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Merged
merged 4 commits into from
Mar 4, 2021
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Add project.plan-nix.freeze #1055

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41fd5e6
Add `project.plan-nix.freeze`
hamishmack Feb 23, 2021
2517109
Merge remote-tracking branch 'origin/master' into hkm/plan-nix.freeze
hamishmack Mar 4, 2021
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hamishmack Mar 4, 2021
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hamishmack Mar 4, 2021
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17 changes: 15 additions & 2 deletions lib/call-cabal-project-to-nix.nix
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Original file line number Diff line number Diff line change
Expand Up @@ -385,7 +385,11 @@ let
LANG = "en_US.UTF-8";
meta.platforms = pkgs.lib.platforms.all;
preferLocalBuild = false;
outputs = ["out" "json"];
outputs = [
"out" # The results of plan-to-nix
"json" # The `plan.json` file generated by cabal and used for `plan-to-nix` input
"freeze" # The `cabal.project.freeze` file created by `cabal v2-freeze`
];
} ''
tmp=$(mktemp -d)
cd $tmp
Expand Down Expand Up @@ -421,10 +425,15 @@ let
${pkgs.lib.optionalString (cabalProjectFreeze != null) ''
cp ${pkgs.evalPackages.writeText "cabal.project.freeze" cabalProjectFreeze} \
cabal.project.freeze
chmod +w cabal.project.freeze
''}
export SSL_CERT_FILE=${cacert}/etc/ssl/certs/ca-bundle.crt
export GIT_SSL_CAINFO=${cacert}/etc/ssl/certs/ca-bundle.crt

# Using `cabal v2-freeze` will configure the project (since
# it is not configured yet), taking the existing `cabal.project.freeze`
# file into account. Then it "writes out a freeze file which
# records all of the versions and flags that are picked" (from cabal docs).
echo "Using index-state ${index-state-found}"
HOME=${
# This creates `.cabal` directory that is as it would have
Expand All @@ -436,7 +445,7 @@ let
index-state = cached-index-state;
sha256 = index-sha256-found;
}
} cabal v2-configure \
} cabal v2-freeze \
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What does this do if the user supplied a freeze file? Does it overwrite it? That would be bad, right?

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What does this do if the user supplied a freeze file? Does it overwrite it? That would be bad, right?

At this point it is running in a temp dir. It seems to do a v2-configure then save out the new version over the top.

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That seems wrong? If the user gives us a freeze file (and this function takes one) then surely we should use that unequivocally?

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It is used by cabal. The existing freeze file may not include constraints for all the packages. The one cabal outputs will be more complete. For instance if I just include constraints: any.base ==4.14.1.0 in freeze file:

% cat $(nix-build -E '(((import ./. {}).pkgs-unstable.haskell-nix.tool "ghc8104" "hello" {version = "1.0.0.2"; cabalProjectFreeze = "constraints: any.base ==4.14.1.0";}).project).plan-nix.freeze')
trace: No index state specified for hello, using the latest index state that we know about (2021-02-23T00:00:00Z)!
building '/nix/store/cb2ri159gm7i7jsblgjwa5vi69iqqk3r-cabal.project.freeze.drv'...
building '/nix/store/8y5mcs03rr7apj89na4hnn28d0p0pakn-hello-plan-to-nix-pkgs.drv'...
Using index-state 2021-02-23T00:00:00Z
Warning: The package list for 'hackage.haskell.org-at-2021-02-23T000000Z' is
18681 days old.
Run 'cabal update' to get the latest list of available packages.
Warning: Requested index-state2021-02-23T00:00:00Z is newer than
'hackage.haskell.org-at-2021-02-23T000000Z'! Falling back to older state
(2021-02-22T23:55:38Z).
Resolving dependencies...
Wrote freeze file:
/private/tmp/nix-build-hello-plan-to-nix-pkgs.drv-0/tmp.R874CaSGyv/cabal.project.freeze
constraints: any.base ==4.14.1.0,
             any.ghc-prim ==0.6.1,
             hello -threaded,
             any.integer-gmp ==1.0.3.0,
             any.rts ==1.0

I get the same output for constraints: any.base ==4.*, but for constraints: any.base ==5.* cabal v2-freeze fails to find a solution. I don't know if there is a way to tell cabal to be more strict and require all the constraints to be in the cabal.project.freeze file. I guess if there is not we could build one by comparing the original version with the one it spits out and returning an error if they differ.

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Okay, if it includes the constraints from the input freeze file and gives you one with strictly more constraints then I'm fine with it. Worth a comment, though!

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I am not sure it will be "strictly more constraints". I suspect that if the input freeze file includes a constraint on a package that is not picked at all (Win32 for instance when building for linux), the output may not include a constraint at all.

I don't think that is something we should fix in Haskell.Nix though (it seems more like a cabal v2-freeze problem). I have added a comment describing .freeze as The 'cabal.project.freeze' file created by 'cabal v2-freeze'.

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I also added:

    # Using `cabal v2-freeze` will configure the project (since
    # it is not configured yet), taking the existing `cabal.project.freeze`
    # file into account.  Then it "writes out a freeze file which
    # records all of the versions and flags that are picked" (from cabal docs).

--index-state=${
# Setting the desired `index-state` here in case it was not
# from the cabal.project file. This will further restrict the
Expand All @@ -453,6 +462,10 @@ let
"--ghcjs --with-ghcjs=js-unknown-ghcjs-ghc --with-ghcjs-pkg=js-unknown-ghcjs-ghc-pkg"} \
${configureArgs}

cp cabal.project.freeze $freeze
# Not needed any more (we don't want it to wind up in the $out hash)
rm cabal.project.freeze

mkdir -p $out

# ensure we have all our .cabal files (also those generated from package.yaml) files.
Expand Down