Add a command-line option to enable audit, using Python 3.8 sys.addau…

…dithook()

That's a debugging feature.

Try '--audit os' or '--audit all'

picard/tagger.py

@@ -212,6 +212,60 @@ def __str__(self):
         return f"files: {repr(self.files)}  mbids: f{repr(self.mbids)}  urls: {repr(self.urls)}"
 
 
+def setup_audit(prefixes_string):
+    """Setup audit hook according to `audit` command-line option"""
+    if 'all' in prefixes_string.split(','):
+        def event_match(event):
+            return ('all', )
+    else:
+        # prebuild the dict, constant
+        PREFIXES_DICT = make_events_prefixes(prefixes_string)
+
+        def event_match(event):
+            return event_match_prefixes(event, PREFIXES_DICT)
+
+    def audit(event, args):
+        # we can't use log here, as it generates events
+        matched = event_match(event)
+        if matched:
+            matched = '.'.join(matched)
+            print(f'audit:{matched}: {event} args={args}')
+
+    sys.addaudithook(audit)
+
+
+def make_events_prefixes(prefixes_string):
+    """Build a dict with keys = length of prefix"""
+    from collections import defaultdict
+    d = defaultdict(list)
+    for p in set(tuple(e.split('.')) for e in prefixes_string.split(',')):
+        d[len(p)].append(p)
+    return d
+
+
+def prefixes_candidates_for_length(length, prefixes_dict):
+    """Generate prefixes that may match this length"""
+    for plen, v in prefixes_dict.items():
+        if length >= plen:
+            yield from v
+
+
+def event_match_prefixes(event, prefixes_dict):
+    """Matches event against prefixes
+       Typical case: we want to match `os.mkdir` if prefix is `os` or `os.mkdir`
+       but not the reverse: if prefix is `os.mkdir` we don't want to match an event named `os`
+       It returns False, or the matched prefix
+    """
+    ev = tuple(event.split('.'))
+    ev_len = len(ev)
+    # only use candidates that may have a chance to match
+    for p in prefixes_candidates_for_length(ev_len, prefixes_dict):
+        # check that all elements of ev are in p
+        if all(v == ev[i] for i, v in enumerate(p)):
+            return p
+    return False
+
+
 class Tagger(QtWidgets.QApplication):
 
     tagger_stats_changed = QtCore.pyqtSignal()
@@ -256,6 +310,10 @@ def __init__(self, picard_args, localedir, autoupdate, pipe_handler=None):
         if picard_args.debug or "PICARD_DEBUG" in os.environ:
             self.set_log_level(logging.DEBUG)
 
+        if sys.version_info[:3] > (3, 8):
+            if picard_args.audit:
+                setup_audit(picard_args.audit)
+
         # Main thread pool used for most background tasks
         self.thread_pool = QtCore.QThreadPool(self)
         # Two threads are needed for the pipe handler and command processing.
@@ -1437,6 +1495,11 @@ def process_picard_args():
     parser.add_argument("-display", nargs=1, help=argparse.SUPPRESS)
 
     # Picard specific arguments
+    if sys.version_info[:3] > (3, 8):
+        parser.add_argument("-a", "--audit", action='store',
+                            default=None,
+                            help="audit events passed as a comma-separated list, prefixes supported, "
+                            "use all to match any (see https://docs.python.org/3/library/audit_events.html#audit-events)")
     parser.add_argument("-c", "--config-file", action='store',
                         default=None,
                         help="location of the configuration file")