# Testability guard
#
# Tree testability is a single top-level property tracked by
# $(TOPDIR)/dirs-all.done: created by a full `make all` from the topdir,
# removed by `make clean`. A per-dir `make test` only makes sense when the tree
# is importable, i.e. testable. So `test` requires testability, and a `make
# clean` that drops artifacts crucial for testing (a Python module's
# __init__.py, ...) invalidates it.

.PHONY: testability invalidate-testability

TEST_GUARD                   = $(TOPDIR)/dirs-all.done

all:

testability:
	@test -f "$(TEST_GUARD)" || \
		{ echo 'Error: Tree not testable -- run "make all" (or "make test") from project root to fix that!' >&2; exit 1; }

invalidate-testability:
	$(RM) -f "$(TEST_GUARD)"