Lightning Community Does Not Support pubsub for Lightning Web Components?

The pub-sub module checks for page references when firing events, so that the event is scoped and only in the current page.

In Communities, we actually now support lightning-navigation as of Spring '19: http://releasenotes.docs.salesforce.com/en-us/spring19/release-notes/rn_networks_navigationchanges.htm

However, there are some limitations, currently CurrentPageReference in LWC is not supported like: @wire(CurrentPageReference)currentPageReference;, which is why you are getting undefined page references. We are currently working on supporting it, so it should be out soon!

For a temporary solution, you can just remove all the pageRef checking in pubsub :). Here's a quick example: https://gist.github.com/kmesic/262887799fb70be94707cb0b87936e7b

Also, we are soon going to be releasing a LWC sample that will work in Communities by default! This should help clear up any confusion when using LWC in Communities.

Pub - Sub model uses Page reference and lightning-navigation and as lightning - navigation is supported only in Lightning Experience and Mobile App, the pub - sub module currently won't work in communities.

Src : https://github.com/trailheadapps/lwc-recipes/issues/86