[poc] embed html widgets in the console

[romainfrancois]

Intent

display html widgets directly in the console. This may be useful for e.g. error messages, e.g. r-lib/rlang#1440

Approach

.rs.api.console_viewer() similar to .rs.api.viewer() (for widgets) but the rsult goes i the console:

Automated Tests

Indicate whether this change includes unit tests or integration tests, or link a work item or pull request to add those tests to another repo. If the change cannot or will not be covered by a test, indicate why.

QA Notes

Add additional information for QA on how to validate the change, paying special attention to the level of risk, adjacent areas that could be affected by the change, and any important contextual information not present in the linked issues.

Checklist

• If this PR adds a new feature, or fixes a bug in a previously released version, it includes an entry in NEWS.md
• If this PR adds or changes UI, the updated UI meets accessibility standards
• A reviewer is assigned to this PR (if unsure who to assign, check Area Owners list)
• This PR passes all local unit tests

[romainfrancois]

This is still very rough, but if we get this to work, then it's just a matter of writing some htmltools ui code.

[kevinushey]

Overall LGTM!

One open question: do these widgets need to be persisted in some way in the console history, or do we need any special handling there? This is mainly relevant to RStudio Server, where we need to persist the console history for the user in case they reload the browser (or close and then later reconnect).

It's probably fine if we don't do anything here but worth testing to make sure that these widgets don't break anything (just in case).

[kevinushey]

Is this comment still true?

[kevinushey]

Nit: if there's only one "target" code path you could probably reduce the indentation in this function with some early returns for cases where validity conditions aren't satisfied.

[romainfrancois]

Maybe the widgets should get some surrounding like results = "asis" in Rmd:

[romainfrancois]

👀 .rs.recordHtmlWidget()

[romainfrancois]

shelving this for now to declutter the pull requests, we may come back to this later, so keeping the branch just in case.