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{ pkgs, lib, ... }:
# Write an execline script, represented as nested nix lists.
# Everything is escaped correctly.
# https://skarnet.org/software/execline/
# TODO(Profpatsch) upstream into nixpkgs
let
# replaces " and \ to \" and \\ respectively and quote with "
# e.g.
# a"b\c -> "a\"b\\c"
# a\"bc -> "a\\\"bc"
escapeExeclineArg = arg:
''"${builtins.replaceStrings [ ''"'' ''\'' ] [ ''\"'' ''\\'' ] (toString arg)}"'';
# Escapes an execline (list of execline strings) to be passed to execlineb
# Give it a nested list of strings. Nested lists are interpolated as execline
# blocks ({}).
# Everything is quoted correctly.
#
# Example:
# escapeExecline [ "if" [ "somecommand" ] "true" ]
# == ''"if" { "somecommand" } "true"''
escapeExecline = execlineList: lib.concatStringsSep " "
(let
go = arg:
if builtins.isString arg then [(escapeExeclineArg arg)]
else if builtins.isPath arg then [(escapeExeclineArg "${arg}")]
else if lib.isDerivation arg then [(escapeExeclineArg arg)]
else if builtins.isList arg then [ "{" ] ++ builtins.concatMap go arg ++ [ "}" ]
else abort "escapeExecline can only hande nested lists of strings, was ${lib.generators.toPretty {} arg}";
in builtins.concatMap go execlineList);
in
name:
{
# "var": substitute readNArgs variables and start $@
# from the (readNArgs+1)th argument
# "var-full": substitute readNArgs variables and start $@ from $0
# "env": don’t substitute, set # and 0…n environment vaariables, where n=$#
# "none": don’t substitute or set any positional arguments
# "env-no-push": like "env", but bypass the push-phase. Not recommended.
argMode ? "var",
# Number of arguments to be substituted as variables (passed to "var"/"-s" or "var-full"/"-S"
readNArgs ? 0,
}:
# Nested list of lists of commands.
# Inner lists are translated to execline blocks.
argList:
let
env =
if argMode == "var" then "s${toString readNArgs}"
else if argMode == "var-full" then "S${toString readNArgs}"
else if argMode == "env" then ""
else if argMode == "none" then "P"
else if argMode == "env-no-push" then "p"
else abort ''"${toString argMode}" is not a valid argMode, use one of "var", "var-full", "env", "none", "env-no-push".'';
in
# TODO(Profpatsch): rewrite `writeScript` with `runExecline`
pkgs.writeScript name ''
#!${pkgs.execline}/bin/execlineb -W${env}
${escapeExecline argList}
''
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