py-test.mk: Generate conftest.py

Generate a standard conftest.py, mostly for customizing pytest's bombastic test header, which otherwise lets the more informative make output look too pale in comparison.
Signed-off-by: Jan Lindemann <jan@janware.com>

make/py-test.mk

@@ -1,6 +1,23 @@
-PYTHON_RUNNER               ?= pytest -v
+PY_CONFTEST                 ?= conftest.py
+PY_UPDATE_PY_CONFTEST       ?= true
+ifeq ($(PY_UPDATE_PY_CONFTEST),true)
+  PY_GENERATED              += $(PY_CONFTEST)
+endif
+
+PY_CONFTEST_CMD             ?= /bin/bash $(JWB_SCRIPT_DIR)/python-tools.sh create-conftest-py
+PY_TEST_ARGS                ?= -v
+PYTHON_RUNNER               := pytest $(PY_TEST_ARGS)
 
 include $(JWBDIR)/make/py-run.mk
 
 all:
 test: run
+run: $(PY_GENERATED)
+
+$(PY_CONFTEST):
+	$(PY_CONFTEST_CMD) > $@.tmp
+	mv $@.tmp $@
+
+clean: clean.generated
+clean.generated:
+	rm -f $(PY_GENERATED)

scripts/python-tools.sh

@@ -32,6 +32,39 @@ module_path()
 	fi
 }
 
+cmd_create_conftest_py()
+{
+	cat <<-'EOT'
+	import os
+	import sys
+	import shutil
+
+	def pytest_configure(config):
+	    import _pytest.terminal
+	    import _pytest.timing as timing
+
+	    # orig = _pytest.terminal.TerminalReporter.pytest_sessionstart
+
+	    def patched(self, session):
+	        width = shutil.get_terminal_size().columns
+	        d = os.path.basename(os.getcwd())
+	        text = f"Running pytest for {d}"
+	        # Center text within terminal width, matching pytest footer style
+	        padding = width - len(text) - 2
+	        if padding > 0:
+	            left = padding // 2
+	            right = padding - left
+	            banner = "=" * left + f" {text} " + "=" * right
+	        else:
+	            banner = text
+	        print(banner, file = sys.stderr)
+	        self._session = session
+	        self._session_start = timing.Instant()
+
+	    _pytest.terminal.TerminalReporter.pytest_sessionstart = patched
+EOT
+}
+
 cmd_create_init()
 {
 	__add_seen() {