LoggingPlugin: Expose setting log_file_handler

- This patch allows to set log_file (path) from hook

Signed-off-by: Thomas Hisch
Signed-off-by: Andras Mitzki <andras.mitzki@balabit.com>

AUTHORS

@@ -16,6 +16,7 @@ Allan Feldman
 Aly Sivji
 Anatoly Bubenkoff
 Anders Hovmöller
+Andras Mitzki
 Andras Tim
 Andrea Cimatoribus
 Andreas Zeidler

changelog/4707.feature.rst

@@ -0,0 +1 @@
+With the help of new ``set_log_path()`` method there is a way to set ``log_file`` paths from hooks.

doc/en/logging.rst

@@ -198,6 +198,9 @@ option names are:
 * ``log_file_format``
 * ``log_file_date_format``
 
+You can call ``set_log_path()`` to customize the log_file path dynamically. This functionality
+is considered **experimental**.
+
 .. _log_release_notes:
 
 Release notes

src/_pytest/logging.py

@@ -13,6 +13,7 @@ import six
 import pytest
 from _pytest.compat import dummy_context_manager
 from _pytest.config import create_terminal_writer
+from _pytest.pathlib import Path
 
 
 DEFAULT_LOG_FORMAT = "%(filename)-25s %(lineno)4d %(levelname)-8s %(message)s"
@@ -399,22 +400,21 @@ class LoggingPlugin(object):
         )
         self.log_level = get_actual_log_level(config, "log_level")
 
-        log_file = get_option_ini(config, "log_file")
-        if log_file:
         self.log_file_level = get_actual_log_level(config, "log_file_level")
-
-            log_file_format = get_option_ini(config, "log_file_format", "log_format")
-            log_file_date_format = get_option_ini(
+        self.log_file_format = get_option_ini(config, "log_file_format", "log_format")
+        self.log_file_date_format = get_option_ini(
             config, "log_file_date_format", "log_date_format"
         )
-            # Each pytest runtests session will write to a clean logfile
+        self.log_file_formatter = logging.Formatter(
+            self.log_file_format, datefmt=self.log_file_date_format
+        )
+
+        log_file = get_option_ini(config, "log_file")
+        if log_file:
             self.log_file_handler = logging.FileHandler(
                 log_file, mode="w", encoding="UTF-8"
             )
-            log_file_formatter = logging.Formatter(
-                log_file_format, datefmt=log_file_date_format
-            )
-            self.log_file_handler.setFormatter(log_file_formatter)
+            self.log_file_handler.setFormatter(self.log_file_formatter)
         else:
             self.log_file_handler = None
 
@@ -468,6 +468,27 @@ class LoggingPlugin(object):
             log_cli_handler, formatter=log_cli_formatter, level=log_cli_level
         )
 
+    def set_log_path(self, fname):
+        """Public method, which can set filename parameter for
+        Logging.FileHandler(). Also creates parent directory if
+        it does not exist.
+
+        .. warning::
+            Please considered as an experimental API.
+        """
+        fname = Path(fname)
+
+        if not fname.is_absolute():
+            fname = Path(self._config.rootdir, fname)
+
+        if not fname.parent.exists():
+            fname.parent.mkdir(exist_ok=True, parents=True)
+
+        self.log_file_handler = logging.FileHandler(
+            str(fname), mode="w", encoding="UTF-8"
+        )
+        self.log_file_handler.setFormatter(self.log_file_formatter)
+
     def _log_cli_enabled(self):
         """Return True if log_cli should be considered enabled, either explicitly
         or because --log-cli-level was given in the command-line.
@@ -490,6 +511,15 @@ class LoggingPlugin(object):
 
     @contextmanager
     def _runtest_for(self, item, when):
+        with self._runtest_for_main(item, when):
+            if self.log_file_handler is not None:
+                with catching_logs(self.log_file_handler, level=self.log_file_level):
+                    yield
+            else:
+                yield
+
+    @contextmanager
+    def _runtest_for_main(self, item, when):
         """Implements the internals of pytest_runtest_xxx() hook."""
         with catching_logs(
             LogCaptureHandler(), formatter=self.formatter, level=self.log_level

testing/logging/test_reporting.py

@@ -1002,3 +1002,51 @@ def test_log_in_hooks(testdir):
         assert "sessionstart" in contents
         assert "runtestloop" in contents
         assert "sessionfinish" in contents
+
+
+def test_log_set_path(testdir):
+    report_dir_base = testdir.tmpdir.strpath
+
+    testdir.makeini(
+        """
+        [pytest]
+        log_file_level = DEBUG
+        log_cli=true
+        """
+    )
+    testdir.makeconftest(
+        """
+            import os
+            import pytest
+            @pytest.hookimpl(hookwrapper=True, tryfirst=True)
+            def pytest_runtest_setup(item):
+                config = item.config
+                logging_plugin = config.pluginmanager.get_plugin("logging-plugin")
+                report_file = os.path.join({}, item._request.node.name)
+                logging_plugin.set_log_path(report_file)
+                yield
+        """.format(
+            repr(report_dir_base)
+        )
+    )
+    testdir.makepyfile(
+        """
+            import logging
+            logger = logging.getLogger("testcase-logger")
+            def test_first():
+                logger.info("message from test 1")
+                assert True
+
+            def test_second():
+                logger.debug("message from test 2")
+                assert True
+        """
+    )
+    testdir.runpytest()
+    with open(os.path.join(report_dir_base, "test_first"), "r") as rfh:
+        content = rfh.read()
+        assert "message from test 1" in content
+
+    with open(os.path.join(report_dir_base, "test_second"), "r") as rfh:
+        content = rfh.read()
+        assert "message from test 2" in content