The default value for the setting was evaluated by
calling a method on the object _being currently constructed_,
so we were using it before all fields were initialized.
This has been fixed by making the called method static,
and not using the previously used fields at all.
But functionality hasn't changed!
The fields were usually always zero (by chance?) anyway,
meaning the conditional path was always taken.
Thus the current logic has been kept, the code simplified,
and UB removed.
This was found with the helper of UBSan.
Splitting it out immediately answers questions like [this],
without increasing the number of compilation units.
I did consider using boost::hash_combine instead, but it doesn't seem
to be quite as capable, accepting only two arguments.
[this]: https://github.com/NixOS/nix/pull/11113#discussion_r1679991573
This makes it possible to certain discern failures from empty
snippets, which I think is an ok review comment.
Maybe it should do so for swapped column indexes too, but I'm not
sure.
I don't think it matters in the grand scheme. We don't even have
a real use case for `nullopt` now anyway.
Since we don't have a use case, I'm not applying this logic to
higher level functions yet.
Unfortunately these don't render correctly, because they go into the
markdown renderer, instead of the terminal.
```
nix-repl> :doc lib.version
Attribute '[35;1mversion[0m'
… defined at [35;1m/home/user/h/nixpkgs/lib/default.nix:73:40[0m
```
We could switch that to go direct to the terminal, but then we should
do the same for the primops, to get a consistent look.
Reverting for now.
This reverts commit 3413e0338cbee1c7734d5cb614b5325e51815cde.
... at call sites that are may be in the hot path.
I do not know how clever the compiler gets at these sites.
My primary concern is to not regress performance and I am confident
that this achieves it the easy way.
Known behavior changes:
- `MemorySourceAccessor`'s comparison operators no longer forget to
compare the `SourceAccessor` base class.
Progress on #10832
What remains for that issue is hopefully much easier!
- Fix eval cache not being persisted in `nix develop` (since #10570)
- Don't attempt to commit cache transaction if there is no active transaction, which will spew errors in edge cases
- Drive-by: trivial typo fix
Progress on #5638
There are still a global fetcher and eval settings, but they are pushed
down into `libnixcmd`, which is a lot less bad a place for this sort of
thing.
Continuing process pioneered in
52bfccf8d8.
This improves the error message of nix-env -qa, among others, which
is crucial for understanding some ofborg eval error reports, such as
https://gist.github.com/GrahamcOfBorg/89101ca9c2c855d288178f1d3c78efef
After this change, it will report the same trace, but also start with
```
error:
… while evaluating the attribute 'devShellTools'
… while evaluating the attribute 'nixos'
… while evaluating the attribute 'docker-tools-nix-shell'
… while evaluating the attribute 'aarch64-darwin'
… from call site
at /home/user/h/nixpkgs/outpaths.nix:48:6:
47| tweak = lib.mapAttrs
48| (name: val:
| ^
49| if name == "recurseForDerivations" then true
<same>
```
move together all syntactic and semantic information into one
page, and add a page on data types, which in turn links to the syntax and
semantics.
also split out the note on scoping rules into its own page.
Co-authored-by: Ryan Hendrickson <ryan.hendrickson@alum.mit.edu>
