Resolve #7889 to avoid redundant checkpoint calls on loading notebook

[ikiw]

Resolve #7889 to avoid 3 fetch calls to load a notebook.

References

#7889

Code changes

listCheckpoints() gets invoked thrice when a notebook is loaded resulting in 3 checkpoint calls. The code change is to have an object- checkpointPromiseQueue that holds the promises with locaPath as key. If there is already a promise to be resolved, the pending promise object is returned back instead of creating one. And the promise reference to be cleared off from the checkpointPromiseQueue, when the promise if resolved/rejected via finally block. And as a result only 1 fetch call to checkpoint is triggered.

User-facing changes

Backwards-incompatible changes

NO

Before Fix

After Fix

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