This returns the fingerprint for a specific subpath. This is intended
for "composite" accessors like MountedSourceAccessor, where different
subdirectories can have different fingerprints.
Previously, Nix would not create a cache entry for substituted/cached
inputs
This led to severe slowdowns in some scenarios where a large input (like
Nixpkgs) had already been unpacked to the store but didn't exist in a
users cache, as described in https://github.com/NixOS/nix/issues/11228
Using the same method as https://github.com/NixOS/nix/pull/12911, we can
create a cache entry for the fingerprint of substituted/cached inputs
and avoid this problem entirely
These counters are extremely expensive in a multi-threaded
program. For instance, disabling them speeds up evaluation of the
NixOS/nix/2.21.2 from 32.6s to 17.8s.
With this change, the store-wide `getFSAccessor` has only one usage left
--- the evaluator. If we get rid of that (as is planned), we can then
remove that method altogether, simplifying `Store`. Hurray!
I removed the store dir by mistake from the pretty-printed (for humans)
output in eb643d034f. That change was not
supposed to change output.
This is sometimes easier / more performant to implement, and
independently it is also a more convenient interface for many callers.
The existing store-wide `getFSAccessor` is only used for
- `nix why-depends`
- the evaluator
I hope we can get rid of it for those, too, and then we have the option
of getting rid of the store-wide method.
Co-authored-by: Sergei Zimmerman <sergei@zimmerman.foo>
Old code is now just used for `nix build` --- there is no CLI breaking
change.
Test the new format, too.
The new format is not currently used, but will be used going forward,
for example in the C API.
Progress on #13570
This brings them in line with the other tests, and furthers my goals of
separating unit test data from code.
Doing this cleanup as part of my #13570 effort, but strictly-speaking,
this is separate as these data types' JSON never contained and store
paths or store dirs, just simple output name strings.
Tested by building with b_sanitize=thread and running:
nix flake prefetch-inputs --store "dummy://?read-only=false"
It might make sense to move this utility class out of dummy-store.cc,
but it seems fine for now.
No behavior is changed, just:
- Declare a canonical `nlohmnan::json::adl_serializer`
- Use `json-utils.hh` to shorten code without getting worse error
messages.
Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
