This was derived from
else if (c1 == "" && n2) return true; // true implies c1 < n2
However, this has no effect since Word always looses out against Number
anyways and the `pre` rules are also unaffected by this change – since
this only affects comparison of an empty Word part with a Number.
Change-Id: Ia04e42ac726352b688c87674b0fdb355f06edbcb
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6722
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
This is necessary because builtins.compareVersions compares versions in
a subtly not-quite-but-still-lexicographical way: `pre` for example can
have an effect if it is post-fixed: `2.3 < 2.3pre`. This is a violation
of the rule that in a lexicographical ordering, the longer string is
considered greater if they are otherwise equal. builtins.compareVersion
is comparing lexicographically though, if you do the following
transformation beforehand:
2.3 --split--> [ "2" "3" ] --append--> [ "2" "3" "" ]
2.3pre --split--> [ "2" "3" "pre" ] --append--> [ "2" "3" "pre" "" ]
Comparing the transformed version is then done lexicographically:
2.3 < 2.3.0pre since [ "2" "3" "" ] < [ "2" "3" "0" "pre" ]
Here, the `pre` rule never comes into effect because no comparison on it
happens, instead we use the longer string rule of a lexicographical
comparison.
In the C++ codebase, the reason for this behavior is that the
iterator-esque construct they use always yields the empty string before
it exposes it has been fully consumed. This is probably intentional to
support the postfixed `pre` which is, for example, used by NixOS
versions (e.g. unstable post 22.05 is 22.11-pre). We replicate this
behavior using the `Chain` iterator in `VersionPartsIter::new_for_cmp`.
Change-Id: I021c69aa27b0b7deb949dffe50ed18b6de3a7b1f
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6720
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
This is based on the [relevant code] in C++ Nix. Our version has more
branches because the C++ one only checks if it is less than or not, so
can save handling a few cases. We on the other hand, can avoid calling
the algorithm twice. It'd be nice to implement proptests for this in the
future and to make sure that this weird little algorithm doesn't violate
the Ord laws.
[relevant code]: cd35bbbeef/src/libstore/names.cc (L81-L94)
Change-Id: I46642e6da5eac7c0883cdce860622cdba04cd12b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6719
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
