Rather than having them plain strings scattered through the whole
codebase, create an enum containing all the known experimental features.
This means that
- Nix can now `warn` when an unkwown experimental feature is passed
(making it much nicer to spot typos and spot deprecated features)
- It’s now easy to remove a feature altogether (once the feature isn’t
experimental anymore or is dropped) by just removing the field for the
enum and letting the compiler point us to all the now invalid usages
of it.
I had started the trend of doing `std::visit` by value (because a type
error once mislead me into thinking that was the only form that
existed). While the optomizer in principle should be able to deal with
extra coppying or extra indirection once the lambdas inlined, sticking
with by reference is the conventional default. I hope this might even
improve performance.
This fixes
$ nix path-info -r $(type -P ls)
/nix/store/vfilzcp8a467w3p0mp54ybq6bdzb8w49-coreutils-8.32
/nix/store/5d821pjgzb90lw4zbg6xwxs7llm335wr-libunistring-0.9.10
...
/nix/store/mrv4y369nw6hg4pw8d9p9bfdxj9pjw0x-acl-2.3.0
/nix/store/vfilzcp8a467w3p0mp54ybq6bdzb8w49-coreutils-8.32
Also, output the paths in topologically sorted order like we used to.
In dry run mode, new derivations can't be create, so running the command on anything that has not been evaluated before results in an error message of the form `don't know how to build these paths (may be caused by read-only store access)`.
For comparison, the classical `nix-build --dry-run` doesn't use read-only mode.
Closes#1795
(cherry picked from commit 54525682df707742e58311c32e9c9cb18de1e31f)
If the store path contains a flake, this means that a command like
"nix path-info /path" will show info about /path, not about the
default output of the flake in /path. If you want the latter, you can
explicitly ask for it by doing "nix path-info path:/path".
Fixes#4568.
Use `$(libdir)` while installing .pc files looks like a more generic
solution. For example, it will work for distributions like RHEL or
Fedora where .pc files are installed in `/usr/lib64/pkgconfig`.
With this, we don't have to copy the entire .drv closure to the
destination store ahead of time (or at all). Instead, buildPaths()
reads .drv files from the eval store and copies inputSrcs to the
destination store if it needs to build a derivation.
Issue #5025.
In particular, this now works:
$ nix path-info --eval-store auto --store https://cache.nixos.org nixpkgs#hello
Previously this would fail as it would try to upload the hello .drv to
cache.nixos.org. Now the .drv is instantiated in the local store, and
then we check for the existence of the outputs in cache.nixos.org.
