Add nixredo-whichdo; Put do file discovery into nix

builder.nix

@@ -1,32 +1,42 @@
-builderArgs:
+buildArgs@{ lib ? import ./lib.nix {}, nixpkgs ? <nixpkgs>, pkgs ? import nixpkgs {} }:
 let
+  inherit (lib) searchPath whichdo d1 d2;
 
-  myself = { nixpkgs ? <nixpkgs>, pkgs ? import nixpkgs {}, rargs, cwd }:
-    builder:
+  resolve = path: let
+    builder = (whichdo path);
+    in if builder == "" then throw "No rule to build ${path}"
+       else runBuilder (d1 path builder) (d2 path builder) builder;
+
+  runBuilder = d1: d2: builder:
+    with pkgs.lib;
     with builtins;
     let
-      resolveLocal = arg: let
-        fullPath = cwd + "/" + arg + ".nix";
-        recurse = myself { rargs = [ (toString arg) (toString arg) ]; inherit cwd; };
-      in recurse fullPath;
-      funcPkgs = { __functor = self: arg: resolveLocal arg; } // pkgs;
+      # Funktionalise pkgs; our main entry point to resolve default*nix build scripts.
+      funcPkgs = { __functor = self: arg: resolve arg; } // pkgs;
 
-      _builder = if (tryEval (import builder)).success
-                 then import builder
-                 else ''
-         #!/bin/sh
-         ${builder} $1 $2 $out >$out
-       '';
+      _builder = if (tryEval (let
+        # Needs to be done as nix chokes on empty files rn.
+        content = readFile builder;
+      in assert content != "" && (! (hasPrefix "#!" content)); import builder)).success
+                  then import builder
+                  else ''
+                    #!/bin/sh
+                    ${/. + builder} $d1 $d2 $out >$out
+                  '';
       __builder = if isFunction _builder then _builder funcPkgs
                   else _builder;
+
       args = { stdenv = pkgs.stdenvNoCC; } // (if isString __builder
-                                               then { builder = __builder; }
-                                               else  __builder);
-    in (args.deriver or args.stdenv.mkDerivation) ({
-      name = pkgs.lib.strings.sanitizeDerivationName (builtins.elemAt rargs 0);
-      buildCommand = args.builder;
-      passAsFile = [ "buildCommand" ];
-      preferLocalBuild = true;
-      allowSubstitutes = false;
-    } // (removeAttrs args [ "builder" "system" "deriver" "stdenv" ])); # myself
-in myself builderArgs
+                                                then { builder = __builder; }
+                                                else  __builder);
+
+      drv = (args.deriver or args.stdenv.mkDerivation) ({
+        name = pkgs.lib.strings.sanitizeDerivationName d1;
+        buildCommand = args.builder;
+        passAsFile = [ "buildCommand" ];
+        preferLocalBuild = true;
+        allowSubstitutes = false;
+        inherit d1 d2;
+      } // (removeAttrs args [ "builder" "system" "deriver" "stdenv" ]));
+    in drv; # myself
+in resolve

default.nix

@@ -5,10 +5,13 @@ stdenv.mkDerivation {
   phases = [ "installPhase" "fixupPhase" ];
   jq = "${jq}/bin/jq";
   buildernix = ./builder.nix;
+  libnix = ./lib.nix;
+
+  files = [ ./nixredo ./nixredo-deps ./nixredo-whichdo ];
 
   installPhase = ''
     mkdir -p $out/bin
-    for f in ${./nixredo} ${./nixredo-deps}; do
+    for f in $files; do
       _f=$out/bin/nixredo''${f##*-nixredo}
       cp $f $_f
       substituteAllInPlace $_f

