LWC EmpApi does not work when there is an Aura component using EmpApi

[AllanOricil]

Description

LWC can't subscribe to a Platform Event if there is an Aura component that is subscribing to a Platform event in the same Lightning Page.

Steps to Reproduce

Place an Aura component that subscribes to a Platform Event 1 and a LWC that subscribes to a Platform Event 2 in a Lightning Page. The Aura component subscribed without any problem. The LWC did not subscribe and also did not display any error message or exception. Once I removed the Aura component from the Lightning Page, saved it, and reloaded it, the LWC subscribed to the Platform Event. Bear in mind I did not change anything in the LWC. I just removed the Aura component from the Lightning Page.

I followed the instructions to build the LWC component from here:
https://developer.salesforce.com/docs/component-library/bundle/lightning-emp-api/documentation

And I made the correction to my component that is described here:
https://developer.salesforce.com/forums/ForumsMain?id=9062I000000Xm9eQAC

Again, the LWC code is working! but only if I remove the Aura component from the Lightning Page.

Expected Results

LWC should subscribe to the Platform Event

Actual Results

LWC does not subscribe to the Platform Event and also does not show an errror message or exception

[AllanOricil]

To solve my issue for now I just put my LWC into another Lightning Page. It works but an odd behavior happens.

When I load a page which has an Aura component that subscribes to a Platform Event using empApi and then move to another lightning page that has a LWC using empApi, this page throws an exception. If I reload this last lightning page the error is gone.

This is the exception that I have:

[miteshmsharma]

This was once happening with me and the reason for this was that upon the navigation the sequence of lifecycle events were not coordinated in the navigation logic. I used state to capture current and cleared the previous states altogether. If your component has state before the navigation I recommend to set it to the conducive state for the next component(page). The other thing which might be at play here is that you are going from an Aura component to LWC and if any of the event is set to bubble true then that might also be causing the call back within smartstore.customer bucket (Parent assumed hereas its ) that is probably due to a handled event down the container hierarchy not stopped explicitly by event.stopPropagation()

…

On Sat, Nov 16, 2019 at 10:18 PM AllanOricil ***@***.***> wrote: To solve my issue for now I just put my LWC into another Lightning Page. It works but an odd behavior happens. When I load a page which has an Aura component that subscribes to a Platform Event using empApi and then move to another lightning page that has a LWC using empApi, this page throws an exception. If I reload this last lightning page the error is gone. This is the exception that I have: [image: image] <https://user-images.githubusercontent.com/55927613/68996355-bdbfd500-0890-11ea-987b-dbd775f4faf3.png> — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#1618?email_source=notifications&email_token=ABRIU6FWRCHPDOJDRCQO3STQUAP4BA5CNFSM4JOFDGJKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEEHVQVQ#issuecomment-554653782>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABRIU6CFKF2NYURL6P5OXJ3QUAP4BANCNFSM4JOFDGJA> .

-- Regards Mitesh Sharma

[AllanOricil]

The components don't not communicate with each other! They are completly separated and both subscribe to different platform events. And both work when they are in separated Lightning Pages.
But if I switch from a Lightning page that has an Aura to a Lightning page that has the LWC it throws that above exception. Then if I reload the Lightning Page with the LWC the error is just gone...

My workaround was to transform my Aura to a LWC and everything worked perfectly. So my conclusion is, don't mix Aura and LWC components in a Lightning Page when they are both subscribing to Platform Events. This seems to be a bug.

[joeferraro]

We're having this exact same issue in console. Our steps to reproduce:

1. Open a console app
2. Open a console main tab that has a non-namespaced Aura component that subscribes to the empApi when it initializes
3. Open a separate console main tab that has a namespaced LWC component that subscribes to the empApi when a button is clicked
4. Click the button in the namespaced LWC component that subscribes to the empApi
5. Receive the following exception:

Method Promise.prototype.then called on incompatible receiver [object Object]

cc @cdelmoral @adamsheets89 @yippie

[caridy]

By looking at the error message, this seems like a problem with proxies. Promise.prototype.then expects a branded promise object, but it is receiving a proxy of it most likely, which is not branded. This could be locker service doing the wrong thing.

[joeferraro]

I have a suspicion this may have something to do with namespaces (at least in relation to the steps to reproduce I laid out above). I am unable to reproduce this issue when the Aura component subscribing is using the same namespace as the LWC component.

[caridy]

cc @seksenov @manuel-jasso to see if he can re-route this issue to the proper queue, this is definitely not LWC.

[manuel-jasso]

@seksenov @caridy Tracking on W-7429747

[vc4u]

Any updates on when this could be fixed? In my use case, I could reproduce this in Summer pre-release org as well.

My environment is set to use an already existing Background Utility Item Aura Component. And I'm building a new LWC component which needs to subscribe to a Change Data Event, now, both are conflicting, and LWC emp-api component is throwing the same error as mentioned above:

Method Promise.prototype.then called on incompatible receiver

[AllanOricil]

When I discovered this issue I wasn't using namespaces.

[arneper]

seeing exactly same issue even when it is only component on page. @AllanOricil
Thanks for any help!

[seksenov]

The Lightning Locker team is tracking and investigating the issue. When we have an update to share on potential resolutions and timeline we will do so.

[arneper]

@seksenov thanks! It is appreciated

[manuel-jasso]

Hi @AllanOricil, I am from Locker team, I would like to reproduce this issue, is there an environment you can point me to and steps to reproduce? Ideally, I would like to do that on my local, do you have a repo with code that I can clone and run? I understand this may be part of a large app, I'm just trying to see if we can narrow it down. Also looks like others like @joeferraro may have a similar/simpler way to reproduce?