如何使用“nix search”搜索 Haskell 包？

Question

我知道我可以使用 nix-env 搜索 Haskell 包

nix-env -f '<nixpkgs>' -qaP -A haskellPackages name_of_package

但这很慢而且没有缓存。如果我尝试使用新命令，nix search所有 Haskell 包都被隐藏。

$ nix search aeson
error: no results for the given search term(s)!

是否可以使用新nix search命令搜索 Haskell 包？如果是这样，如何？

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编辑：我在这个irc 日志中发现了一些关于这个的讨论，但我不太明白这些建议在实践中的含义。具体这部分：

20:49 <duairc> How do I make nix search include haskellPackages?
20:52 <ottidmes> duairc: you might try and call recurseIntoAttrs on haskellPackages
20:52 <rain1> thanks
20:52 <LnL> rain1: nix-env -f '<nixpkgs>' -qaP -A haskellPackages
20:54 <gchristensen> duairc: ^
20:54 <duairc> LnL: Thanks!
20:55 <LnL> err, wrong person
20:56 <LnL> you can also add an overlay that recurses, but that might make it
      hard to find non haskell stuff if you're searching for something else
20:56 <ottidmes> I can confirm that
      haskellPackages = super.recurseIntoAttrs super.haskellPackages; works though
20:58 <duairc> ottidmes: What do I do with that expression? Put it in
      configuration.nix somewhere? If I type "nix search ghcid" then
      will it find it?
20:59 <duairc> Ah, you're using super, so I guess it's an overlay
20:59 <clever> duairc: for `nix search` to find it, the overlay must be
      somewhere in $HOME, i forget the exact path
20:59 <clever> duairc: configuration.nix only effects nixos-rebuild and
      nothing else
21:00 <ottidmes> duairc: yeah, it should be put in your overlay that is
      also used by nix-env the like, so not nixpkgs.overlays in your
      configuration.nix as mentioned by clever, and then searching
      for e.g. nix search nix-diff will result in:
      * nixpkgs.haskellPackages.nix-diff (nix-diff)

Answer 1

根据 IRC 聊天，创建一个~/.config/nixpkgs/overlays.nix包含以下内容的文件：

[
  (self: super: {
    haskellPackages = super.recurseIntoAttrs super.haskellPackages;
  })
]

这是一个recurseForDerivations将 haskellPackages的属性设置为 true的叠加层。recurseForDerivations告诉 nix 工具遍历集合，在nix search. 它目前没有记录，但在此处实施。

在尼克斯维基描述了把覆盖和Nixpkgs手册介绍了什么是真正覆盖，以及如何使用它们。