diff --git a/synapse/events/utils.py b/synapse/events/utils.py
index 0e9fd902af..4febd98f43 100644
--- a/synapse/events/utils.py
+++ b/synapse/events/utils.py
@@ -16,6 +16,15 @@
from synapse.api.constants import EventTypes
from . import EventBase
+import re
+
+# Split strings on "." but not "\." This uses a negative lookbehind assertion for '\'
+# (?<!stuff) matches if the current position in the string is not preceded
+# by a match for 'stuff'.
+# TODO: This is fast, but fails to handle "foo\\.bar" which should be treated as
+# the literal fields "foo\" and "bar" but will instead be treated as "foo\\.bar"
+SPLIT_FIELD_REGEX = re.compile(r'(?<!\\)\.')
+
def prune_event(event):
""" Returns a pruned version of the given event, which removes all keys we
@@ -97,6 +106,87 @@ def prune_event(event):
)
+def _copy_field(src, dst, field):
+ """Copy the field in 'src' to 'dst'.
+
+ For example, if src={"foo":{"bar":5}} and dst={}, and field=["foo","bar"]
+ then dst={"foo":{"bar":5}}.
+
+ Args:
+ src(dict): The dict to read from.
+ dst(dict): The dict to modify.
+ field(list<str>): List of keys to drill down to in 'src'.
+ """
+ if len(field) == 0: # this should be impossible
+ return
+ if len(field) == 1: # common case e.g. 'origin_server_ts'
+ if field[0] in src:
+ dst[field[0]] = src[field[0]]
+ return
+
+ # Else is a nested field e.g. 'content.body'
+ # Pop the last field as that's the key to move across and we need the
+ # parent dict in order to access the data. Drill down to the right dict.
+ key_to_move = field.pop(-1)
+ sub_dict = src
+ for sub_field in field: # e.g. sub_field => "content"
+ if sub_field in sub_dict and type(sub_dict[sub_field]) == dict:
+ sub_dict = sub_dict[sub_field]
+ else:
+ return
+
+ if key_to_move not in sub_dict:
+ return
+
+ # Insert the key into the output dictionary, creating nested objects
+ # as required. We couldn't do this any earlier or else we'd need to delete
+ # the empty objects if the key didn't exist.
+ sub_out_dict = dst
+ for sub_field in field:
+ if sub_field not in sub_out_dict:
+ sub_out_dict[sub_field] = {}
+ sub_out_dict = sub_out_dict[sub_field]
+ sub_out_dict[key_to_move] = sub_dict[key_to_move]
+
+
+def only_fields(dictionary, fields):
+ """Return a new dict with only the fields in 'dictionary' which are present
+ in 'fields'.
+
+ 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:
+ dictionary(dict): The dictionary to read from.
+ fields(list<str>): A list of fields to copy over. Only shallow refs are
+ taken.
+ Returns:
+ dict: A new dictionary with only the given fields. If fields was empty,
+ the same dictionary is returned.
+ """
+ if len(fields) == 0:
+ return dictionary
+
+ # for each field, convert it:
+ # ["content.body.thing\.with\.dots"] => [["content", "body", "thing\.with\.dots"]]
+ split_fields = [SPLIT_FIELD_REGEX.split(f) for f in fields]
+
+ # for each element of the output array of arrays:
+ # remove escaping so we can use the right key names. This purposefully avoids
+ # using list comprehensions to avoid needless allocations as this may be called
+ # on a lot of events.
+ for field_array in split_fields:
+ for i, field in enumerate(field_array):
+ field_array[i] = field.replace(r'\.', r'.')
+
+ output = {}
+ for field_array in split_fields:
+ _copy_field(dictionary, output, field_array)
+ return output
+
+
def format_event_raw(d):
return d
@@ -137,7 +227,7 @@ def format_event_for_client_v2_without_room_id(d):
def serialize_event(e, time_now_ms, as_client_event=True,
event_format=format_event_for_client_v1,
- token_id=None):
+ token_id=None, event_fields=None):
# FIXME(erikj): To handle the case of presence events and the like
if not isinstance(e, EventBase):
return e
@@ -164,6 +254,9 @@ def serialize_event(e, time_now_ms, as_client_event=True,
d["unsigned"]["transaction_id"] = txn_id
if as_client_event:
- return event_format(d)
- else:
- return d
+ d = event_format(d)
+
+ if isinstance(event_fields, list):
+ d = only_fields(d, event_fields)
+
+ return d
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