For NixOS evaluation, this gives a ~21% reduction in the number of values allocated and a ~4% speedup. It's also more readable.
		
			
				
	
	
		
			79 lines
		
	
	
		
			2.5 KiB
		
	
	
	
		
			Nix
		
	
	
	
	
	
			
		
		
	
	
			79 lines
		
	
	
		
			2.5 KiB
		
	
	
	
		
			Nix
		
	
	
	
	
	
/*
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Usage:
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  You define you custom builder script by adding all build steps to a list.
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  for example:
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       builder = writeScript "fsg-4.4-builder"
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               (textClosure [doUnpack addInputs preBuild doMake installPhase doForceShare]);
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  a step is defined by noDepEntry, fullDepEntry or packEntry.
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  To ensure that prerequisite are met those are added before the task itself by
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  textClosureDupList. Duplicated items are removed again.
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  See trace/nixpkgs/trunk/pkgs/top-level/builder-defs.nix for some predefined build steps
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  Attention:
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  let
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    pkgs = (import /etc/nixos/nixpkgs/pkgs/top-level/all-packages.nix) {};
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  in let
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    inherit (pkgs.stringsWithDeps) fullDepEntry packEntry noDepEntry textClosureMap;
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    inherit (pkgs.lib) id;
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    nameA = noDepEntry "Text a";
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    nameB = fullDepEntry "Text b" ["nameA"];
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    nameC = fullDepEntry "Text c" ["nameA"];
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    stages = {
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      nameHeader = noDepEntry "#! /bin/sh \n";
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      inherit nameA nameB nameC;
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    };
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  in
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    textClosureMap id stages
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    [ "nameHeader" "nameA" "nameB" "nameC"
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      nameC # <- added twice. add a dep entry if you know that it will be added once only [1]
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      "nameB" # <- this will not be added again because the attr name (reference) is used
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    ]
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  # result: Str("#! /bin/sh \n\nText a\nText b\nText c\nText c",[])
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  [1] maybe this behaviour should be removed to keep things simple (?)
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*/
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with import ./lists.nix;
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with import ./attrsets.nix;
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with import ./strings.nix;
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rec {
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  /* !!! The interface of this function is kind of messed up, since
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     it's way too overloaded and almost but not quite computes a
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     topological sort of the depstrings. */
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  textClosureList = predefined: arg:
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    let
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      f = done: todo:
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        if todo == [] then {result = []; inherit done;}
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        else
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          let entry = head todo; in
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          if isAttrs entry then
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            let x = f done entry.deps;
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                y = f x.done (tail todo);
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            in { result = x.result ++ [entry.text] ++ y.result;
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                 done = y.done;
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               }
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          else if done ? ${entry} then f done (tail todo)
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          else f (done // listToAttrs [{name = entry; value = 1;}]) ([predefined.${entry}] ++ tail todo);
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    in (f {} arg).result;
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  textClosureMap = f: predefined: names:
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    concatStringsSep "\n" (map f (textClosureList predefined names));
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  noDepEntry = text: {inherit text; deps = [];};
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  fullDepEntry = text: deps: {inherit text deps;};
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  packEntry = deps: {inherit deps; text="";};
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  stringAfter = deps: text: { inherit text deps; };
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}
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