depot/third_party/tvl/nix/writeExecline/default.nix

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{ pkgs, depot, ... }:
# Write an execline script, represented as nested nix lists.
# Everything is escaped correctly.
# https://skarnet.org/software/execline/
# TODO(Profpatsch) upstream into nixpkgs
name:
{
# "var": substitute readNArgs variables and start $@
# from the (readNArgs+1)th argument
# "var-full": substitute readNArgs variables and start $@ from $0
# "env": dont substitute, set # and 0…n environment vaariables, where n=$#
# "none": dont 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 ''"${toString argMode}" is not a valid argMode, use one of "var", "var-full", "env", "none", "env-no-push".'';
in
depot.nix.writeScript name ''
#!${pkgs.execline}/bin/execlineb -W${env}
${depot.nix.escapeExecline argList}
''