diff options
Diffstat (limited to 'synapse/events/utils.py')
| -rw-r--r-- | synapse/events/utils.py | 72 |
1 files changed, 58 insertions, 14 deletions
diff --git a/synapse/events/utils.py b/synapse/events/utils.py index e6d040176b..e7b7b78b84 100644 --- a/synapse/events/utils.py +++ b/synapse/events/utils.py @@ -22,6 +22,7 @@ from typing import ( Iterable, List, Mapping, + Match, MutableMapping, Optional, Union, @@ -46,12 +47,10 @@ if TYPE_CHECKING: from synapse.handlers.relations import BundledAggregations -# 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"(?<!\\)\.") +# Split strings on "." but not "\." (or "\\\."). +SPLIT_FIELD_REGEX = re.compile(r"\\*\.") +# Find escaped characters, e.g. those with a \ in front of them. +ESCAPE_SEQUENCE_PATTERN = re.compile(r"\\(.)") CANONICALJSON_MAX_INT = (2**53) - 1 CANONICALJSON_MIN_INT = -CANONICALJSON_MAX_INT @@ -253,6 +252,57 @@ def _copy_field(src: JsonDict, dst: JsonDict, field: List[str]) -> None: sub_out_dict[key_to_move] = sub_dict[key_to_move] +def _escape_slash(m: Match[str]) -> str: + """ + Replacement function; replace a backslash-backslash or backslash-dot with the + second character. Leaves any other string alone. + """ + if m.group(1) in ("\\", "."): + return m.group(1) + return m.group(0) + + +def _split_field(field: str) -> List[str]: + """ + Splits strings on unescaped dots and removes escaping. + + Args: + field: A string representing a path to a field. + + Returns: + A list of nested fields to traverse. + """ + + # Convert the field and remove escaping: + # + # 1. "content.body.thing\.with\.dots" + # 2. ["content", "body", "thing\.with\.dots"] + # 3. ["content", "body", "thing.with.dots"] + + # Find all dots (and their preceding backslashes). If the dot is unescaped + # then emit a new field part. + result = [] + prev_start = 0 + for match in SPLIT_FIELD_REGEX.finditer(field): + # If the match is an *even* number of characters than the dot was escaped. + if len(match.group()) % 2 == 0: + continue + + # Add a new part (up to the dot, exclusive) after escaping. + result.append( + ESCAPE_SEQUENCE_PATTERN.sub( + _escape_slash, field[prev_start : match.end() - 1] + ) + ) + prev_start = match.end() + + # Add any part of the field after the last unescaped dot. (Note that if the + # character is a dot this correctly adds a blank string.) + result.append(re.sub(r"\\(.)", _escape_slash, field[prev_start:])) + + return result + + def only_fields(dictionary: JsonDict, fields: List[str]) -> JsonDict: """Return a new dict with only the fields in 'dictionary' which are present in 'fields'. @@ -260,7 +310,7 @@ def only_fields(dictionary: JsonDict, fields: List[str]) -> JsonDict: If there are no event fields specified then all fields are included. The entries may include '.' characters 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 '\'. + A literal '.' or '\' character in a field name may be escaped using a '\'. Args: dictionary: The dictionary to read from. @@ -275,13 +325,7 @@ def only_fields(dictionary: JsonDict, fields: List[str]) -> JsonDict: # 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. - split_fields[:] = [ - [f.replace(r"\.", r".") for f in field_array] for field_array in split_fields - ] + split_fields = [_split_field(f) for f in fields] output: JsonDict = {} for field_array in split_fields: |