pip install overrides existing build configuration

[Alvaro-Kothe]

When using meson-python with editable installs, running pip install -e a second time, reusing the build directory, but without repeating the buildtype argument overwrites the existing build configuration.

Reproduction

#!/usr/bin/env bash

mkdir repro

# Create files for meson-python

cat <<EOF > repro/pyproject.toml
[project]
name = "foo"
version = "0.0.1"

[build-system]
build-backend = "mesonpy"
requires = ["meson-python"]
EOF

cat <<EOF > repro/meson.build
project('foo', 'c', version: '0.1.0')
EOF

python -m pip install meson-python

# Create a debug build
pip install --no-build-isolation -e repro -Csetup-args=-Dbuildtype=debug -Cbuild-dir=debug

grep buildtype repro/debug/meson-logs/meson-setup.txt
# buildtype   : debug

# If I decide to reuse this build directory,
# and I call `pip install` without `-Csetup-args=-Dbuildtype=debug`
# it reconfigures to have `buildtype=release` instead of reusing the current configuration.
pip install --no-build-isolation -e repro -Cbuild-dir=debug

grep buildtype repro/debug/meson-logs/meson-setup.txt
# buildtype   : release

[rgommers]

This is by design; you never have to re-run the editable install command to keep working on code (including compiled code), so if you do and you're changing the build options, you are asking for a new build configuration.

Do you see a problem with that?

This is where the reconfigure happens:

meson-python/mesonpy/__init__.py

Lines 814 to 819 in 4977b7d

	# reconfigure if we have a valid Meson build directory. Meson
	# uses the presence of the 'meson-private/coredata.dat' file
	# in the build directory as indication that the build
	# directory has already been configured and arranges this file
	# to be created as late as possible or deleted if something
	# goes wrong during setup.