diff --git a/synapse/api/filtering.py b/synapse/api/filtering.py
index 3b3ef70750..27f8b99e3d 100644
--- a/synapse/api/filtering.py
+++ b/synapse/api/filtering.py
@@ -18,6 +18,7 @@ from synapse.types import UserID, RoomID
from twisted.internet import defer
import ujson as json
+import re
class Filtering(object):
@@ -71,6 +72,21 @@ class Filtering(object):
if key in user_filter_json["room"]:
self._check_definition(user_filter_json["room"][key])
+ if "event_fields" in user_filter_json:
+ if type(user_filter_json["event_fields"]) != list:
+ raise SynapseError(400, "event_fields must be a list of strings")
+ for field in user_filter_json["event_fields"]:
+ if not isinstance(field, basestring):
+ raise SynapseError(400, "Event field must be a string")
+ # Don't allow '\\' in event field filters. This makes matching
+ # events a lot easier as we can then use a negative lookbehind
+ # assertion to split '\.' If we allowed \\ then it would
+ # incorrectly split '\\.'
+ if r'\\' in field:
+ raise SynapseError(
+ 400, r'The escape character \ cannot itself be escaped'
+ )
+
def _check_definition_room_lists(self, definition):
"""Check that "rooms" and "not_rooms" are lists of room ids if they
are present
@@ -152,6 +168,11 @@ class FilterCollection(object):
self.include_leave = filter_json.get("room", {}).get(
"include_leave", False
)
+ self._event_fields = filter_json.get("event_fields", [])
+ # Negative lookbehind assertion for '\'
+ # (?<!stuff) matches if the current position in the string is not preceded
+ # by a match for 'stuff'.
+ self._split_field_regex = re.compile(r'(?<!\\)\.')
def __repr__(self):
return "<FilterCollection %s>" % (json.dumps(self._filter_json),)
@@ -186,6 +207,54 @@ class FilterCollection(object):
def filter_room_account_data(self, events):
return self._room_account_data.filter(self._room_filter.filter(events))
+ def filter_event_fields(self, event):
+ """Remove fields from an event in accordance with the 'event_fields' of a filter.
+
+ If there are no event fields specified then all fields are included.
+ The entries may include '.' charaters to indicate sub-fields.
+ So ['content.body'] will include the 'body' field of the 'content' object.
+ A literal '.' character in a field name may be escaped using a '\'.
+
+ Args:
+ event(dict): The raw event to filter
+ Returns:
+ dict: The same event with some fields missing, if required.
+ """
+ for field in self._event_fields:
+ self.filter_field(event, field)
+ return event
+
+ def filter_field(self, dictionary, field):
+ """Filter the given field from the given dictionary.
+
+ Args:
+ dictionary(dict): The dictionary to remove the field from.
+ field(str): The key to remove.
+ Returns:
+ dict: The same dictionary with the field removed.
+ """
+ # "content.body.thing\.with\.dots" => ["content", "body", "thing\.with\.dots"]
+ sub_fields = self._split_field_regex.split(field)
+ # remove escaping so we can use the right key names when deleting
+ sub_fields = [f.replace(r'\.', r'.') for f in sub_fields]
+
+ # common case e.g. 'origin_server_ts'
+ if len(sub_fields) == 1:
+ dictionary.pop(sub_fields[0], None)
+ # nested field e.g. 'content.body'
+ elif len(sub_fields) > 1:
+ # Pop the last field as that's the key to delete and we need the
+ # parent dict in order to remove the key. Drill down to the right dict.
+ key_to_delete = sub_fields.pop(-1)
+ sub_dict = dictionary
+ for sub_field in sub_fields:
+ if sub_field in sub_dict and type(sub_dict[sub_field]) == dict:
+ sub_dict = sub_dict[sub_field]
+ else:
+ return dictionary
+ sub_dict.pop(key_to_delete, None)
+ return dictionary
+
class Filter(object):
def __init__(self, filter_json):
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