61 lines
2.4 KiB
Markdown
61 lines
2.4 KiB
Markdown
# MSC3980: Dotted Field Consistency
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[MSC3873](https://github.com/matrix-org/matrix-spec-proposals/pull/3873) disambiguated
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how event properties are matched for push rules and based the proposal on how
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[filters](https://spec.matrix.org/v1.6/client-server-api/#post_matrixclientv3useruseridfilter)
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are currently escaped for consistency.
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Through the MSC process the escaping was expanded from just escaping `.` characters
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with a backslash (`\.`) to also escaping backslashes themselves (`\\`). Unfortunately
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that MSC did not propose applying this change *back* to filters for consistency. [^1]
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## Proposal
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Apply consistent escaping as described in [MSC3873](https://github.com/matrix-org/matrix-spec-proposals/pull/3873)
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to the `event_fields` property of filters.
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This would allow an unambiguous way to describe property names, as currently
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the behavior of backslashes is undefined.
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The text given in MSC3873 can apply here (changing `key` to `event_fields`):
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> The dot (`.`) character in the [`event_fields`] parameter is changed to be exclusively
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reserved for field separators. Any literal dot in field names are to be
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escaped using a backslash (`\.`) and any literal backslashes are also escaped with
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a backslash (`\\`). A backslash before any other character has no special meaning
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and is left as-is, but it is recommended that implementations do not redundantly
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escape characters, as they may be used for escape sequences in the future.
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In short, this would update the
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[description of `event_fields`](https://spec.matrix.org/v1.6/client-server-api/#post_matrixclientv3useruseridfilter)
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(bolded part is new):
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> List of event fields to include. If this list is absent then all fields are
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> included. The entries may include ‘.’ characters to indicate sub-fields. So
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> [‘content.body’] will include the ‘body’ field of the ‘content’ object. A
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> literal ‘.’ **or '\\'** character in a field name may be escaped using a ‘\’. A server
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> may include more fields than were requested.
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## Potential issues
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This is slightly backwards incompatible if a property name currently contains a
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backslash in it.
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## Alternatives
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Leave things as they are and be inconsistent between different parts of the spec.
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## Security considerations
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N/A
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## Unstable prefix
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N/A
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## Dependencies
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N/A
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[^1]: This came up while writing the [spec PR for MSC3873](https://github.com/matrix-org/matrix-spec/pull/1464#discussion_r1135712844).
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