nix-super/doc/manual/rl-next/build-hook-default.md
John Ericson 58b03ef1cd Move NIX_BIN_DIR and all logic using it to the Nix executable itself
This is because with the split packages of the Meson build, we simply
have no idea what directory the binaries will be installed in when we
build the library.

In the process of doing so, consolidate and make more sophisticated the
logic to cope with a few corner cases (e.g. `NIX_BIN_DIR` exists, but no
binaries are inside it).

Co-authored-by: Robert Hensing <roberth@users.noreply.github.com>
2024-08-12 12:29:17 -04:00

2 KiB

synopsis prs
The `build-hook` setting's default is less useful when using `libnixstore` as a library
11178

This is an obscure issue that only affects usage of the libnixstore library outside of the Nix executable.

As part the ongoing rewrite of the build system to use Meson, we are also switching to packaging individual Nix components separately (and building them in separate derivations). This means that when building libnixstore we do not know where the Nix binaries will be installed --- libnixstore doesn't know about downstream consumers like the Nix binaries at all.

This is also unrelated to the post-build-hook, which is often used for pushing to a cache.*

This has a small adverse affect on remote building --- the build-remote executable that is specified from the build-hook setting will not be gotten from the (presumed) installation location, but instead looked up on the PATH. This means that other applications linking libnixstore that wish to use remote building must arrange for the nix command to be on the PATH (or manually overriding build-hook) in order for that to work.

Long term we don't envision this being a downside, because we plan to get rid of build-remote and the build hook setting entirely. There is simply no need to add a second layer of remote-procedure-calling when we want to connect to a remote builder. The build hook protocol did in principle support custom ways of remote building, but that can also be accomplished with a custom service for the ssh or daemon/ssh-ng protocols, or with a custom store type i.e. Store subclass.

The Perl bindings no longer expose getBinDir either, since they libraries those bindings wrap no longer know the location of installed binaries as described above.