Make callPackage observe <pkg>.override.argSelectors and by-name-overlay manage arg-selectors.nix and siblings

lib/customisation.nix

@@ -261,9 +261,14 @@ rec {
       f = if isFunction fn then fn else import fn;
       fargs = functionArgs f;
 
+      argSelectors = f.argSelectors or { };
+      selectedArgs = mapAttrs (_: select: select autoArgs) argSelectors;
+
+      customArgs = selectedArgs // args;
+
       # All arguments that will be passed to the function
       # This includes automatic ones and ones passed explicitly
-      allArgs = intersectAttrs fargs autoArgs // args;
+      allArgs = intersectAttrs fargs autoArgs // customArgs;
 
       # a list of argument names that the function requires, but
       # wouldn't be passed to it
@@ -278,7 +283,7 @@ rec {
       # Get a list of suggested argument names for a given missing one
       getSuggestions =
         arg:
-        pipe (autoArgs // args) [
+        pipe (autoArgs // customArgs) [
           attrNames
           # Only use ones that are at most 2 edits away. While mork would work,
           # levenshteinAtMost is only fast for 2 or less.
@@ -312,9 +317,20 @@ rec {
       # Only show the error for the first missing argument
       error = errorForArg (head (attrNames missingArgs));
 
+      result = makeOverridable f allArgs;
     in
     if missingArgs == { } then
-      makeOverridable f allArgs
+      if lib.isAttrs result then
+        result
+        // {
+          override =
+            result.override
+            // optionalAttrs (args == { }) {
+              inherit argSelectors;
+            };
+        }
+      else
+        result
     # This needs to be an abort so it can't be caught with `builtins.tryEval`,
     # which is used by nix-env and ofborg to filter out packages that don't evaluate.
     # This way we're forced to fix such errors in Nixpkgs,
@@ -353,9 +369,25 @@ rec {
       f = if isFunction fn then fn else import fn;
       auto = intersectAttrs (functionArgs f) autoArgs;
       mirrorArgs = mirrorFunctionArgs f;
-      origArgs = auto // args;
+
+      argSelectors = f.argSelectors or { };
+      selectedArgs = mapAttrs (_: select: select autoArgs) argSelectors;
+
+      customArgs = selectedArgs // args;
+      origArgs = auto // customArgs;
       pkgs = f origArgs;
-      mkAttrOverridable = name: _: makeOverridable (mirrorArgs (newArgs: (f newArgs).${name})) origArgs;
+      mkAttrOverridable =
+        name: _:
+        let
+          result = makeOverridable (mirrorArgs (newArgs: (f newArgs).${name})) origArgs;
+        in
+        if isAttrs result then
+          result
+          // {
+            override = result.override // optionalAttrs (args == { }) { inherit argSelectors; };
+          }
+        else
+          result;
     in
     if isDerivation pkgs then
       throw (
@@ -366,6 +398,19 @@ rec {
     else
       mapAttrs mkAttrOverridable pkgs;
 
+  makeCallPackageWithArgSelectors =
+    callPackage: fn: extraArgSelectors:
+    let
+      f = if isFunction fn then fn else import fn;
+      f' = if isAttrs f then f else mirrorFunctionArgs f f;
+    in
+    callPackage (
+      f'
+      // {
+        argSelectors = f.argSelectors or { } // extraArgSelectors;
+      }
+    ) { };
+
   /**
     Add attributes to each output of a derivation without changing
     the derivation itself and check a given condition when evaluating.

lib/default.nix

@@ -391,6 +391,7 @@ let
         makeOverridable
         callPackageWith
         callPackagesWith
+        makeCallPackageWithArgSelectors
         extendDerivation
         hydraJob
         makeScope

pkgs/top-level/by-name-overlay.nix

@@ -10,13 +10,20 @@ let
   lib = import ../../lib;
 
   inherit (builtins)
+    pathExists
     readDir
     ;
 
   inherit (lib.attrsets)
+    getAttrFromPath
     mapAttrs
     mapAttrsToList
     mergeAttrsList
+    optionalAttrs
+    ;
+
+  inherit (lib.customisation)
+    makeCallPackageWithArgSelectors
     ;
 
   # Package files for a single shard
@@ -49,6 +56,31 @@ self: super:
   # and whether it's defined by this file here or `all-packages.nix`.
   # TODO: This can be removed once `pkgs/by-name` can handle custom `callPackage` arguments without `all-packages.nix` (or any other way of achieving the same result).
   # Because at that point the code in ./stage.nix can be changed to not allow definitions in `all-packages.nix` to override ones from `pkgs/by-name` anymore and throw an error if that happens instead.
-  _internalCallByNamePackageFile = file: self.callPackage file { };
+  _internalCallByNamePackageFile =
+    file:
+    let
+      fArg = import file;
+      isSibling = fArg.type or null == "sibling";
+      fArg' =
+        if isSibling then
+          (
+            if fArg ? package then
+              self.${fArg.package}
+            else if fArg ? packagePath then
+              getAttrFromPath fArg.packagePath self
+            else
+              throw "${baseNameOf (dirOf file)}: expect `package' or `packagePath' in sibling metadata."
+          ).override
+        else
+          fArg;
+      transform = if isSibling && (fArg ? transform) then fArg.transform else { package, ... }: package;
+      package = makeCallPackageWithArgSelectors self.callPackage fArg' (
+        let
+          argSelectorsFile = "${toString (dirOf file)}/arg-selectors.nix";
+        in
+        optionalAttrs (pathExists argSelectorsFile) (import argSelectorsFile)
+      );
+    in
+    transform { inherit lib package; };
 }
 // mapAttrs (name: self._internalCallByNamePackageFile) packageFiles

pkgs/top-level/splice.nix

@@ -138,6 +138,8 @@ in
 
   callPackages = lib.callPackagesWith pkgsForCall;
 
+  callPackageWithArgSelectors = lib.makeCallPackageWithArgSelectors pkgs.callPackage;
+
   newScope = extra: lib.callPackageWith (pkgsForCall // extra);
 
   pkgs = if actuallySplice then splicedPackages // { recurseForDerivations = false; } else pkgs;