Change formatting for ++, + and //

[Sereja313]

This commit implements a new formatting style for ++, + and //, like described in proposal 2 in the comment #228 (comment)

[github-actions]

Nixpkgs diff processing..

Will be available here

[infinisil]

(reviewed together with @Sereja313 in the meeting)

Problematic cases that are valid with the PR:

{
  foo = aaaaaaaaaaaaaaaaaaaaaaaaa
  + bbbbbbbbbbbbbbbbbbbbbbbbbbbbb
  + ccccccccccccccccccccccccccccc
  + ddddddddddddddddddddddddddddd;

  bar = "aaaaaaaaaaaaaaaaaaaaaaaa"
    + bbbbbbbbbbbbbbbbbbbbbbbbbbb
    + ccccccccccccccccccccccccccc
    + ddddddddddddddddddddddddddd;
}

{
  boot.kernelParams = [ aaaaaaaaaaaaaa ]
    ++ optionals config.boot.vesa [
      "vga=0x317"
      "nomodeset"
    ];
}

{
  foo = [ bar ]
    ++ baz;
}

Should address these, can use the above as tests.

[nixos-discourse]

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

https://discourse.nixos.org/t/formatting-team-meeting-2025-02-18/60511/1

[infinisil]

Oh and forgot to mention, we also need to update the standard document with this change.

[piegamesde]

Please don't. This is a strong violation of layers and really should be fixed earlier in the data flow

[Sereja313]

Yeah, it doesn't work anyway

[piegamesde]

If you want to remove the indentation, you need to move the nest calls wrapping absorbRHS into absorbRHS so that you can skip it for certain operations

To add context, your current code only works for cases where the first term gets absorbed into the line of the =, because then the nesting gets canceled. However, and I don't think those cases are currently sufficiently tested, you (probably?) also want stuff like this without indentation:

foo =
some function application that kinda is long
++ [
  a
  list
];

Also, don't forget to test cases where the = is indented, like

some.long.attribute # with a comment
  = [ stuff ]
  ++ more stuff;

[infinisil]

A bit messy notes from the meeting today:

{
  # PR
  # This example has additional indentation, so likely also has larger git diffs
  boot.kernelParams = [ aaaaaaaaaaaaaa ]
    ++ optionals config.boot.vesa [
      "vga=0x317"
      "nomodeset"
    ];

  # Base:
  boot.kernelParams = [ aaaaaaaaaaaaaa ];
  boot.kernelParams = [
    aaaaaaaaaaaaaa
    bbbbbbbbbbbbbb
  ];

  # Current
  # This example does not minimise git diff
  boot.kernelParams =
    [ aaaaaaaaaaaaaa ]
    ++ optionals config.boot.vesa [
      "vga=0x317"
      "nomodeset"
    ];
    
  # Alternative
  # This example minimises git diff
  boot.kernelParams = [
    aaaaaaaaaaaaaa
  ]
  ++ optionals config.boot.vesa [
    bbbbbbbbbbbbbb
  ];
}

• @MattSturgeon: The latter would be preferred for smaller diffs
• @infinisil: Can also be future work, as long as the PR doesn't make formatting worse, can merge it
• (doesn't block the treewide)
• @piegamesde can help out

[nixos-discourse]

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

https://discourse.nixos.org/t/formatting-team-meeting-2025-03-18/61868/1