Python part of the warnings subsystem.

Author: gvanrossum

Lib/warnings.py

@@ -0,0 +1,227 @@
+"""Python part of the warnings subsystem."""
+
+import sys, re, types
+
+defaultaction = "default"
+filters = []
+onceregistry = {}
+
+def warn(message, category=None, stacklevel=1):
+    """Issue a warning, or maybe ignore it or raise an exception."""
+    # Check category argument
+    if category is None:
+        category = UserWarning
+    assert issubclass(category, Warning)
+    # Get context information
+    try:
+        caller = sys._getframe(stacklevel)
+    except ValueError:
+        globals = sys.__dict__
+        lineno = 1
+    else:
+        globals = caller.f_globals
+        lineno = caller.f_lineno
+    module = globals['__name__']
+    filename = globals.get('__file__')
+    if filename:
+        fnl = filename.lower()
+        if fnl.endswith(".pyc") or fnl.endswith(".pyo"):
+            filename = filename[:-1]
+    else:
+        if module == "__main__":
+            filename = sys.argv[0]
+        if not filename:
+            filename = module
+    # Quick test for common case
+    registry = globals.setdefault("__warningregistry__", {})
+    key = (message, category, lineno)
+    if registry.get(key):
+        return
+    # Search the filters
+    for item in filters:
+        action, msg, cat, mod, ln = item
+        if (msg.match(message) and
+            issubclass(category, cat) and
+            mod.match(module) and
+            (ln == 0 or lineno == ln)):
+            break
+    else:
+        action = defaultaction
+    # Early exit actions
+    if action == "ignore":
+        registry[key] = 1
+        return
+    if action == "error":
+        raise category(message)
+    # Other actions
+    if action == "once":
+        registry[key] = 1
+        oncekey = (message, category)
+        if onceregistry.get(oncekey):
+            return
+        onceregistry[oncekey] = 1
+    elif action == "always":
+        pass
+    elif action == "module":
+        registry[key] = 1
+        altkey = (message, category, 0)
+        if registry.get(altkey):
+            return
+        registry[altkey] = 1
+    elif action == "default":
+        registry[key] = 1
+    else:
+        # Unrecognized actions are errors
+        raise RuntimeError(
+              "Unrecognized action (%s) in warnings.filters:\n %s" %
+              (`action`, str(item)))
+    # Print message and context
+    showwarning(message, category, filename, lineno)
+
+def showwarning(message, category, filename, lineno, file=None):
+    """Hook to write a warning to a file; replace if you like."""
+    if file is None:
+        file = sys.stderr
+    file.write(formatwarning(message, category, filename, lineno))
+
+def formatwarning(message, category, filename, lineno):
+    """Hook to format a warning the standard way."""
+    import linecache
+    s =  "%s:%s: %s: %s\n" % (filename, lineno, category.__name__, message)
+    line = linecache.getline(filename, lineno).strip()
+    if line:
+        s = s + "  " + line + "\n"
+    return s
+
+def filterwarnings(action, message="", category=Warning, module="", lineno=0):
+    """Insert an entry into the list of warnings filters (at the front).
+
+    Use assertions to check that all arguments have the right type."""
+    assert action in ("error", "ignore", "always", "default", "module",
+                      "once"), "invalid action: %s" % `action`
+    assert isinstance(message, types.StringType), "message must be a string"
+    assert isinstance(category, types.ClassType), "category must be a class"
+    assert issubclass(category, Warning), "category must be a Warning subclass"
+    assert type(module) is types.StringType, "module must be a string"
+    assert type(lineno) is types.IntType and lineno >= 0, \
+           "lineno must be an int >= 0"
+    filters.insert(0, (action, re.compile(message, re.I), category,
+                       re.compile(module), lineno))
+
+def resetwarnings():
+    """Reset the list of warnings filters to its default state."""
+    filters[:] = []
+
+class _OptionError(Exception):
+    """Exception used by option processing helpers."""
+    pass
+
+# Helper to process -W options passed via sys.warnoptions
+def _processoptions(args):
+    for arg in args:
+        try:
+            _setoption(arg)
+        except _OptionError, msg:
+            print >>sys.stderr, "Invalid -W option ignored:", msg
+
+# Helper for _processoptions()
+def _setoption(arg):
+        parts = arg.split(':')
+        if len(parts) > 5:
+            raise _OptionError("unparsable -W option %s" % `arg`)
+        while len(parts) < 5:
+            parts.append('')
+        action, message, category, module, lineno = [s.strip()
+                                                     for s in parts]
+        action = _getaction(action)
+        message = re.escape(message)
+        category = _getcategory(category)
+        module = re.escape(module)
+        if module:
+            module = module + '$'
+        if lineno:
+            try:
+                lineno = int(lineno)
+                if lineno < 0:
+                    raise ValueError
+            except (ValueError, OverflowError):
+                raise _OptionError("invalid lineno %s" % `lineno`)
+        else:
+            lineno = 0
+        filterwarnings(action, message, category, module, lineno)
+
+# Helper for _setoption()
+def _getaction(action):
+    if not action:
+        return "default"
+    if action == "all": return "always" # Alias
+    for a in ['default', 'always', 'ignore', 'module', 'once', 'error']:
+        if a.startswith(action):
+            return a
+    raise _OptionError("invalid action: %s" % `action`)
+
+# Helper for _setoption()
+def _getcategory(category):
+    if not category:
+        return Warning
+    if re.match("^[a-zA-Z0-9_]+$", category):
+        try:
+            cat = eval(category)
+        except KeyError:
+            raise _OptionError("invalid warning category: %s" % `category`)
+    else:
+        i = category.rfind(".")
+        module = category[:i]
+        klass = category[i+1:]
+        m = __import__(module, None, None, [klass])
+        cat = getattr(m, klass)
+    if (not isinstance(cat, types.ClassType) or
+        not issubclass(cat, Warning)):
+        raise _OptionError("invalid warning category: %s" % `category`)
+    return cat
+
+# Self-test
+def _test():
+    import getopt
+    testoptions = []
+    try:
+        opts, args = getopt.getopt(sys.argv[1:], "W:")
+    except getopt.error, msg:
+        print >>sys.stderr, msg
+        return
+    for o, a in opts:
+        testoptions.append(a)
+    try:
+        _processoptions(testoptions)
+    except _OptionError, msg:
+        print >>sys.stderr, msg
+        return
+    for item in filters: print item
+    hello = "hello world"
+    warn(hello); warn(hello); warn(hello); warn(hello)
+    warn(hello, UserWarning)
+    warn(hello, DeprecationWarning)
+    for i in range(3):
+        warn(hello)
+    filterwarnings("error", "", Warning, "", 0)
+    try:
+        warn(hello)
+    except Exception, msg:
+        print "Caught", msg.__class__.__name__ + ":", msg
+    else:
+        print "No exception"
+    resetwarnings()
+    try:
+        filterwarnings("booh", "", Warning, "", 0)
+    except Exception, msg:
+        print "Caught", msg.__class__.__name__ + ":", msg
+    else:
+        print "No exception"
+
+# Module initialization
+if __name__ == "__main__":
+    import __main__
+    sys.modules['warnings'] = __main__
+    _test()
+else:
+    _processoptions(sys.warnoptions)