Merge pull request #257100 from Ma27/version-info-lib

flake: fix `lib.trivial.version` when used from a flake

flake.nix

@@ -9,7 +9,8 @@
         nixpkgs = self;
       };
 
-      lib = import ./lib;
+      libVersionInfoOverlay = import ./lib/flake-version-info.nix self;
+      lib = (import ./lib).extend libVersionInfoOverlay;
 
       forAllSystems = lib.genAttrs lib.systems.flakeExposed;
     in
@@ -20,13 +21,7 @@
 
         nixosSystem = args:
           import ./nixos/lib/eval-config.nix (
-            args // {
-              modules = args.modules ++ [{
-                system.nixos.versionSuffix =
-                  ".${final.substring 0 8 (self.lastModifiedDate or self.lastModified or "19700101")}.${self.shortRev or "dirty"}";
-                system.nixos.revision = final.mkIf (self ? rev) self.rev;
-              }];
-            } // lib.optionalAttrs (! args?system) {
+            args // { inherit (self) lib; } // lib.optionalAttrs (! args?system) {
               # Allow system to be set modularly in nixpkgs.system.
               # We set it to null, to remove the "legacy" entrypoint's
               # non-hermetic default.
@@ -53,7 +48,11 @@
       # attribute it displays `omitted` instead of evaluating all packages,
       # which keeps `nix flake show` on Nixpkgs reasonably fast, though less
       # information rich.
-      legacyPackages = forAllSystems (system: import ./. { inherit system; });
+      legacyPackages = forAllSystems (system:
+        (import ./. { inherit system; }).extend (final: prev: {
+          lib = prev.lib.extend libVersionInfoOverlay;
+        })
+      );
 
       nixosModules = {
         notDetected = ./nixos/modules/installer/scan/not-detected.nix;

lib/flake-version-info.nix

@@ -0,0 +1,20 @@
+# This function produces a lib overlay to be used by the nixpkgs
+# & nixpkgs/lib flakes to provide meaningful values for
+# `lib.trivial.version` et al..
+#
+# Internal and subject to change, don't use this anywhere else!
+# Instead, consider using a public interface, such as this flake here
+# in this directory, `lib/`, or use the nixpkgs flake, which applies
+# this logic for you in its `lib` output attribute.
+
+self: # from the flake
+
+finalLib: prevLib: # lib overlay
+
+{
+  trivial = prevLib.trivial // {
+    versionSuffix =
+      ".${finalLib.substring 0 8 (self.lastModifiedDate or "19700101")}.${self.shortRev or "dirty"}";
+    revisionWithDefault = default: self.rev or default;
+  };
+}

lib/flake.nix

@@ -1,5 +1,10 @@
 {
   description = "Library of low-level helper functions for nix expressions.";
 
-  outputs = { self }: { lib = import ./.; };
+  outputs = { self }:
+    let
+      lib0 = import ./.;
+    in {
+      lib = lib0.extend (import ./flake-version-info.nix self);
+    };
 }

lib/trivial.nix

@@ -1,6 +1,18 @@
 { lib }:
 
-rec {
+let
+  inherit (lib.trivial)
+    isFunction
+    isInt
+    functionArgs
+    pathExists
+    release
+    setFunctionArgs
+    toBaseDigits
+    version
+    versionSuffix
+    warn;
+in {
 
   ## Simple (higher order) functions
 
@@ -439,7 +451,7 @@ rec {
   */
   functionArgs = f:
     if f ? __functor
-    then f.__functionArgs or (lib.functionArgs (f.__functor f))
+    then f.__functionArgs or (functionArgs (f.__functor f))
     else builtins.functionArgs f;
 
   /* Check whether something is a function or something