Review compilation-related env vars in Spicy feature

[J-Gras]

For Spicy packages, the template manually resets some environment variables in btest.cfg:

package-template/__init__.py

Lines 195 to 214 in 17c8367

	# Manually merge Spicy analyzer-specific changes to `testing/btest.cfg`.
	with open(pkg_file("testing", "btest.cfg"), "ab") as btest_cfg:
	btest_cfg.write(
	bytes(
	textwrap.dedent(
	"""\
	DIST=%(testbase)s/..
	# Set compilation-related variables to well-defined state.
	CC=
	CXX=
	CFLAGS=
	CPPFLAGS=
	CXXFLAGS=
	LDFLAGS=
	DYLDFLAGS=
	"""
	),
	"ascii",
	)
	)

Would be nice to review whether it's worth to keep this and if so, if it makes sense to add this to plugins in general.

[bbannier]

The general idea with suppressing compiler- and linker-related env vars is that users might set these to undesirable values which could have an effect on tests compiling C++ files (e.g., tests of plugin installation picking them up). I do not recall a reason why they would be relevant for Spicy since we use namespaced variables like HILTI_CXX (the variables are documented in https://docs.zeek.org/projects/spicy/en/latest/toolchain.html). The only needed variable is DIST which is used in a generated test.

At the very least we should probably move these into the Plugin feature if we do not want to drop them completely.

[J-Gras]

I think there is another gotcha: It looks like the env vars are just appended to the file. I've a config that uses multiple alternatives. Hence, the new vars are only added to the last alternative.

[bbannier]

I think there is another gotcha: It looks like the env vars are just appended to the file. I've a config that uses multiple alternatives. Hence, the new vars are only added to the last alternative.

Is that a use case that comes up when combining features this template ships, or something downstream from here? The current "templating" mechanism here is not very smart (e.g., it does not really know the full contents of the file it modifies) but we took some care that certain features here combine compose reasonably, but this is likely impossible in general.

[J-Gras]

Is that a use case that comes up when combining features this template ships, or something downstream from here?

This came up when combining a custom feature that configures multiple alternatives in btest.cfg and the Spicy feature.