pkgs/profpatsch: WIP execline experiments

* runExecline: like runCommand, but a lot more lightweight
* symlink: symlink a given list of links together
* importer: a small DSL to “import” “modules” into a build context

Some highlights:
* runExecline does not use any stdenv (apart from the `execline` build)
* symlink uses netstrings to pass correct fields into the derivation
* no use of bash, everything uses execline.

1 files changed, 45 insertions, 0 deletions

diff --git a/pkgs/profpatsch/execline/importer.nix b/pkgs/profpatsch/execline/importer.nix
new file mode 100644
index 00000000..67464d17
--- /dev/null
+++ b/pkgs/profpatsch/execline/importer.nix
@@ -0,0 +1,45 @@
+{ lib, coreutils, s6-portable-utils, symlink }:
+let
+  example = {from, as, just, ...}:
+    [
+      (from coreutils [
+        (just "echo")
+        (as "core-ls" "ls")
+      ])
+      (from s6-portable-utils [
+        (as "ls" "s6-ls")
+        (just "s6-echo")
+      ])
+    ];
+
+  runImport = impsFn:
+    let
+      combinators = rec {
+        from = source: imports: {
+          inherit source imports;
+        };
+        as = newname: oldname: {
+          inherit oldname newname;
+        };
+        just = x: as x x;
+      };
+
+      # Drv -> As -> Symlink
+      toBin = module: {oldname, newname}: {
+        dest = "bin/${newname}";
+        orig = "${module}/bin/${oldname}";
+      };
+      # List (Import { source: Drv
+      #              , imports: List (As { oldname: String
+      #                                  , newname: String }))
+      # -> Drv
+      run = imps:
+        symlink "foo" (lib.concatLists
+          (map ({source, imports}:
+                   map (toBin source) imports)
+               imps));
+
+    # TODO: typecheck w/ newtypes
+    in run (impsFn combinators);
+
+in runImport example