[staging-24.05] haskellPackages: backports from #315167 #318354
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Previously, we would set GHC_PACKAGE_PATH after configure, the reasons being that 1. Setup.hs configure forbids this from being set since it can make a build fail that would otherwise succeed (since it influences how GHC behaves when invoked by Cabal). 2. Setting GHC_PACKAGE_PATH being set is sound in our case, since we set it precisely to the packages available to Cabal at configure time, so there should be no room for a mismatch. 3. Some test suites require GHC_PACKAGE_PATH or GHC_ENVIRONMENT to be set, so they can invoke GHC(i) with build dependencies available. Cabal >= 3.12 forbids GHC_PACKAGE_PATH from being set after <haskell/cabal@d6e38041a7c778fadf8f416>. Setting GHC_ENVIRONMENT would be possible, but is cumbersome without cabal-install (which has the handy cabal exec command which takes care of that). Additionally, it is not clear if it'll remain possible to do that: <haskell/cabal#7792>. Our solution to Cabal 3.12's change is to be more targeted about setting GHC_PACKAGE_PATH: We _just_ set it for the actual test suite executable. This can be achieved by using --test-wrapper which when given is invoked by Cabal to run the test suite. Here we can set any environment variables after Cabal has already done its environment checks. As long as we don't do anything stupid, this should be unproblematic. Users can also arbitrarily influence what GHC_PACKAGE_PATH will contain using the NIX_GHC_PACKAGE_PATH_FOR_TEST environment variable. This is un(der)documented for now, since I want to keep some wiggle room for changing stuff in the coming weeks. Also it's rarely necessary to actually touch this variable. (cherry picked from commit 120f242)
After 120f242, GHC_PACKAGE_PATH isn't set implicitly in installPhase anymore. Instead we achieve the same by telling the Makefile the exact ghc command line to use. As a benefit, we can now cleanly separate build and host in this case: We used to (implicitly) reuse the host package db. Now we can explicitly request the package db also used for building Setup.hs. (cherry picked from commit 482ab92)
It is somewhat curious that it behaves differently exclusively here, but I don't think it is necessary to stop shipping a package due to floating point arithmetic error—it would be unreasonable to assume there were none… See ekmett/ad#113. (cherry picked from commit d902325)
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Ref #315167.
Things done
nix.conf? (See Nix manual)sandbox = relaxedsandbox = truenix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage./result/bin/)Add a 👍 reaction to pull requests you find important.