Update theme template

[olivroy]

Intent

When previewing themes, it is not possible to preview how an inline function call looks or a string.

Since some themes show a different color for namespaced functions.
Also added a message to show the color of strings.

Approach

Modify template added in #13560

Automated Tests

N/A visual only when previewing themes

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.

Documentation

NA

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

Signed agreement

[kevinushey]

Thanks for the PR -- could you also share a screenshot of how the preview looks with your changes?

Can you also confirm the entire file contents are visible with a font size of 12? (I think we have a bit of room to expand the height of the preview if necessary)

[olivroy]

I don't really have a dev environment, I just edited the file as you added it in #13560.

There seems to be 4-5 empty lines at the end. As for the width, this line is the widest

  i <- c(n5, n4, n3, n2, n1)

The added lines do not exceed that width.

Currently:

I could include a screenshot with the impact of the changes when the next daily is available?

[kevinushey]

I wonder if there's a more realistic example we could use, since a typical R function like this wouldn't show messages.

Maybe we could add something like:

if (!is.numeric(x)) {
  stop("'x' must be a numeric vector")
}

to validate that x is a numeric vector?

[kevinushey]

This seems kind of arbitrary; I think the preview code we use should reflect "real" code as much as possible, and I don't think prefixing with base:: is common. I'm not sure if there's a better alternative. I think it's okay if we omit usages of :: in the preview here.

[olivroy]

I added a default of stats::rnorm(100), but if you are not convinced, that's okay, we can omit this.

I also added decreasing = FALSE to highlight how logical are shown