When converting native -> markdown (with tex_math_dollars), DisplayMath that contains leading/trailing newlines is now emitted as a single-line $$...$$ in pandoc 3.7+, whereas pandoc 3.6.4 preserved the internal newlines:

• pandoc 3.6.4 (previous behavior)

  $$
  e = mc^2
  $$
  

• pandoc 3.7+ (actual)

  $$e = mc^2$$
  

This breaks use-cases where consumers expect a multi-line display-math block (for example: producing Markdown for tools like remark/remark-math + KaTeX or Docusaurus MDX that treat $$\n...\n$$ as a block).

Here is how to reproduce

1. Start pandoc in native mode to build the test Inline element (or use a file containing display math with surrounding blank lines):

   ❯ pandoc -f native -t markdown
   [ Para [ Math DisplayMath "\ne = mc^2\n" ] ]
   ^D
   

2. Observe output in 3.6.4:

   $$
   e = mc^2
   $$
   

   Observe output in 3.7:

   $$e = mc^2$$
   

Looking at history I found what changed this.

Before 3.7 the Markdown writer used simple concatenation for $$ display math (effectively "$$" <> literal str <> "$$"). In 3.7 the writer now uses the new delimited helper which pulls leading/trailing whitespace (including newlines) outside the opener/closer.

The delimited function intentionally extracts initial and trailing whitespace (NewLine, CarriageReturn, BreakingSpace, BlankLines) and places it outside the opener/closer. That behavior is often useful for inline delimiters (emphasis, code markers, etc.) but has the side effect of removing the interior newlines for display math when the tex_math_dollars path uses delimited "$$" "$$" (literal str). So I wonder if this is expected change for display math block ?

This is a problem for some Markdown toolchains that distinguish between:

• block display math: $$\n<math>\n$$ (treated as a block)
• inline math: $<math>$ or single-line $$<math>$$ (treated inline)

Converting a display math block to $$<math>$$ can change rendering from block-centered math to inline math, breaking layout.

Context

• I originally noticed this while generating Markdown for Docusaurus / MDX with remark-math + KaTeX. The single-line $$...$$ is interpreted as inline math by the toolchain and not displayed as a centered block.
• I believe previous behavior in 3.6.4 preserved the internal newlines for DisplayMath; the change to delimited in 3.7 appears to have caused this regression.