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https://github.com/NixOS/nixpkgs.git
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afa6c51f27
Nix can perform static scope checking, but whenever code is inside a `with` expression, the analysis breaks down, because it can't know statically what's in the attribute set whose attributes were brought into scope. In those cases, Nix has to assume that everything works out. Except it doesnt. Removing `with` from lib/ revealed an undefined variable in an error message. If that doesn't convince you that we're better off without `with`, I can tell you that this PR results in a 3% evaluation performance improvement because Nix can look up local variables by index. This adds up with applications like the module system. Furthermore, removing `with` makes the binding site of each variable obvious, which helps with comprehension.
85 lines
2.5 KiB
Nix
85 lines
2.5 KiB
Nix
{ lib }:
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/*
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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 <nixpkgs>) {};
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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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let
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inherit (lib)
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concatStringsSep
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head
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isAttrs
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listToAttrs
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tail
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;
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in
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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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