Enable showing DeprecationWarning in debug_on and add unit test

satpy/tests/test_utils.py

@@ -17,9 +17,14 @@
 # satpy.  If not, see <http://www.gnu.org/licenses/>.
 """Testing of utils."""
 
+import logging
 import unittest
+import warnings
 from unittest import mock
+
+import pytest
 from numpy import sqrt
+
 from satpy.utils import angle2xyz, lonlat2xyz, xyz2angle, xyz2lonlat, proj_units_to_meters, get_satpos
 
 
@@ -307,3 +312,48 @@ def test_specific_check_satpy(self):
                     checked_fake = True
             self.assertTrue(checked_fake, "Did not find __fake module "
                                           "mentioned in checks")
+
+
+def test_debug_on(caplog):
+    """Test that debug_on is working as expected."""
+    from satpy.utils import debug_on, debug_off, debug
+
+    def depwarn():
+        logger = logging.getLogger("satpy.silly")
+        logger.debug("But now it's just got SILLY.")
+        warnings.warn("Stop that! It's SILLY.", DeprecationWarning)
+    warnings.filterwarnings("ignore", category=DeprecationWarning)
+    debug_on(False)
+    filts_before = warnings.filters.copy()
+    # test that logging on, but deprecation warnings still off
+    with caplog.at_level(logging.DEBUG):
+        depwarn()
+    assert warnings.filters == filts_before
+    assert "But now it's just got SILLY." in caplog.text
+    debug_on(True)
+    # test that logging on and deprecation warnings on
+    with pytest.warns(DeprecationWarning):
+        depwarn()
+    assert warnings.filters != filts_before
+    debug_off()  # other tests assume debugging is off
+    # test that filters were reset
+    assert warnings.filters == filts_before
+    with debug():
+        assert warnings.filters != filts_before
+    assert warnings.filters == filts_before
+
+
+def test_logging_on_and_off(caplog):
+    """Test that switching logging on and off works."""
+    from satpy.utils import logging_on, logging_off
+    logger = logging.getLogger("satpy.silly")
+    logging_on()
+    with caplog.at_level(logging.WARNING):
+        logger.debug("I'd like to leave the army please, sir.")
+        logger.warning("Stop that!  It's SILLY.")
+    assert "Stop that!  It's SILLY" in caplog.text
+    assert "I'd like to leave the army please, sir." not in caplog.text
+    logging_off()
+    with caplog.at_level(logging.DEBUG):
+        logger.warning("You've got a nice army base here, Colonel.")
+    assert "You've got a nice army base here, Colonel." not in caplog.text

satpy/utils.py

@@ -21,6 +21,7 @@
 import logging
 import os
 import warnings
+import contextlib
 from typing import Mapping
 
 import numpy as np
@@ -43,16 +44,83 @@ def ensure_dir(filename):
         os.makedirs(directory)
 
 
-def debug_on():
-    """Turn debugging logging on."""
+def debug_on(deprecation_warnings=True):
+    """Turn debugging logging on.
+
+    Sets up a StreamHandler to to `sys.stderr` at debug level for all
+    loggers, such that all debug messages (and log messages with higher
+    severity) are logged to the standard error stream.
+
+    By default, since Satpy 0.26, this also enables the global visibility
+    of deprecation warnings.  This can be suppressed by passing a false
+    value.
+
+    Args:
+        deprecation_warnings (Optional[bool]): Switch on deprecation warnings.
+            Defaults to True.
+
+    Returns:
+        None
+    """
     logging_on(logging.DEBUG)
+    if deprecation_warnings:
+        deprecation_warnings_on()
+
+
+def debug_off():
+    """Turn debugging logging off.
+
+    This disables both debugging logging and the global visibility of
+    deprecation warnings.
+    """
+    logging_off()
+    deprecation_warnings_off()
+
+
+@contextlib.contextmanager
+def debug(deprecation_warnings=True):
+    """Context manager to temporarily set debugging on.
+
+    Example::
+
+        >>> with satpy.utils.debug():
+        ...     code_here()
+
+    Args:
+        deprecation_warnings (Optional[bool]): Switch on deprecation warnings.
+            Defaults to True.
+    """
+    debug_on(deprecation_warnings=deprecation_warnings)
+    yield
+    debug_off()
 
 
 def trace_on():
     """Turn trace logging on."""
     logging_on(TRACE_LEVEL)
 
 
+class _WarningManager:
+    """Class to handle switching warnings on and off."""
+
+    filt = None
+
+
+_warning_manager = _WarningManager()
+
+
+def deprecation_warnings_on():
+    """Switch on deprecation warnings."""
+    warnings.filterwarnings("default", category=DeprecationWarning)
+    _warning_manager.filt = warnings.filters[0]
+
+
+def deprecation_warnings_off():
+    """Switch off deprecation warnings."""
+    if _warning_manager.filt in warnings.filters:
+        warnings.filters.remove(_warning_manager.filt)
+
+
 def logging_on(level=logging.WARNING):
     """Turn logging on."""
     global _is_logging_on