Merge pull request #167947 from MatthewCroughan/mc/callLocklessFlake

lib: add callLocklessFlake

lib/default.nix

@@ -11,6 +11,9 @@ let
     callLibs = file: import file { lib = self; };
   in {
 
+    # interacting with flakes
+    flakes = callLibs ./flakes.nix;
+
     # often used, or depending on very little
     trivial = callLibs ./trivial.nix;
     fixedPoints = callLibs ./fixed-points.nix;
@@ -59,6 +62,7 @@ let
     # linux kernel configuration
     kernel = callLibs ./kernel.nix;
 
+    inherit (self.flakes) callLocklessFlake;
     inherit (builtins) add addErrorContext attrNames concatLists
       deepSeq elem elemAt filter genericClosure genList getAttr
       hasAttr head isAttrs isBool isInt isList isString length

lib/flakes.nix

@@ -0,0 +1,22 @@
+{ lib }:
+
+rec {
+
+  /* imports a flake.nix without acknowledging its lock file, useful for
+    referencing subflakes from a parent flake. The second argument allows
+    specifying the inputs of this flake.
+
+    Example:
+      callLocklessFlake {
+        path = ./directoryContainingFlake;
+        inputs = { inherit nixpkgs; };
+      }
+  */
+  callLocklessFlake = { path, inputs ? { } }:
+    let
+      self = { outPath = path; } //
+        ((import (path + "/flake.nix")).outputs (inputs // { self = self; }));
+    in
+    self;
+
+}

lib/tests/flakes/subflakeTest/flake.nix

@@ -0,0 +1,8 @@
+{
+  outputs = { self, subflake, callLocklessFlake }: rec {
+    x = (callLocklessFlake {
+      path = subflake;
+      inputs = {};
+    }).subflakeOutput;
+  };
+}

lib/tests/flakes/subflakeTest/subflake/flake.nix

@@ -0,0 +1,5 @@
+{
+  outputs = { self }: {
+    subflakeOutput = 1;
+  };
+}

lib/tests/misc.nix

@@ -22,6 +22,15 @@ in
 
 runTests {
 
+# FLAKES
+
+  testCallLocklessFlake = {
+    expr = callLocklessFlake {
+      path = ./flakes/subflakeTest;
+      inputs = { subflake = ./flakes/subflakeTest/subflake; inherit callLocklessFlake; };
+    };
+    expected = { x = 1; outPath = ./flakes/subflakeTest; };
+  };
 
 # TRIVIAL