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Mae LegaspiMae Legaspi 

Lightning Component Assertion Failed!: Provider type not supported : false

We have a VF page that basically just embeds a lightning component. We've been using this page for some time now, but then it just suddenly stopped working and showed the error: 
This page has an error. You might just need to refresh it. Assertion Failed!: Provider type not supported : false Failing descriptor: {c:LeadSearchBar}
Refreshing the page didn't help. Not sure if it's related, but I saw this on the console logs:
Failed to execute 'postMessage' on 'DOMWindow': The target origin provided ('https://ourcompany.lightning.force.com') does not match the recipient window's origin ('https://ourcompany.cs94.my.salesforce.com').
No error on the actual debug logs.

Then when I tried to create a Lightning App Page via the Lightning App Builder and incorporate the same lightning component we used on the VF page, I got the following error:
A Component Error has occurred!

Message: 
Assertion Failed!: Provider type not supported : false

Component Descriptor: 
markup://c:LeadSearchBar

Filename:
https://ourcompany.lightning.force.com/auraFW/javascript/m1kqsGvUD3kBv3RmG5pSKA/aura_prod.js

Function:
QA.log

Line:
237

Column:
157

Stack Trace:
QA.log()@https://ourcompany.lightning.force.com/auraFW/javascript/m1kqsGvUD3kBv3RmG5pSKA/aura_prod.js:237:157
$.z.assert()@https://ourcompany.lightning.force.com/auraFW/javascript/m1kqsGvUD3kBv3RmG5pSKA/aura_prod.js:784:397
a.P.Pd()@https://ourcompany.lightning.force.com/auraFW/javascript/m1kqsGvUD3kBv3RmG5pSKA/aura_prod.js:390:477
a.P [as constructor]()@https://ourcompany.lightning.force.com/auraFW/javascript/m1kqsGvUD3kBv3RmG5pSKA/aura_prod.js:388:428
new a()@https://ourcompany.lightning.force.com/auraFW/javascript/m1kqsGvUD3kBv3RmG5pSKA/aura_prod.js:275:254
V.Db()@https://ourcompany.lightning.force.com/auraFW/javascript/m1kqsGvUD3kBv3RmG5pSKA/aura_prod.js:639:465
a.z.Pd()@https://ourcompany.lightning.force.com/auraFW/javascript/m1kqsGvUD3kBv3RmG5pSKA/aura_prod.js:333:140

Is there an Aura update on Salesforce that could have possibly caused this? 

We didn't modify anything on our code base, and the error also suddenly appeared on our sandbox, which was created days before this happened. This is why we're thinking there must be some changes on Salesforce's side we're not aware of.
 
Best Answer chosen by Mae Legaspi
Mae LegaspiMae Legaspi
I did some brute force testing by deleting/commenting blocks of code at a time to determine the root cause of the error. I discovered that our former devs may have forgotten to put the "c." prefix when calling the action on the client-side controller. They used "onchange="{!clearSearch}"" instead of "onchange="{!c.clearSearch}"" inside the component code.

Looks like Salesforce enhanced their javascript QA tool that's why the error has been caught this time (tho it still kinda sucks that the error message and stack trace didn't really help). I guess our lightning component never really fully worked as expected before.

Thanks to everyone who took the time to read my post!

All Answers

Narender Singh(Nads)Narender Singh(Nads)
Hi,
I believe this is happening because the of the changes made to URL structure in the summer'1 release.
I might be able to help you if you could just share your code.
Mae LegaspiMae Legaspi
@Narender Singh(Nads) Sorry I wasn't able to post the code before because I still had to ask for permission. Fortunately, this case has been solved already. Thanks!
Mae LegaspiMae Legaspi
I did some brute force testing by deleting/commenting blocks of code at a time to determine the root cause of the error. I discovered that our former devs may have forgotten to put the "c." prefix when calling the action on the client-side controller. They used "onchange="{!clearSearch}"" instead of "onchange="{!c.clearSearch}"" inside the component code.

Looks like Salesforce enhanced their javascript QA tool that's why the error has been caught this time (tho it still kinda sucks that the error message and stack trace didn't really help). I guess our lightning component never really fully worked as expected before.

Thanks to everyone who took the time to read my post!
This was selected as the best answer
LemmingLemming
Just in case it helps someone, I got this error when I had accidentally upper-cased the "v" of a of component attribute in the .cmp of an aura component:
isLoading="{!V.isLoading}"
instead of:
isLoading="{!v.isLoading}"

 
Vijay MasneVijay Masne
boss Lemming u r just a best.