nixos/paperless: use toShellVars for paperless-manage

[Atemu]

The homebrewed snippet didn't escape vars properly which is an issue because PAPERLESS_OCR_USER_ARGS requires a JSON string. This also meant a discrepancy between the services' env vars and paperless-manage's.

Just use the correctly functioning library function for this instead.

Description of changes

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 23.11 Release Notes (or backporting 23.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

[leona-ya]

In #242084 is some discussion about the same issue. We have to decide which approach we want to use.
I like the approach here more, but I think we should include the added docs from the PR (not strong opinion)

[erikarvstedt]

should include the added docs from

The env of the manage script must equal the env of the services. This is the default, expected case and thus needs no extra comment.

[Atemu]

The doc from the other PR is only necessary because it still doesn't quote shell vars correctly. toShellVars does.

The hint about using toJSON would be a handy addition though.

[erikarvstedt]

The hint about using toJSON would be a handy addition though.

Ah, that's what @leona-ya meant. Yes, this should be included. Here's the version from my fixup.

[leona-ya]

Oh yes, that's what I meant. I'm sorry that was imprecise

[Atemu]

Any further objections?

[erikarvstedt]

@Atemu, tbh, I'd prefer to avoid toShellVars's pessimized loop over env, given Nix' performance issues.
Alternative:

manage = pkgs.writeShellScript "manage" ''
   ${lib.concatStringsSep "\n" (mapAttrsToList (name: val: "export ${name}=${escapeShellArg val}") env)}
   exec ${pkg}/bin/paperless-ngx "$@"
'';

This avoids:

• The isValidPosixName regex check. All var names that paperless accepts are POSIX compatible.
• The value type checks. These are always strings. (We should change extraConfig.type to attrsOf str).

Weak preference, so I'm fine with ACKing this PR as it is.

[erikarvstedt]

We need the verdict of a senior Nixer. @mweinelt, can you help us out?

[erikarvstedt]

Let's get this merged.

[mweinelt]

We need the verdict of a senior Nixer. @mweinelt, can you help us out?

Slight preference for easier to read code in this case.

[github-actions]

Successfully created backport PR for release-23.05:

• [Backport release-23.05] nixos/paperless: use toShellVars for paperless-manage #245362

[Atemu]

Thanks!