1 files changed, 39 insertions, 0 deletions
diff --git a/nix/writeExecline/default.nix b/nix/writeExecline/default.nix
new file mode 100644
index 0000000000..5169b01386
--- /dev/null
+++ b/nix/writeExecline/default.nix
@@ -0,0 +1,39 @@
+{ 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 $0
+  # "env": don’t substitute, set # and 0…n environment vaariables, where n=$#
+  # "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 ''"${toString argMode}" is not a valid argMode, use one of "var", "var-full", "env", "none", "env-no-push".'';
+
+in
+depot.nix.writeScript name ''
+  #!${pkgs.execline}/bin/execlineb -W${env}
+  ${depot.nix.escapeExecline argList}
+''