lib.nix

@@ -0,0 +1,54 @@
+{ lib ? import <nixpkgs/lib> }:
+let
+  inherit (builtins) length genList pathExists;
+  inherit (lib) take splitString concatStringsSep last foldl foldr head
+  tail singleton removePrefix hasSuffix removeSuffix flatten crossLists reverseList;
+  butlast = list: take (length list - 1) list;
+  dirname = path: let _p = (butlast (splitString "/" path)); in if _p != [] then concatStringsSep "/" _p else "./";
+  basename = path: (last (splitString "/" path));
+
+  doFileSuffix = "do";
+
+  genPatterns = path: let
+    fn = basename path;
+  in (map (x: "default." + x)
+       (foldr (a: b: let x = (head b); in [ (a + "." + x) ] ++ b)
+         [ doFileSuffix ]
+         (tail (splitString "." fn))));
+
+  searchPath = path:
+    let
+      pathlist = (splitString "/" path);
+      pat = (last pathlist);
+      doFile = path + "." + doFileSuffix;
+      patlist = genPatterns pat;
+      foldedpaths = foldr (a: b:
+        let
+          h = if length b == 0 then "" else head b;
+        in [ (h + a + "/") ] ++ b) [] (tail (reverseList pathlist));
+      pths = crossLists (p: pat: p + pat) [ foldedpaths patlist ];
+    in [ doFile ] ++ pths;
+
+  cwd = "/home/spacefrogg/tmp";
+  path = cwd + "/foo/bar/baz.def.c";
+
+  whichdo = path: let
+    pathlist = searchPath path;
+  in foldl (res: p: if res == "" then if pathExists p then p else res else res) "" pathlist;
+
+  d1 = path: pat: let
+    dir = (dirname pat) + "/";
+  in removePrefix dir path;
+
+  d2 = path: pat: let
+    dir = (dirname pat) + "/";
+    _path = removePrefix dir path;
+    _pat = removeSuffix ".${doFileSuffix}" (removePrefix "${dir}default" pat);
+    _out = removeSuffix _pat _path;
+  in if _out == "" then _path else _out;
+
+  self = {
+    inherit dirname basename searchPath cwd path doFileSuffix whichdo d1 d2;
+  };
+
+in self

nixredo

@@ -2,25 +2,18 @@
 exec >&2
 [ "${NIXREDO_ROOT-x}" != x ] || { printf "Set NIXREDO_ROOT. Set empty to use global nix store\n"; exit 127; }
 if [ $# -eq 0 ]; then set -- all; fi
-if [ -e "$1.nix" ]; then
-  set -e
-  set -- "$1" "$1" "$1.redo.tmp"
-  f=$(realpath "$1.nix")
-  out=$(nix -vL --show-trace build ${NIXREDO_ROOT:+--store "$NIXREDO_ROOT"} \
-            --option auto-optimise-store true --option substituters daemon \
-            --impure --json --no-link \
-            --expr "import @buildernix@ { cwd = \"$PWD/\"; rargs = [ \"$1\" \"$1\" ];} \"$f\"" |
-            @jq@ -r '.[0].outputs.out')
-  [ -n "$out" ] || exit 127
-  rm -rf "$3"
-  ln -s "${NIXREDO_ROOT+$NIXREDO_ROOT}$out" "$3"
-  # ln "${NIXREDO_ROOT+$NIXREDO_ROOT/}$out" "$3"
-  # chmod +w "$3"
-  # touch "$3"
-  mv "$3" "$1"
-elif [ -e "$1" ]; then
-  :
-else
-  printf "Error: No rule to build %s\n" "$1"
-  exit 127
-fi
+set -e
+set -- "$1" "$1" "$1.redo.tmp"
+f=$(realpath -s "$1")
+out=$(nix -vL --show-trace build ${NIXREDO_ROOT:+--store "$NIXREDO_ROOT"} \
+          --option auto-optimise-store true --option substituters daemon \
+          --impure --json --no-link \
+          --expr " import @buildernix@ { lib = import @libnix@ {}; } \"$f\"" |
+          @jq@ -r '.[0].outputs.out')
+[ -n "$out" ] || exit 127
+rm -rf "$3"
+ln -s "${NIXREDO_ROOT+$NIXREDO_ROOT}$out" "$3"
+# ln "${NIXREDO_ROOT+$NIXREDO_ROOT/}$out" "$3"
+# chmod +w "$3"
+# touch "$3"
+mv "$3" "$1"

nixredo-whichdo

@@ -0,0 +1,3 @@
+#!/bin/sh
+f=$(realpath -s "$1")
+nix eval --impure --expr "with import @libnix@ {}; /. + (whichdo \"$f\")"