1 files changed, 46 insertions, 0 deletions
diff --git a/src/flake8/plugins/notifier.py b/src/flake8/plugins/notifier.py
new file mode 100644
index 0000000..dc255c4
--- /dev/null
+++ b/src/flake8/plugins/notifier.py
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+"""Implementation of the class that registers and notifies listeners."""
+from flake8.plugins import _trie
+
+
+class Notifier(object):
+    """Object that tracks and notifies listener objects."""
+
+    def __init__(self):
+        """Initialize an empty notifier object."""
+        self.listeners = _trie.Trie()
+
+    def listeners_for(self, error_code):
+        """Retrieve listeners for an error_code.
+
+        There may be listeners registered for E1, E100, E101, E110, E112, and
+        E126. To get all the listeners for one of E100, E101, E110, E112, or
+        E126 you would also need to incorporate the listeners for E1 (since
+        they're all in the same class).
+
+        Example usage:
+
+        .. code-block:: python
+
+            from flake8 import notifier
+
+            n = notifier.Notifier()
+            # register listeners
+            for listener in n.listeners_for('W102'):
+                listener.notify(...)
+        """
+        path = error_code
+        while path:
+            node = self.listeners.find(path)
+            listeners = getattr(node, 'data', [])
+            for listener in listeners:
+                yield listener
+            path = path[:-1]
+
+    def notify(self, error_code, *args, **kwargs):
+        """Notify all listeners for the specified error code."""
+        for listener in self.listeners_for(error_code):
+            listener.notify(error_code, *args, **kwargs)
+
+    def register_listener(self, error_code, listener):
+        """Register a listener for a specific error_code."""
+        self.listeners.add(error_code, listener)