From 6d84d6bdc1904b1afeecac4ee3fb492966fc882a Mon Sep 17 00:00:00 2001 From: Jade Lovelace Date: Wed, 15 May 2024 21:40:39 -0700 Subject: builtins: fix builtins.langVersion docs to state it's deprecated This builtin was always a problem and nixpkgs uses it in exactly one place, to give up if the Nix version is absurdly old. It has no other use cases, and doesn't work in a multi-implementation world anyway. Change-Id: I03c36e118591029e2ef14b091fe14a311c66a08a --- src/libexpr/primops.cc | 29 ++++++++++++++++++++--------- 1 file changed, 20 insertions(+), 9 deletions(-) (limited to 'src/libexpr/primops.cc') diff --git a/src/libexpr/primops.cc b/src/libexpr/primops.cc index 33a2688f1..e36b800c3 100644 --- a/src/libexpr/primops.cc +++ b/src/libexpr/primops.cc @@ -4355,10 +4355,13 @@ void EvalState::createBaseEnv() .doc = R"( Legacy version of Nix. Always returns "2.18.3-lix" on Lix. - To determine if features exist, Nix scripts should instead use direct - means of feature detection, such as checking for existence of - builtins they want to use. Doing so allows for much better compatibility - across implementations. + Code in the Nix language should use other means of feature detection + like detecting the presence of builtins, rather than trying to find + the version of the Nix implementation, as there may be other Nix + implementations with different feature combinations. + + If the feature you want to write compatibility code for cannot be + detected by any means, please file a Lix bug. )", }); @@ -4377,15 +4380,23 @@ void EvalState::createBaseEnv() )", }); - /* Language version. This should be increased every time a new - language feature gets added. It's not necessary to increase it - when primops get added, because you can just use `builtins ? - primOp' to check. */ + /* Legacy language version. + * This is fixed at 6, and will never change in the future on Lix. + * A better language versioning construct needs to be built instead. */ v.mkInt(6); addConstant("__langVersion", v, { .type = nInt, .doc = R"( - The current version of the Nix language. + The legacy version of the Nix language. Always is `6` on Lix, + matching Nix 2.18. + + Code in the Nix language should use other means of feature detection + like detecting the presence of builtins, rather than trying to find + the version of the Nix implementation, as there may be other Nix + implementations with different feature combinations. + + If the feature you want to write compatibility code for cannot be + detected by any means, please file a Lix bug. )", }); -- cgit v1.2.3