tests.nixpkgs-check-by-name: Add test for alternate callPackage's

Tests that alternate callPackage's don't give an error, so pkgs/by-name
is only required for pkgs.callPackage itself

pkgs/test/nixpkgs-check-by-name/tests/mock-nixpkgs.nix

@@ -30,7 +30,9 @@ let
   # The base fixed-point function to populate the resulting attribute set
   pkgsFun = self: {
     inherit lib;
-    callPackage = lib.callPackageWith self;
+    newScope = extra: lib.callPackageWith (self // extra);
+    callPackage = self.newScope { };
+    callPackages = lib.callPackagesWith self;
     someDrv = { type = "derivation"; };
   };
 

pkgs/test/nixpkgs-check-by-name/tests/only-callPackage-derivations/all-packages.nix

@@ -0,0 +1,16 @@
+self: super: {
+  alternateCallPackage = self.myScope.callPackage ({ myScopeValue, someDrv }:
+    assert myScopeValue;
+    someDrv
+  ) { };
+
+  myScope = self.lib.makeScope self.newScope (self: {
+    myScopeValue = true;
+  });
+
+  myPackages = self.callPackages ({ someDrv }: {
+    a = someDrv;
+    b = someDrv;
+  }) { };
+  inherit (self.myPackages) a b;
+}

pkgs/test/nixpkgs-check-by-name/tests/only-callPackage-derivations/default.nix

@@ -0,0 +1 @@
+import ../mock-nixpkgs.nix { root = ./.; }