Dashboards: Skip inherited object variable names

[jarben]

What is this feature?

This PR fixes an issue where variables containing inherited object property names fail with TypeError: T[Q].add is not a function here. This issue has been reported in this escalation.

This is because if (varName! in panelsByVar) { returns true for any variable name that matches inherited prop names.

We can potentially use if (panelsByVar.hasOwnProperty(varName)); however, this would add variables such as toString and would fail anyway as reported here and [here](https://github.com/grafana/grafana/issues/67342).

Which issue(s) does this PR fix?:
Fixes https://github.com/grafana/support-escalations/issues/8743

Also relates to: https://community.grafana.com/t/error-updating-options-t-e-add-is-not-a-function/71728/7

Special notes for your reviewer:

Please check that:

• It works as expected from a user's perspective.
• If this is a pre-GA feature, it is behind a feature toggle.
• The docs are updated, and if this is a notable improvement, it's added to our What's New doc.

[axelavargas]

Hey @jarben 😄 , great attempt to fix this issue. Because our variable system is complex, I would like to gain more context of the original escalation, would you mind sharing a dashboard example where the escalation issue can be reproduced?

So far, I tested your branch locally, taking the use case from the other related issue: #79212 (using $toString in a query variable), and I still see the problem.

toStringStillTriggersJsError.mp4

I believe the reason is the getVariableName from inspect/utils is not the same function we are using when we are interpolating variables(getTemplateSrv().replace).

[jarben]

Hi @Alexa Vargas, thanks for looking at this! The issue can be reproduced here. You can add yourself to the org by adding your email to staff membership here.

[jarben]

I believe the reason is the getVariableName from inspect/utils is not the same function we are using when we are interpolating variables(getTemplateSrv().replace).

Good point @axelavargas , this would prevent the error to appear:

Although I wonder if we want the variable to not show at all here?

[axelavargas]

Hey @jarben 😄 , Thanks for granting me access to the original issue.

I have tested on my local machine a dashboard with Mongo DB and variables and works as expected, the errors disappeared 🥳 .

VariablesMongoWorkingAgain.mp4

Also Issues 67342 and 79212 are still unresolved, and I am afraid the change you suggested in the getVariabledAtIndex will not work as should be. We will prevent showing the error, but the expected behavior should be to do the query by taking the $toString as a normal string. After researching, I found we don't support escaping variable expressions in the query, check this issue #40603 .

I think your PR will only fix the issue from the escalation 🙌🏾 . However, we will need to tackle the other ones in another PR (A bit challenging to be honest with the current variable system)