1 files changed, 84 insertions, 0 deletions
diff --git a/lib/strings-with-deps.nix b/lib/strings-with-deps.nix
new file mode 100644
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+++ b/lib/strings-with-deps.nix
@@ -0,0 +1,84 @@
+{ lib }:
+/*
+Usage:
+
+  You define you custom builder script by adding all build steps to a list.
+  for example:
+       builder = writeScript "fsg-4.4-builder"
+               (textClosure [doUnpack addInputs preBuild doMake installPhase doForceShare]);
+
+  a step is defined by noDepEntry, fullDepEntry or packEntry.
+  To ensure that prerequisite are met those are added before the task itself by
+  textClosureDupList. Duplicated items are removed again.
+
+  See trace/nixpkgs/trunk/pkgs/top-level/builder-defs.nix for some predefined build steps
+
+  Attention:
+
+  let
+    pkgs = (import <nixpkgs>) {};
+  in let
+    inherit (pkgs.stringsWithDeps) fullDepEntry packEntry noDepEntry textClosureMap;
+    inherit (pkgs.lib) id;
+
+    nameA = noDepEntry "Text a";
+    nameB = fullDepEntry "Text b" ["nameA"];
+    nameC = fullDepEntry "Text c" ["nameA"];
+
+    stages = {
+      nameHeader = noDepEntry "#! /bin/sh \n";
+      inherit nameA nameB nameC;
+    };
+  in
+    textClosureMap id stages
+    [ "nameHeader" "nameA" "nameB" "nameC"
+      nameC # <- added twice. add a dep entry if you know that it will be added once only [1]
+      "nameB" # <- this will not be added again because the attr name (reference) is used
+    ]
+
+  # result: Str("#! /bin/sh \n\nText a\nText b\nText c\nText c",[])
+
+  [1] maybe this behaviour should be removed to keep things simple (?)
+*/
+
+let
+  inherit (lib)
+    concatStringsSep
+    head
+    isAttrs
+    listToAttrs
+    tail
+    ;
+in
+rec {
+
+  /* !!! The interface of this function is kind of messed up, since
+     it's way too overloaded and almost but not quite computes a
+     topological sort of the depstrings. */
+
+  textClosureList = predefined: arg:
+    let
+      f = done: todo:
+        if todo == [] then {result = []; inherit done;}
+        else
+          let entry = head todo; in
+          if isAttrs entry then
+            let x = f done entry.deps;
+                y = f x.done (tail todo);
+            in { result = x.result ++ [entry.text] ++ y.result;
+                 done = y.done;
+               }
+          else if done ? ${entry} then f done (tail todo)
+          else f (done // listToAttrs [{name = entry; value = 1;}]) ([predefined.${entry}] ++ tail todo);
+    in (f {} arg).result;
+
+  textClosureMap = f: predefined: names:
+    concatStringsSep "\n" (map f (textClosureList predefined names));
+
+  noDepEntry = text: {inherit text; deps = [];};
+  fullDepEntry = text: deps: {inherit text deps;};
+  packEntry = deps: {inherit deps; text="";};
+
+  stringAfter = deps: text: { inherit text deps; };
+
+}