fix: return a null value for undefined nested keys

[SeanStove]

Since PR #4407 undefined nested keys throw an error message.
This might be helpful, but does not solve the issue when you have to work with data which looks like

[
  { "firstName": "John", "address": { "street": "Main street 1" } },
  { "firstName": "Jane", "address": null }
]

accessor address.street in this case will throw the error in dev.
(or will break the application later in production in case the data here is not as complete)

So the suggestion from @dennemark in issue #4499 makes sense to me.
This PR will return a null value, if the nested value does not exist.
Optionally, there could also be a console.warn statement with what used to be the error message.

Fixes: #4499

[KevinVandy]

I think we do need to do this, but let's also keep a console.warn with that error message in dev mode

[SeanStove]

I think we do need to do this, but let's also keep a console.warn with that error message in dev mode

@KevinVandy added the warning message.

[kachun333]

is it possible for this change to be merged, please?

[SeanStove]

I noticed the key in result will fail if the object is null, so I've added an additional check for that.

So it should now handle these cases:

{ "firstName": "Jane", "address": { "city": "New York" } }

{ "firstName": "James", "address": null }

{ "firstName": "Jimmy" }

when trying to access address.street

[KevinVandy]

should this be "===" triple equals equality check? and actually, wouldn't we want to check for undefined? Why is the result assignment moved to the last line?

[SeanStove]

I used "==" to handle both undefined and null, because you cannot use the in operator on either of them. Unless you want to handle undefined and null differently?

[KevinVandy]

@SeanStove I'm working on a PR where I'm simply making this change. Wonder if it works in your testing

accessorFn = (originalRow: TData) => {
        let result = originalRow as Record<string, any>

        for (const key of accessorKey.split('.')) {
          result = result?.[key]
          if (process.env.NODE_ENV !== 'production' && result === undefined) {
            console.warn(
              `"${key}" in deeply nested key "${accessorKey}" returned undefined.`
            )
          }
        }

        return result
      }

[SeanStove]

@KevinVandy Tested and it covers the 3 cases I described above. Thanks for this.

[KevinVandy]

Shipped this last week if you hadn't seen that yet

[KevinVandy]

shouldn't this still be above the if statement?

[SeanStove]

The result assignment is moved to the last line because you cannot read properties of null/undefined (which is covered by the if statement above it).

[KevinVandy]

This code was good, but cleaned up a little in this another PR. Closing this in favor of #4678