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nixpkgs/pkgs/lib/strings-with-deps.nix
Marc Weber ea3688db98 added documentation illustrating behaviour of the new textClosureMap
implementation

svn path=/nixpkgs/trunk/; revision=15663
2009-05-19 23:26:08 +00:00

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Nix

/*
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 /etc/nixos/nixpkgs/pkgs/top-level/all-packages.nix) {};
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 (?)
*/
{stdenv, lib}:
with lib;
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 hasAttr entry done then f done (tail todo)
else f (done // listToAttrs [{name = entry; value = 1;}]) ([(builtins.getAttr entry predefined)] ++ 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="";};
# Old names - don't use. Will be removed soon. There are no more occurences in nixpkgs/nixos
FullDepEntry = fullDepEntry;
PackEntry = packEntry;
}