Handlebars README and tooltip incorrectly state the available helpers

[sfirke]

Bug description

What's wrong in the "docs" + UI

The misleading documentation is at: https://github.com/apache/superset/blob/master/superset-frontend/plugins/plugin-chart-handlebars/README.md and in the UI, seen in the screenshot from this PR: #31998 (comment)

It lists only four helpers. But Superset imports a bunch more from just-handlebars-helpers. In particular I used eq extensively today. I think this matters because when I had Claude Code write code for the Handlebars Template, it avoided eq because of this README.md. But then I had it check the codebase, it found that it can use eq and others.

Some AI opinion (all the rest of this is me, a human)

Claude notes in diagnosing this issue:

🤖: PR #20648 (merged July 2022) added the just-handlebars-helpers module to the plugin. Then PR #21143 partially reverted it away from just-handlebars-helpers but registered helpers from [math, html, strings, conditionals] modules inline. The just-handlebars-helpers library includes eq (strict equality ===), eqw(weak equality==), neq, neqw, lt, lte, gt, gte, not, ifx, and, or, coalesce, and includes` among others.

Proposed fix

• This does not belong in a README.md buried deep in the repo. Realistically no one is going to find it there (except Claude, I guess). Let's move guidance about the Handlebars chart out to the user-facing section of the docs.
• Update the docs to describe all of the helpers available, at whatever level of detail we think is appropriate.
• Then remove the info tooltip? Or change it to be a link out to the new Handlebars Chart docs page you make

Screenshots/recordings

No response

Superset version

master / latest-dev

Python version

Not applicable

Node version

Not applicable

Browser

Not applicable

Additional context

No response

Checklist

• I have searched Superset docs and Slack and didn't find a solution to my problem.
• I have searched the GitHub issue tracker and didn't find a similar bug report.
• I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

[sfirke]

I marked this good first issue. If you are going to pick this up, please double-check the work and apply care to creating a Handlebars Chart page in the user-facing docs.

[Cloud-Architect-Emma]

Hi @sfirke, I’d like to work on this.

[sfirke]

Sure! Please start by checking out the user -facing drive docs section and thinking about where a Handlebars chart page (or subsection of another page) should go. The docs have gotten a massive reorganizion recently.

Feel free to ping me if you have questions as you go!