macOS arm64 `pg_client` 0.19.0 expects libpq from the standalone Homebrew formula

[prrao87]

Summary

Seems like a packaging compatibility issue, and could use a UX enhancement to not trip up new users working with homebrew on macOS.

The official macOS arm64 build of libpg_client.lbug_extension 0.19.0
references this absolute libpq path:

/opt/homebrew/opt/libpq/lib/libpq.5.dylib

That file is provided by Homebrew's standalone libpq formula. It is not
present on a machine that has PostgreSQL 18 installed only through the
postgresql@18 brew formula.

The same library is available at a different path on that installation:

/opt/homebrew/lib/postgresql@18/libpq.5.dylib

Because the extension records the first path in its install name, Ladybug
cannot load it on this setup. Relinking a copy of the extension to the second
path fixes the problem.

Environment

• PostgreSQL 18.4 installed with Homebrew postgresql@18
• macOS arm64
• pg_client extension binary 0.19.0 from the official release
• liblbug 0.19.1
• Standalone Homebrew libpq formula not installed

Reproduction

Install PostgreSQL with brew install postgresql@18, without installing the
separate libpq formula. Then inspect the extension and the two possible
library paths:

otool -L libpg_client.lbug_extension | grep libpq
# 	/opt/homebrew/opt/libpq/lib/libpq.5.dylib (compatibility version 5.0.0, ...)

ls /opt/homebrew/opt/libpq/lib/libpq.5.dylib
# ls: no such file or directory

ls /opt/homebrew/lib/postgresql@18/libpq.5.dylib
# /opt/homebrew/lib/postgresql@18/libpq.5.dylib

Loading the extension then fails:

LOAD EXTENSION '/path/to/libpg_client.lbug_extension';

Workaround

Relink a disposable copy of the extension to the libpq installed by
postgresql@18:

install_name_tool -change \
  /opt/homebrew/opt/libpq/lib/libpq.5.dylib \
  /opt/homebrew/lib/postgresql@18/libpq.5.dylib \
  libpg_client.lbug_extension

The patched copy loads successfully.

Possible fixes

• Use @rpath or a loader-relative install name and include the common
  Homebrew locations in LC_RPATH.
• Bundle or statically link libpq if its licensing and distribution terms
  allow that.
• Publish separate binaries for the supported Homebrew layouts, or relink the
  extension during installation.