Add project.plan-nix.freeze
#1055
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Issues with `cabal.project.freeze` files can be tricky to debug. While it is possible to run without a freeze file and look at the `plan-nix` or `plan-nix.json` (the `plan.json`) created when haskell.nix configured the project, it would be nice to also have the output of `cabal freeze` as it will be in the correct format and contains a different subset of `plan.json` than the `plan-nix`. This might also be useful for automating updating of `.freeze` files.
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| @@ -436,7 +437,7 @@ 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).
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Issues with `cabal.project.freeze` files can be tricky to debug. While it is possible to run without a freeze file and look at the `plan-nix` or `plan-nix.json` (the `plan.json`) created when haskell.nix configured the project, it would be nice to also have the output of `cabal freeze` as it will be in the correct format and contains a different subset of `plan.json` than the `plan-nix`. This might also be useful for automating updating of `.freeze` files.
Issues with
cabal.project.freezefiles can be tricky to debug.While it is possible to run without a freeze file and look
at the
plan-nixorplan-nix.json(theplan.json) created whenhaskell.nix configured the project, it would be nice to
also have the output of
cabal freezeas it will be in thecorrect format and contains a different subset of
plan.jsonthan the
plan-nix.This might also be useful for automating updating of
.freezefiles.