passing query through grafana variable doesn't work anymore

[jenneron]

Our use case is to restrict table with some label, but also provide an option to append another query or search field from user input.

For example, we can match _AUDIT_LOGINUID:* *

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But we can't set $query to * and match _AUDIT_LOGINUID:* $query:

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I believe this is due to escape characters in resulting expression: expr:"_AUDIT_LOGINUID:* \"*\""

While this might be sufficient to provide a search field, it makes a wrong expression when the variable is empty: expr:"_AUDIT_LOGINUID:* \"\""

It works when downgrading the plugin to 0.3.0:

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The resulting query with 0.3.0: expr:"_AUDIT_LOGINUID:* *"

The resulting query with 0.3.0 and empty variable: expr:"_AUDIT_LOGINUID:* "