fix(#5008): "Invalid option --internal-re-exec-version" error when using "nix" with options "enable: true", "pure: true", "shell-file: .." -> prevent entering "nix-shell --pure" recursively by exporting STACK_IN_NIX_SHELL properly

[srghma]

fixes ##5008

I've run this on srghma/generate-all-tests@50630d2

here is the output

$ ~/projects/stack/.stack-work/dist/x86_64-linux-nix/Cabal-2.0.1.0/build/stack/stack build --verbose
Version 2.2.0, Git revision 602253507622b55ca627bf22a66e5874182e7345 (dirty) (7902 commits) PRE-RELEASE x86_64 hpack-0.31.2
2019-12-26 11:29:33.749556: [debug] Checking for project config at: /home/srghma/projects/generate-all-tests/stack.yaml
2019-12-26 11:29:33.749814: [debug] Loading project config file stack.yaml
2019-12-26 11:29:33.757926: [debug] SELECT COUNT(*) FROM "last_performed" WHERE ("action"=?) AND ("timestamp">=?); [PersistInt64 1,PersistUTCTime 2019-12-25 09:29:33.757888904 UTC]
2019-12-26 11:29:33.758500: [debug] Using package location completions from a lock file
2019-12-26 11:29:33.766725: [debug] Loaded snapshot from Pantry database.
2019-12-26 11:29:33.877276: [debug] Running hpack on /home/srghma/projects/generate-all-tests/package.yaml
2019-12-26 11:29:33.880535: [debug] hpack output unchanged in /home/srghma/projects/generate-all-tests/generate-all-tests.cabal
2019-12-26 11:29:33.896857: [debug] Migration executed: CREATE TABLE "config_cache"("id" INTEGER PRIMARY KEY,"directory" VARCHAR NOT NULL DEFAULT (hex(randomblob(16))),"type" VARCHAR NOT NULL,"pkg_src" VARCHAR NOT NULL,"active" BOOLEAN NOT NULL,"path_env_var" VARCHAR NOT NULL,"haddock" BOOLEAN NOT NULL DEFAULT 0,CONSTRAINT "unique_config_cache" UNIQUE ("directory","type"))
2019-12-26 11:29:33.897105: [debug] Migration executed: CREATE TABLE "config_cache_dir_option"("id" INTEGER PRIMARY KEY,"config_cache_id" INTEGER NOT NULL REFERENCES "config_cache","index" INTEGER NOT NULL,"option" VARCHAR NOT NULL,CONSTRAINT "unique_config_cache_dir_option" UNIQUE ("config_cache_id","index"))
2019-12-26 11:29:33.897234: [debug] Migration executed: CREATE TABLE "config_cache_no_dir_option"("id" INTEGER PRIMARY KEY,"config_cache_id" INTEGER NOT NULL REFERENCES "config_cache","index" INTEGER NOT NULL,"option" VARCHAR NOT NULL,CONSTRAINT "unique_config_cache_no_dir_option" UNIQUE ("config_cache_id","index"))
2019-12-26 11:29:33.897339: [debug] Migration executed: CREATE TABLE "config_cache_dep"("id" INTEGER PRIMARY KEY,"config_cache_id" INTEGER NOT NULL REFERENCES "config_cache","ghc_pkg_id" VARCHAR NOT NULL,CONSTRAINT "unique_config_cache_dep" UNIQUE ("config_cache_id","ghc_pkg_id"))
2019-12-26 11:29:33.897435: [debug] Migration executed: CREATE TABLE "config_cache_component"("id" INTEGER PRIMARY KEY,"config_cache_id" INTEGER NOT NULL REFERENCES "config_cache","component" BLOB NOT NULL,CONSTRAINT "unique_config_cache_component" UNIQUE ("config_cache_id","component"))
2019-12-26 11:29:33.897980: [debug] PATH is: Just "/home/srghma/.gem/ruby/2.4.0/bin:/home/srghma/.node_modules/bin:/home/srghma/bin:/run/wrappers/bin:/home/srghma/.nix-profile/bin:/etc/profiles/per-user/srghma/bin:/nix/var/nix/profiles/default/bin:/run/current-system/sw/bin:./node_modules/.bin"
2019-12-26 11:29:33.898159: [debug] Using a nix-shell environment from file: /home/srghma/projects/generate-all-tests/stack-shell.nix
2019-12-26 11:29:33.898535: [debug] Run process: /run/current-system/sw/bin/nix-shell /home/srghma/projects/generate-all-tests/stack-shell.nix --arg ghc "with (import <nixpkgs> {}); haskell.compiler.ghc865" --run "export STACK_IN_NIX_SHELL=1;  '/home/srghma/projects/stack/.stack-work/dist/x86_64-linux-nix/Cabal-2.0.1.0/build/stack/stack' $STACK_IN_NIX_EXTRA_ARGS '--internal-re-exec-version=2.2.0' 'build' '--verbose'"

[qrilka]

@srghma this variable should be set in

stack/src/Stack/Nix.hs

Line 79 in 06cda68

,T.pack inNixShellEnvVar <> "=1; "

, if you have a shell file then I suppose you should set this variable in that file.
Though the intended semantics wasn't documented anywhere so it's not quite clear.

[srghma]

this variable should be set in

updated, tnx

if you have a shell file then I suppose you should set this variable in that file

yes, I have mentioned that this is one of possible ways to overcome this issue #5008 (comment)

[qrilka]

@srghma I think it would be good to remove setting inNixShellEnvVar twice in case when shell file is not used. After that we could merge this.
If you have time it would help if you could add a simple integration test with a shell.nix

[srghma]

twice in case when shell file is not used

what do you mean?

[qrilka]

See line

stack/src/Stack/Nix.hs

Line 79 in e12c4f0

,T.pack inNixShellEnvVar <> "=1; "

- it sets the same variable but using nix, not shell

[srghma]

ah, you want me to change

                           ,["--run", unwords ("export " <> inNixShellEnvVar <> "=1; ":cmnd:"$STACK_IN_NIX_EXTRA_ARGS":args')]

to something like

let exportInNixShellEnvVarIfShellFileIsUsed = if isJust mshellFile then "export " <> inNixShellEnvVar <> "=1; " else ""
....
                           ,["--run", exportInNixShellEnvVarIfShellFileIsUsed. unwords (cmnd:"$STACK_IN_NIX_EXTRA_ARGS":args')]

[qrilka]

@srghma just dropping that line 79 would be enough if we need to set this var anyway

[srghma]

added

[qrilka]

Thanks, let's now wait for CI to pass.

[qrilka]

Thanks for your efforts @srghma but I think now I understand Nix integration a bit better and it looks like I was wrong in my previous ideas and this PR isn't actually need. As it's said in the docs you need to use buildStackProject from nixpkgs as it adds details needed for a proper integration between Stack and Nix. As for the STACK_IN_NIX_SHELL variable, it gets set in https://github.com/NixOS/nixpkgs/blob/713a45ecf79a4b4c632819f1c898d3e66c77bdd2/pkgs/development/haskell-modules/generic-stack-builder.nix#L28

[srghma]

ok, agree, thanks to you too