Fix logging usage in hooks pytest_sessionstart/finish #3340

Author: Vincent Barbaresi

changelog/3340.bugfix.rst

@@ -0,0 +1 @@
+Fix logging messages not shown in hooks `pytest_sessionstart()` and `pytest_sessionfinish()`.

src/_pytest/logging.py

@@ -497,6 +497,29 @@ def pytest_runtest_logfinish(self):
         with self._runtest_for(None, "finish"):
             yield
 
+    @pytest.hookimpl(hookwrapper=True, tryfirst=True)
+    def pytest_sessionfinish(self):
+        with self.live_logs_context():
+            if self.log_cli_handler:
+                self.log_cli_handler.set_when("sessionfinish")
+            if self.log_file_handler is not None:
+                with catching_logs(self.log_file_handler, level=self.log_file_level):
+                    yield
+            else:
+                yield
+
+    @pytest.hookimpl(hookwrapper=True, tryfirst=True)
+    def pytest_sessionstart(self):
+        self._setup_cli_logging()
+        with self.live_logs_context():
+            if self.log_cli_handler:
+                self.log_cli_handler.set_when("sessionstart")
+            if self.log_file_handler is not None:
+                with catching_logs(self.log_file_handler, level=self.log_file_level):
+                    yield
+            else:
+                yield
+
     @pytest.hookimpl(hookwrapper=True)
     def pytest_runtestloop(self, session):
         """Runs all collected test items."""

testing/logging/test_reporting.py

@@ -966,3 +966,39 @@ def test_simple():
         assert "Normal message" in contents
         assert "debug message in test_simple" not in contents
         assert "info message in test_simple" in contents
+
+
+def test_log_in_hooks(testdir):
+    log_file = testdir.tmpdir.join("pytest.log").strpath
+
+    testdir.makeini(
+        """
+        [pytest]
+        log_file={}
+        log_file_level = INFO
+        log_cli=true
+        """.format(
+            log_file
+        )
+    )
+    testdir.makeconftest(
+        """
+        import logging
+
+        def pytest_runtestloop(session):
+            logging.info('runtestloop')
+
+        def pytest_sessionstart(session):
+            logging.info('sessionstart')
+
+        def pytest_sessionfinish(session, exitstatus):
+            logging.info('sessionfinish')
+    """
+    )
+    result = testdir.runpytest()
+    result.stdout.fnmatch_lines(["*sessionstart*", "*runtestloop*", "*sessionfinish*"])
+    with open(log_file) as rfh:
+        contents = rfh.read()
+        assert "sessionstart" in contents
+        assert "runtestloop" in contents
+        assert "sessionfinish" in contents