Filtering on SchemaExtension properties still not possible for Outlook entities?

Question

So, I want to be able to fetch graph entites by an external guid and created a simple SchemaExtension "guid_custom" to achieve just that.

After updating some pre-existing event entities I'm able to verify this new extension works & is readable by including it in my query:

https://graph.microsoft.com/v1.0/me/events?$select=subject,guid_custom

... which fetches me several results like this one:

{
	"@odata.etag": "...",
	"id": "...",
	"subject": "test",
	"guid_custom": {
		"guid": "12c6571e-ef11-4ebe-b3e8-633072f799a3"
	}
}

However, trying to actually filter events on this extension property always results in an error:

https://graph.microsoft.com/v1.0/me/events?$filter=guid_custom/guid eq '{guid}'

  "error": {
        "code": "RequestBroker--ParseUri",
        "message": "Could not find a property named 'guid_custom' on type 'microsoft.graph.event'."
    }

I found some (several years) old posts claiming that filtering on schema extension properties was not possible for Outlook entity types then, all of them linking to this page:

https://learn.microsoft.com/en-us/graph/known-issues#filtering-on-schema-extension-properties-not-supported-on-all-entity-types

However, there's no mention of this restriction in the {current-year} version of this page, so I expect this should be resolved by now?

In this comparison overview table the docs clearly state that filtering should be possible:

https://learn.microsoft.com/en-us/graph/extensibility-overview?tabs=http#comparison-of-extension-types

So what is the status of this feature? Is this officially supported or not?

Answer 1

I am facing the same issue, the docs quite clearly state that filtering should be possible.