jupyterlab/jupyterlab/debuglog.py

# coding: utf-8
"""A mixin for adding a debug log file.

"""

# Copyright (c) Jupyter Development Team.
# Distributed under the terms of the Modified BSD License.

import contextlib
import logging
import os
import sys
import tempfile
import traceback

from traitlets import Unicode, default
from traitlets.config import Configurable

class DebugLogFileMixin(Configurable):
    debug_log_path = Unicode('', config=True, help='Path to use for the debug log file')

    @contextlib.contextmanager
    def debug_logging(self):
        log_path = self.debug_log_path
        if os.path.isdir(log_path):
            log_path = os.path.join(log_path, 'jupyterlab-debug.log')
        if not log_path:
            handle, log_path = tempfile.mkstemp(prefix='jupyterlab-debug-', suffix='.log')
            os.close(handle)
        log = self.log

        # Transfer current log level to the handlers:
        for h in log.handlers:
            h.setLevel(self.log_level)
        log.setLevel('DEBUG')

        # Create our debug-level file handler:
        _debug_handler = logging.FileHandler(
            log_path, 'w', 'utf8', delay=True)
        _log_formatter = self._log_formatter_cls(fmt=self.log_format, datefmt=self.log_datefmt)
        _debug_handler.setFormatter(_log_formatter)
        _debug_handler.setLevel('DEBUG')

        log.addHandler(_debug_handler)

        try:
            yield
        except Exception as ex:
            _, _, exc_traceback = sys.exc_info()
            msg = traceback.format_exception(ex.__class__, ex, exc_traceback)
            for line in msg:
                self.log.debug(line)
            if isinstance(ex, SystemExit):
                print('An error occured. See the log file for details: ', log_path)
                raise
            print('An error occured.')
            print(msg[-1].strip())
            print('See the log file for details: ', log_path)
            self.exit(1)
        else:
            log.removeHandler(_debug_handler)
            _debug_handler.flush()
            _debug_handler.close()
            try:
                os.remove(log_path)
            except FileNotFoundError:
                pass
        log.removeHandler(_debug_handler)