The Nix Hour

Currently Playing: The Nix Hour #18 [fixed-points, makeExtensible, makeScope]

The Nix Hour is a weekly beginner-oriented improvised Q&A-style lecture on Nix, where you can bring your questions and we'll answer them with more context, examples, alternatives, tradeoffs and related topics. Feel free to ask questions using the live chat, or even ask questions directly by joining the meeting: https://meet.jit.si/nix-hour. Alternatively ask questions ahead of time by opening an issue in https://github.com/tweag/nix-hour For more information and updates, check out https://discourse.nixos.org/t/the-nix-hour-a-weekly-nix-qa-lecture-by-tweag/22767 00:00 Question: What's callPackage, newScope and makeScope? 01:20 A simple interdependent package set using pkgs.callPackage 04:42 Using a fixed-point function for less repetition 07:03 Making the package set extensible using lib.makeExtensible 12:55 Using makeScope and newScope for extending the nixpkgs scope 16:35 A potential approach of nesting your own packages to avoid accidental overrides 18:27 Changing how the default is passed 19:45 Further nesting scopes using makeScope 23:13 Cross-compilation with makeScopeWithSplicing 27:21 Overlaying using overrideScope, accidentally mixing up the argument ordering 30:49 makeScope overview 32:36 Question: How to not have all Nixpkgs packages in the callPackage scope? 34:42 Using makeExtensible to create a new empty callPackage scope 37:52 Using makeScope to create a new empty callPackage scope 42:37 Comparing the different scope approaches 45:48 Manually evaluating a fixed-point function 52:20 Using composeExtensions to compose two extensions into one