Merge 1baf93caf5 into 8ebf4a4789

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

changelogs/client_server/newsfragments/2240.clarification

@@ -0,0 +1 @@
+Clarify how to use `state_after` ahead of declaring full support for its spec version.

changelogs/client_server/newsfragments/2245.clarification

@@ -0,0 +1 @@
+`device_one_time_keys_count` is only optional if no unclaimed one-time keys exist.

changelogs/internal/newsfragments/2222.clarification

@@ -0,0 +1 @@
+Clarify vendor prefixing requirements.

content/client-server-api/modules/end_to_end_encryption.md

@@ -1775,19 +1775,18 @@ property is required for inclusion, though previous versions of the
 specification did not have it. In addition to `/versions`, this can be
 a way to identify the server's support for fallback keys.
 
-
-| Parameter                        | Type               | Description                                                                                                            |
-|----------------------------------|--------------------|------------------------------------------------------------------------------------------------------------------------|
-| device_lists                     | DeviceLists        | Optional. Information on e2e device updates. Note: only present on an incremental sync.                                |
-| device_one_time_keys_count       | {string: integer}  | Optional. For each key algorithm, the number of unclaimed one-time keys currently held on the server for this device.  If an algorithm is unlisted, the count for that algorithm is assumed to be zero.  If this entire parameter is missing, the count for all algorithms is assumed to be zero.  |
-| device_unused_fallback_key_types | [string]           | **Required.** The unused fallback key algorithms.                                                                      |
+| Parameter                        | Type              | Description                                                                                                            |
+|----------------------------------|-------------------|------------------------------------------------------------------------------------------------------------------------|
+| device_lists                     | DeviceLists       | Optional. Information on e2e device updates. Note: only present on an incremental sync.                                |
+| device_one_time_keys_count       | {string: integer} | **Required if any unclaimed one-time keys exist.** For each key algorithm, the number of unclaimed one-time keys currently held on the server for this device. If the count for an algorithm is zero, servers MAY omit that algorithm. If the count for all algorithms is zero, servers MAY omit this parameter entirely. |
+| device_unused_fallback_key_types | [string]          | **Required.** The unused fallback key algorithms.                                                                      |
 
 `DeviceLists`
 
-| Parameter  | Type      | Description                                                                                                                                                      |
-|------------|-----------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| changed    | [string]  | List of users who have updated their device identity or cross-signing keys, or who now share an encrypted room with the client since the previous sync response. |
-| left       | [string]  | List of users with whom we do not share any encrypted rooms anymore since the previous sync response.                                                            |
+| Parameter | Type     | Description                                                                                                                                                      |
+|-----------|----------|------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| changed   | [string] | List of users who have updated their device identity or cross-signing keys, or who now share an encrypted room with the client since the previous sync response. |
+| left      | [string] | List of users with whom we do not share any encrypted rooms anymore since the previous sync response.                                                            |
 
 {{% boxes/note %}}
 For optimal performance, Alice should be added to `changed` in Bob's

content/proposals.md

@@ -408,41 +408,9 @@ development or testing data.
 that a particular MSC works) do not have to follow this process.
 
 1.  Have an idea for a feature.
-1.  Implement the feature using unstable endpoints, vendor prefixes, and
-    unstable feature flags as appropriate.
-    -   When using unstable endpoints, they MUST include a vendor
-        prefix. For example:
-        `/_matrix/client/unstable/com.example/login`. Vendor prefixes
-        throughout Matrix always use the Java package naming convention.
-        The MSC for the feature should identify which preferred vendor
-        prefix is to be used by early adopters.
-    -   Note that unstable namespaces do not automatically inherit
-        endpoints from stable namespaces: for example, the fact that
-        `/_matrix/client/r0/sync` exists does not imply that
-        `/_matrix/client/unstable/com.example/sync` exists.
-    -   If the client needs to be sure the server supports the feature,
-        an unstable feature flag that MUST be vendor prefixed is to be
-        used. This kind of flag shows up in the `unstable_features`
-        section of `/versions` as, for example, `com.example.new_login`.
-        The MSC for the feature should identify which preferred feature
-        flag is to be used by early adopters.
-    -   When using this approach correctly, the implementation can
-        ship/release the feature at any time, so long as the
-        implementation is able to accept the technical debt that results
-        from needing to provide adequate backwards and forwards
-        compatibility. The implementation MUST support the flag (and
-        server-side implementation) disappearing and be generally safe
-        for users. Note that implementations early in the MSC review
-        process may also be required to provide backwards compatibility
-        with earlier editions of the proposal.
-    -   If the implementation cannot support the technical debt (or if
-        it's impossible to provide forwards/backwards compatibility -
-        e.g. a user authentication change which can't be safely rolled
-        back), the implementation should not attempt to implement the
-        feature and should instead wait for a spec release.
-    -   If at any point after early release, the idea changes in a
-        backwards-incompatible way, the feature flag should also change
-        so that implementations can adapt as needed.
+1.  Implement the feature using [unstable endpoints, vendor prefixes, and
+    unstable feature flags](#unstable-endpoints-features-and-vendor-prefixes)
+    as appropriate.
 1.  In parallel, or ahead of implementation, open an MSC and solicit
     review per above.
 1.  Before FCP can be called, the Spec Core Team will require evidence
@@ -452,10 +420,7 @@ that a particular MSC works) do not have to follow this process.
     forwards/backwards compatibility concerns mentioned here.
 1.  The FCP process is completed, and assuming nothing is flagged the
     MSC lands.
-1.  Implementations can now switch to using stable prefixes
-    (for example, for an endpoint, moving from
-    `/unstable/org.matrix.mscxxxx/frobnicate`
-    to `/v1/frobnicate`), assuming that the change
+1.  Implementations can now switch to using stable prefixes, assuming that the change
     is backwards compatible with older implementations. In the rare occasion
     where backwards compatibility is not possible without a new spec release,
     implementations should continue to use unstable prefixes.
@@ -471,13 +436,6 @@ that a particular MSC works) do not have to follow this process.
     started supporting the new spec release, some noise should be raised
     in the general direction of the implementation.
 
