List all packages filtered by some maintainer

all-packages-of-a-maintainer.nix

#usage: 
# nix-instantiate --arg maintainer "\"Matthias Beyer <mail@beyermatthias.de>\"" --strict --json --eval ./all-packages-of-a-maintainer.nix | $(nix-build '<nixpkgs>' -A jq)/bin/jq

with (import <nixpkgs> {});
with lib;

{ maintainer }:
let 
  filter = k: v: 
  let
    evalResult = builtins.tryEval (
      if (builtins.typeOf v) == "set" && (builtins.hasAttr "meta" v) && (builtins.hasAttr "maintainers" v.meta) 
      then if (builtins.typeOf v.meta.maintainers) == "list"
           then
             builtins.elem maintainer v.meta.maintainers
           else if builtins.typeOf v.meta.maintainers == "string"
                then v.meta.maintainers == maintainer
                else false
      else false
    );
  in
    if evalResult.success 
    then evalResult.value
    else false;
in
filterAttrs filter pkgs