feat: make importing the std library optional

.github/workflows/test.yml

@@ -7,11 +7,18 @@ jobs:
       - uses: actions/checkout@v4
       - uses: nixbuild/nix-quick-install-action@v28
       - name: Structural Integirty Test
-        run: cd test && ./bld.sh
+        run: cd test/integrity && ./bld.sh
   format:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
       - uses: nixbuild/nix-quick-install-action@v28
       - name: Code Format Check
         run: eval "$(nix print-dev-env -f shell.nix)" && treefmt --fail-on-change
+  std-config:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: nixbuild/nix-quick-install-action@v28
+      - name: Std Library Config Test
+        run: cd test/std-import && ./import.sh > /dev/null

compose.toml

@@ -0,0 +1,3 @@
+[std]
+use = true
+nixpkgs_lib = false

default.nix

@@ -1,9 +1,11 @@
 let
   src = import ./src;
   l = builtins;
+  pins = import ./npins;
 in
 {
   extern ? { },
+  config ? builtins.fromTOML (builtins.readFile ./compose.toml),
 }:
 dir:
 with src;
@@ -20,20 +22,38 @@ let
 
       contents = l.readDir dir;
 
-      scope = injectPrevious pre {
-        inherit std;
-        atom = atom';
-        mod = self';
-        builtins = errors.builtins;
-        import = errors.import;
-        scopedImport = errors.import;
-        __fetchurl = errors.fetch;
-        __currentSystem = errors.system;
-        __currentTime = errors.time;
-        __nixPath = errors.nixPath;
-        __storePath = errors.storePath;
+      preOpt = {
+        _if = pre != null;
+        inherit pre;
       };
 
+      scope =
+        injectOptionals
+          {
+            atom = atom';
+            mod = self';
+            builtins = errors.builtins;
+            import = errors.import;
+            scopedImport = errors.import;
+            __fetchurl = errors.fetch;
+            __currentSystem = errors.system;
+            __currentTime = errors.time;
+            __nixPath = errors.nixPath;
+            __storePath = errors.storePath;
+          }
+          [
+            preOpt
+            {
+              _if = config.std.use or false;
+              std =
+                std
+                // cond {
+                  _if = config.std.nixpkgs_lib or false;
+                  lib = import "${pins."nixpkgs.lib"}/lib";
+                };
+            }
+          ];
+
       Import = scopedImport scope;
 
       g =
@@ -43,7 +63,7 @@ let
           file = parse name;
         in
         if type == "directory" then
-          { ${name} = f (injectPrevious pre (lowerKeys self)) path; }
+          { ${name} = f ((lowerKeys self) // cond preOpt) path; }
         else if type == "regular" && file.ext or null == "nix" && name != "mod.nix" then
           { ${file.name} = Import "${path}"; }
         else

npins/sources.json

@@ -5,6 +5,18 @@
       "name": "nixpkgs-unstable",
       "url": "https://releases.nixos.org/nixpkgs/nixpkgs-24.11pre660607.c3392ad349a5/nixexprs.tar.xz",
       "hash": "1g2p74w085252qbxjymrzzccd203bfwxh8sbcyvbzan6bgqfvwi1"
+    },
+    "nixpkgs.lib": {
+      "type": "Git",
+      "repository": {
+        "type": "GitHub",
+        "owner": "nix-community",
+        "repo": "nixpkgs.lib"
+      },
+      "branch": "master",
+      "revision": "8bebd4c74f368aacb047f0141db09ec6b339733c",
+      "url": "https://github.com/nix-community/nixpkgs.lib/archive/8bebd4c74f368aacb047f0141db09ec6b339733c.tar.gz",
+      "hash": "0vzy9hs0k8zi9h4lx1krq578j3wdc62d6g4hddxj9sfkdmz8r3bn"
     }
   },
   "version": 3

src/default.nix

@@ -55,13 +55,7 @@ in
              ${toString dir}/mod.nix
     '';
 
-  injectPrevious =
-    pre: set:
-    set
-    // cond {
-      _if = pre != null;
-      inherit pre;
-    };
+  injectOptionals = builtins.foldl' (acc: x: acc // cond x);
 
   hasMod = contents: contents."mod.nix" or null == "regular";
 }

test/common.sh

@@ -0,0 +1,7 @@
+should_fail () {
+  if "$@" 2> /dev/null; then
+    exit 1
+  else
+    true
+  fi
+}

test/bld.nix → test/integrity/bld.nix

@@ -1,5 +1,5 @@
 let
-  compose = import ../.;
+  compose = import ../../.;
   mod = compose { } (
     # added to test implicit path conversion when path is a string
     builtins.toPath ./bld

test/std-import/import.nix

@@ -0,0 +1,15 @@
+let
+  compose = set: (import ../../.) set ./import;
+in
+{
+  default = compose { };
+  noStd = compose { config.std.use = false; };
+  withNixpkgsLib = compose {
+    config.std.nixpkgs_lib = true;
+    config.std.use = true;
+  };
+  noStdNixpkgs = compose {
+    config.std.nixpkgs_lib = true;
+    config.std.use = false;
+  };
+}

test/std-import/import.sh

@@ -0,0 +1,21 @@
+#!/usr/bin/env bash
+
+set -ex
+
+. ../common.sh
+
+# defaults
+nix eval -f import.nix default.std
+should_fail nix eval -f import.nix default.lib
+
+# no std set
+should_fail nix eval -f import.nix noStd.std
+should_fail nix eval -f import.nix noStd.lib
+
+# no std set
+nix eval -f import.nix withNixpkgsLib.std
+nix eval -f import.nix withNixpkgsLib.lib
+
+# no std set
+should_fail nix eval -f import.nix noStdNixpkgs.std
+should_fail nix eval -f import.nix noStdNixpkgs.lib

test/std-import/import/mod.nix

@@ -0,0 +1,4 @@
+{
+  Std = std;
+  Lib = std.lib;
+}