Fix spurious whitespace after inline \Sexpr[results=rd] (e.g. \doi{})

[ms609]

Fixes #2809.

\doi{10.2307/2413326}. renders as doi:10.2307/2413326 ., with a space between the link and the trailing full stop.

This PR was constructed with AI assistance; I have manually reviewed the modifications.

Root cause

\doi{} is a system Rd macro that expands (via \Sexpr[results=rd]) to an \ifelse/\href fragment. pkgdown's as_html.tag_Sexpr() evaluates that \Sexpr and re-parses the result as an Rd fragment with rd_text():

rd = flatten_text(rd_text(as.character(res))),

tools::parse_Rd(..., fragment = TRUE) appends a trailing newline TEXT node to every fragment. So the re-parsed doi fragment flattens to <a ...>doi:...</a>\n, and the following . ends up on the next line:

<a href='https://doi.org/10.2307/2413326'>doi:10.2307/2413326</a>\n.\n

The interior \n renders as whitespace in HTML. R's own Rd2HTML doesn't hit this because it expands the macro in place during a single parse rather than re-parsing the macro output as a separate fragment.

Any inline \Sexpr[results=rd]{} followed by punctuation is affected (not just DOIs).

Fix

The fix strips the trailing newline that fragment re-parsing adds, in the rd branch of as_html.tag_Sexpr():

rd = sub("\n$", "", flatten_text(rd_text(as.character(res)))),

This removes the node added by parse_Rd() without touching leading whitespace or valid \Sexpr content.

Tests

• Added a regression test in test-rd-html.R covering both \doi{...}. and a bare \Sexpr[results=rd]{...}..
• Updated the "Sexprs in file share environment" test: two adjacent inline \Sexpr now correctly render flush ("11") instead of being split across two lines by the newline artefact.

NEWS

• Inline \Sexpr[results=rd]{} (such as the \doi{} macro) no longer inserts
  spurious whitespace before following punctuation (pkgdown inserts white space after \doi{..} #2809).

[ms609]

Correct behaviour verified against real-world test cases.

CI failures seem to reflect unrelated stochastic tests rather than new errors caused by the fix?