From f289d93a41cf9888f0ade3357b0d8df9104505dd Mon Sep 17 00:00:00 2001 From: Sandro Date: Tue, 5 Oct 2021 23:13:26 +0200 Subject: doc/contributing: add lib.optional (#121251) Co-authored-by: Cole Helbling --- doc/contributing/coding-conventions.chapter.md | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/doc/contributing/coding-conventions.chapter.md b/doc/contributing/coding-conventions.chapter.md index 85c8626bd99c..7a8e7741a330 100644 --- a/doc/contributing/coding-conventions.chapter.md +++ b/doc/contributing/coding-conventions.chapter.md @@ -181,6 +181,21 @@ rev = "${version}"; ``` +- Filling lists condionally _should_ be done with `lib.optional(s)` instead of using `if cond then [ ... ] else null` or `if cond then [ ... ] else [ ]`. + + ```nix + buildInputs = lib.optional stdenv.isDarwin iconv; + ``` + + instead of + + ```nix + buildInputs = if stdenv.isDarwin then [ iconv ] else null; + ``` + + As an exception, an explicit conditional expression with null can be used when fixing a important bug without triggering a mass rebuild. + If this is done a follow up pull request _should_ be created to change the code to `lib.optional(s)`. + - Arguments should be listed in the order they are used, with the exception of `lib`, which always goes first. ## Package naming {#sec-package-naming} -- cgit v1.2.3