pkgs/profpatsch/runExecline: move to list

We can auto-escape execlines correctly if we model them as nix-style
lists, so we shoud certainly do so. It also helps abstraction.

1 files changed, 30 insertions, 0 deletions

diff --git a/pkgs/profpatsch/execline/escape.nix b/pkgs/profpatsch/execline/escape.nix
new file mode 100644
index 00000000..d9a0be0c
--- /dev/null
+++ b/pkgs/profpatsch/execline/escape.nix
@@ -0,0 +1,30 @@
+{ lib }:
+let
+  # replaces " and \ to \" and \\ respectively and quote with "
+  # e.g.
+  #   a"b\c -> "a\"b\\c"
+  #   a\"bc -> "a\\\"bc"
+  # TODO upsteam into nixpkgs
+  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 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 {
+  inherit escapeExecline;
+}