-{{% boxes/note %}}
-MSCs MUST still describe what the stable endpoints/feature looks like
-with a note towards the bottom for what the unstable feature
-flag/prefixes are. For example, an MSC would propose `/_matrix/client/r0/new/endpoint`, not `/_matrix/client/unstable/
-com.example/new/endpoint`.
-{{% /boxes/note %}}
-
 In summary:
 
 -   Implementations MUST NOT use stable endpoints before the MSC has
@@ -489,14 +447,90 @@ In summary:
 -   Implementations SHOULD be wary of the technical debt they are
     incurring by moving faster than the spec.
 -   The vendor prefix is chosen by the developer of the feature, using
-    the Java package naming convention. The foundation's preferred
-    vendor prefix is `org.matrix`.
+    the Java package naming convention.
 -   The vendor prefixes, unstable feature flags, and unstable endpoints
     should be included in the MSC, though the MSC MUST be written in a
     way that proposes new stable endpoints. Typically this is solved by
     a small table at the bottom mapping the various values from stable
     to unstable.
 
+#### Unstable endpoints, features and vendor prefixes
+
+Unstable endpoints MUST use `/unstable` as the endpoint version and a
+vendor prefix in Java package naming format. For example:
+`/_matrix/client/unstable/com.example.mscxxxx/login`.
+
+{{% boxes/note %}}
+Proposal authors operating with a Matrix.org Foundation mandate SHOULD use
+a vendor prefix within the `org.matrix` namespace. This namespace is otherwise
+restricted. Authors who don't own a domain MAY use the `io.github` namespace
+instead.
+{{% /boxes/note %}}
+
+Note that unstable namespaces do not automatically inherit endpoints from
+stable namespaces: for example, the fact that `/_matrix/client/v3/sync`
+exists does not imply that `/_matrix/client/unstable/com.example.mscxxxx/sync`
+exists.
+
+Vendor prefixes MUST also be used for:
+
+-   New parameters on existing endpoints. For example:
+    `/_matrix/client/v3/publicRooms?com.example.mscxxxx.ordered_by=member_count`.
+-   New properties in existing JSON objects. For example:
+
+    ```json
+    {
+      "avatar_url": "mxc://matrix.org/SDGdghriugerRg",
+      "displayname": "Alice Margatroid",
+      "com.example.mscxxxx.phone": [{
+        "type": "landline",
+        "number": "+1-206-555-7000"
+      }],
+      ...
+    }
+    ```
+
+-   New values for existing parameters or properties. For example:
+
+    ```json
+    {
+      "errcode": "COM.EXAMPLE.MSCXXXX.M_INVALID_EMAIL",
+      "error": "The email address you provided is invalid."
+    }
+    ```
+
+If the client needs to be sure the server supports the feature, an
+unstable feature flag that MUST also be vendor prefixed is to be used.
+This flag shows up in the `unstable_features` section of
+[`/_matrix/client/versions`](/client-server-api/#get_matrixclientversions)
+as, for example, `com.example.mscxxxx.new_login`.
+
+{{% boxes/note %}}
+MSCs MUST still describe what the stable endpoints/feature looks like
+with a note towards the bottom for what the unstable feature
+flag/prefixes are. For example, an MSC would propose `/_matrix/client/v1/new/endpoint`,
+not `/_matrix/client/unstable/com.example.mscxxxx/new/endpoint`.
+{{% /boxes/note %}}
+
+When using this approach correctly, the implementation can release
+the feature at any time, so long as the implementation is able to
+accept the technical debt that results from needing to provide
+adequate backwards and forwards compatibility. The implementation
+MUST support the flag (and server-side implementation) disappearing
+and be generally safe for users. Note that implementations early in
+the MSC review process may also be required to provide backwards
+compatibility with earlier editions of the proposal.
+
+If the implementation cannot support the technical debt (or if it's
+impossible to provide forwards/backwards compatibility - e.g. a user
+authentication change which can't be safely rolled back), the
+implementation should not attempt to implement the feature and should
+instead wait for a spec release.
+
+If at any point after early release, the idea changes in a
+backwards-incompatible way, the feature flag should also change so
+that implementations can adapt as needed.
+
 ### Placeholder MSCs
 
 Some proposals may contain security-sensitive or private context which can't be

data/api/client-server/sync.yaml

@@ -133,10 +133,15 @@ paths:
             sync and the **start** of the timeline in `state` and MUST omit
             `state_after`.
 
-            Even if this is set to `true`, clients MUST update their local state
-            with events in `state` and `timeline` if `state_after` is missing in
-            the response, for compatibility with servers that don't support this
-            parameter.
+            Servers MAY implement this parameter ahead of declaring support for
+            the version of the spec in which it was introduced. Consequently,
+            clients MAY set this parameter to `true` regardless of the
+            [`/versions`](/client-server-api/#get_matrixclientversions) response.
+            If they do, they can infer whether the server actually supports this
+            parameter from the presence of `state_after` in the response. If
+            `state_after` is missing, clients MUST behave as if they had not
+            specified the parameter and update their local state with events
+            in `state` and `timeline`.
 
             By default, this is `false`.
           example: false