feat(dashboard variables): allow custom values

[github-vincent-miszczak]

When working with dashboard variables, fields do not necessarily exist at the time of creation/manipulation(when importing a dashboard from JSON for instance, then editing a variable).

This feature keeps the existing behavior, but also allows custom values from user or JSON.

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Summary by cubic

Enable custom field names in the dashboard variable editor so variables work even when the field doesn’t exist yet (e.g., after importing from JSON). Replaces the field dropdown with a CompatibleCombobox that supports freeform entries and better loading UX.

• New Features
  • Switched to CompatibleCombobox (wrapper around @grafana/ui Combobox) with custom values via createCustomValue/onCreateOption.
  • Improved UX: "Select field" placeholder, empty -> null, loading via loading, keeps listing fetched fields, forwards onBlur.
  • On field change (selected or custom), immediately calls onChange with updated type, field, query, and limit.
  • Normalized fieldNames to { value, label, description? }; updated CHANGELOG.

^{Written for commit f06426c. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 1 file

[arturminchukov]

Thanks for contributing! Overall looks good. Left a few comments.

[github-vincent-miszczak]

@arturminchukov , thank you very much for the review.
I made changes following the comments, let me know if anything else needs adjustment.

[arturminchukov]

I've tested it locally. Looks like it doesn't work as expected and do not change the value in Combobox, because Grafana's Combobox do not call onBlur. I created a pr to the Grafana to fix it - grafana/grafana#121179.

Maybe you can change to deprecated Select right now. It should work.
Another option it remove onBlur handle and use onChange.
Could you please fix lint errors?

[cubic-dev-ai]

1 issue found across 21 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="src/language_provider.ts">

<violation number="1" location="src/language_provider.ts:112">
P2: getStreamFieldList ignores fieldValueFilter, so stream field value searches won’t be server-side filtered (unlike getFieldList), causing unfiltered/large results and broken search behavior.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review, or fix all with cubic.}

[github-vincent-miszczak]

@arturminchukov my update using CompatibleCombobox broke the feature. I restored using onChange looks better now.

[arturminchukov]

LGTM! Thanks for contributing!

[arturminchukov]

@github-vincent-miszczak Could you please sign your commits? Here, you can find a guide on how to do it.