabal2nix: Don't rebuild unchanged cabal file (Fixed #23880)
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It can be quite annoying that callCabal2nix will build a new derivation if anything in the source has changed, even if the cabal file hasn't. In particular, you can trick Stack and Intero to work with a Nix based setup by using Stack's Nix integration and throwing away the
ghcit gives you, but Intero freaks out when it seesbuilding path(s) ...unexpectedly.This patch uses
cabal2nixon a filtered source that only includes the cabal file, then restores thesrcin the resulting derivation. This way thecabal2nix-<name>derivations will be cached between builds where non-cabal-files were changed.