Correctly produce paragraph separators inside block-level elements

[Witiko]

In #306, we added support for paragraph separators that are inserted between paragraphs and also between block-level element separated by more than one blank line:

markdown/markdown.dtx

Lines 28533 to 28570 in 859b8da

	Blocks = V("InitializeState")
	* ( V("ExpectedJekyllData")
	* (V("Blank")^0 / writer.interblocksep)
	)^-1
	* V("Blank")^0
	% \end{macrocode}
	% \par
	% \begin{markdown}
	%
	% Only create interblock separators between pairs of blocks that are not
	% both paragraphs. Between a pair of paragraphs, any number of blank
	% lines will always produce a paragraph separator.
	%
	% \end{markdown}
	% \begin{macrocode}
	* ( V("Block")
	* ( V("Blank")^0 * parsers.eof
	+ ( V("Blank")^2 / writer.paragraphsep
	+ V("Blank")^0 / writer.interblocksep
	)
	)
	+ ( V("Paragraph") + V("Plain") )
	* ( V("Blank")^0 * parsers.eof
	+ ( V("Blank")^2 / writer.paragraphsep
	+ V("Blank")^0 / writer.interblocksep
	)
	)
	* V("Block")
	* ( V("Blank")^0 * parsers.eof
	+ ( V("Blank")^2 / writer.paragraphsep
	+ V("Blank")^0 / writer.interblocksep
	)
	)
	+ ( V("Paragraph") + V("Plain") )
	* ( V("Blank")^0 * parsers.eof
	+ V("Blank")^0 / writer.paragraphsep
	)
	)^0,

Here is an example of two paragraphs that are correctly separated by paragraph separators rather than interblock separators:

$ docker run -i --rm witiko/markdown markdown-cli <<< $'First paragraph\n\nSecond paragraph'

\markdownRendererDocumentBegin
First paragraph\markdownRendererParagraphSeparator
Second paragraph\markdownRendererDocumentEnd

However, paragraph separators are not inserted between paragraphs in blockquotes:

$ docker run -i --rm witiko/markdown markdown-cli <<< $'> First paragraph\n>\n> Second paragraph'

\markdownRendererDocumentBegin
\markdownRendererBlockQuoteBegin
First paragraph\markdownRendererInterblockSeparator
Second paragraph
\markdownRendererBlockQuoteEnd \markdownRendererDocumentEnd

Furthermore, paragraph separators are also not inserted between paragraphs in fenced divs:

$ docker run -i --rm witiko/markdown markdown-cli fencedDivs=true <<< $'::: class\nFirst paragraph\n\nSecond paragraph\n:::'

\markdownRendererDocumentBegin
\markdownRendererFencedDivAttributeContextBegin
\markdownRendererAttributeClassName{class}%
First paragraph\markdownRendererInterblockSeparator
Second paragraph
\markdownRendererFencedDivAttributeContextEnd \markdownRendererDocumentEnd

Lastly, paragraph separators are also not inserted between paragraphs in lists:

$ docker run -i --rm witiko/markdown markdown-cli <<< $'- First paragraph\n\n  Second paragraph'

\markdownRendererDocumentBegin
\markdownRendererUlBegin
\markdownRendererUlItem First paragraph\markdownRendererInterblockSeparator
Second paragraph\markdownRendererUlItemEnd 
\markdownRendererUlEnd \markdownRendererDocumentEnd

$ docker run -i --rm witiko/markdown markdown-cli <<< $'1. First paragraph\n\n   Second paragraph'

\markdownRendererDocumentBegin
\markdownRendererOlBegin
\markdownRendererOlItemWithNumber{1}First paragraph\markdownRendererInterblockSeparator
Second paragraph\markdownRendererOlItemEnd 
\markdownRendererOlEnd \markdownRendererDocumentEnd

All four cases should produce paragraph separators instead.