python3Packages.pyproj: change data dir priorities

[kidanger]

Description of changes

Because the ${pkgs.proj}/share/proj folder always exist, the user cannot override the data dir with the environment variable PROJ_DATA as usually possible with proj and pyproj. This PR changes the priority, to first check the environment variable before falling back to proj's folder.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• 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/)
• 24.05 Release Notes (or backporting 23.05 and 23.11 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.

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[imincik]

What about setting multiple paths like this PROJ_DATA=${proj}/share/proj:<PATH2>:<PATH3> ? Can this solve your problem ?

[kidanger]

What about setting multiple paths like this PROJ_DATA=${proj}/share/proj:<PATH2>:<PATH3> ? Can this solve your problem ?

The issue is that the env variable is not even considered by pyproj, since it priorities internal_datadir over proj_lib_dirs/PROJ_DATA.

For a non-nix build of pyproj, the folder referenced by internal_datadir may not exist depending on how it was installed, in which case the user can use PROJ_DATA. For a nix build, this folder always exist, hence this PR.

[nixos-discourse]

This pull request has been mentioned on NixOS Discourse. There might be relevant details there:

https://discourse.nixos.org/t/week-in-geospatial-team/37035/6