【问题标题】：nix function to merge attributes / records recursively and concatenate arraysnix 函数以递归方式合并属性/记录并连接数组
【发布时间】：2019-02-03 15:57:39
【问题描述】：

有人知道合并记录列表的功能吗

如果要合并的所有值都是记录 - 递归合并它们
如果要合并的所有值都是数组 - 连接数组
如果无法合并值 - 首选后一个值

示例 1：

recursiveMergeAttrs [
  { a = "x"; c = "m"; list = [1]; }
  { a = "y"; b = "z"; list = [2]; }
]

returns

{ a = "y"; b = "z"; c="m"; list = [1 2] }

示例 2

recursiveMergeAttrs [
  {
    boot.loader.grub.enable = true;
    boot.loader.grub.device = "/dev/hda";
  }
  {
    boot.loader.grub.device = "";
  }
]

returns

{
  boot.loader.grub.enable = true;
  boot.loader.grub.device = "";
}

附言

recursiveUpdate 不工作

recursiveMergeAttrs = listOfAttrsets: lib.fold (attrset: acc: lib.recursiveUpdate attrset acc) {} listOfAttrsets

recursiveMergeAttrs [ { a = "x"; c = "m"; list = [1]; } { a = "y"; b = "z"; list = [2]; } ]

returns 

{ a = "y"; b = "z"; c = "m"; list = [ 2 ]; }

【问题讨论】：

标签： nix

【解决方案1】：

做到了

{ lib, ... }:

with lib;

/*
  Merges list of records, concatenates arrays, if two values can't be merged - the latter is preferred

  Example 1:
    recursiveMerge [
      { a = "x"; c = "m"; list = [1]; }
      { a = "y"; b = "z"; list = [2]; }
    ]

    returns

    { a = "y"; b = "z"; c="m"; list = [1 2] }

  Example 2:
    recursiveMerge [
      {
        a.a = [1];
        a.b = 1;
        a.c = [1 1];
        boot.loader.grub.enable = true;
        boot.loader.grub.device = "/dev/hda";
      }
      {
        a.a = [2];
        a.b = 2;
        a.c = [1 2];
        boot.loader.grub.device = "";
      }
    ]

    returns

    {
      a = {
        a = [ 1 2 ];
        b = 2;
        c = [ 1 2 ];
      };
      boot = {
        loader = {
          grub = {
            device = "";
            enable = true;
          };
        };
      };
    } 


*/

let

recursiveMerge = attrList:
  let f = attrPath:
    zipAttrsWith (n: values:
      if tail values == []
        then head values
      else if all isList values
        then unique (concatLists values)
      else if all isAttrs values
        then f (attrPath ++ [n]) values
      else last values
    );
  in f [] attrList;


in

recursiveMerge

【讨论】：