Notebook Objects cannot be created with CouchDB enabled

[scottbell]

Summary

Creating a Notebook Object causes OpenMCT with CouchDB causes a "Save Failed" notification message in the UI, and an uncaught exception in the console:

Editor.js?3ce0:82 Uncaught (in promise) TypeError: Cannot read properties of null (reading 'cancel')
    at eval (Editor.js?3ce0:82)
    at new Promise (<anonymous>)
    at Editor.cancel (Editor.js?3ce0:80)
    at onCancel (CreateAction.js?95e8:71)
    at processQueue (angular.js?21b1:18075)
    at eval (angular.js?21b1:18123)
    at Scope.$digest (angular.js?21b1:19242)
    at eval (angular.js?21b1:19562)
    at TaskTracker.completeTask (angular.js?21b1:21403)
    at eval (angular.js?21b1:6879)

This prevents Notebook Objects from being used at all when CouchDB is enabled.

Expected vs Current Behavior

The Notebook Object should be created, saved into CouchDB, and updated with changes.

Impact Check List

• Data loss or misrepresented data?
• Regression? Did this used to work or has it always been broken?
• Is there a workaround available?
• Does this impact a critical component?
• Is this just a visual bug?

Steps to Reproduce

Enable CouchDB for OpenMCT:
https://github.com/nasa/openmct/blob/master/src/plugins/persistence/couch/README.md
Run OpenMCT and drop a Notebook Object.

Environment

• Open MCT Version: 1.7.8
• Deployment Type: npm dev
• OS: OSX
• Browser: Chrome

Additional Information

For a running investigation of this issue, see:
#3881 (comment)

Suffice to say, adding a null check here:
https://github.com/nasa/openmct/blob/master/src/plugins/persistence/couch/CouchObjectProvider.js#L373

return () => {
            if (this.observers[keyString]) {
                this.observers[keyString] = this.observers[keyString].filter(observer => observer !== callback);
                if (this.observers[keyString].length === 0) {
                    delete this.observers[keyString];
                    if (Object.keys(this.observers).length === 0 && this.isObservingObjectChanges()) {
                        this.stopObservingObjectChanges();
                    }
                }
            }
        };

seems to fix the issue.

[scottbell]

Created a PR for this issue here:
#4425

[nikhilmandlik]

Verified Fixed.

[shefalijoshi]

Verified fixed.

[charlesh88]

Verified fixed Testathon 11-15-21.