Spec does not describe what the visibility conditions for a space or room in /hierarchy are

[reivilibre]

Link to problem area: https://spec.matrix.org/v1.5/client-server-api/#get_matrixclientv1roomsroomidhierarchy

Issue
From this description I can't find out what I need to do in order to ensure that a space I create will be visible to non-members in its parent space.
Or further, as a homeserver implementer I would have no idea what the conditions should be and I'd have to study Synapse source code I guess.

[reivilibre]

In matrix-org/synapse#14834 I dug up Synapse's definition:

Calculate whether the room should be shown to the requester.

It should return true if:

• The requesting local user is joined or can join the room (per MSC3173) — this typically means join_rules of public or knock; or
• The requesting remote homeserver has any user that is joined or can join the room; or
• The history visibility is set to world readable.

It's not clear how {guest_access: "can_join"} interacts here but the issue I'm working on — matrix-org/conference-bot#142 — suggests that it is needed in the space for things to work properly...

[clokep]

Duplicate of #1184.

To my memory this is not related to guest_access at all, but I might be forgetting something!

[clokep]

this typically means join_rules of public or knock; or

Or that the user fulfills one of the restricted join rule checks.

[turt2live]

Duplicate of #1184