Make options tex_single_backslash_math and tex_double_backslash_math robust against extra spaces

[Witiko]

In #270, we added support for options tex_single_backslash_math and tex_double_backslash_math that add support for writing inline and display math between the separators \(, and \), \[, \] (for option tex_single_backslash_math) and \\(, and \\), \\[, \\] (for option tex_single_backslash_math):

$ docker run -i --rm witiko/markdown markdown-cli texMathSingleBackslash=true <<< '\( 1+2=3 \)'

\markdownRendererDocumentBegin
\markdownRendererInlineMath{1+2=3}\markdownRendererDocumentEnd

$ docker run -i --rm witiko/markdown markdown-cli texMathSingleBackslash=true <<< '\[ 1+2=3 \]'

\markdownRendererDocumentBegin
\markdownRendererDisplayMath{1+2=3}\markdownRendererDocumentEnd

$ docker run -i --rm witiko/markdown markdown-cli texMathDoubleBackslash=true <<< '\\( 1+2=3 \\)'

\markdownRendererDocumentBegin
\markdownRendererInlineMath{1+2=3}\markdownRendererDocumentEnd

$ docker run -i --rm witiko/markdown markdown-cli texMathDoubleBackslash=true <<< '\\[ 1+2=3 \\]'

\markdownRendererDocumentBegin
\markdownRendererDisplayMath{1+2=3}\markdownRendererDocumentEnd

However, introducing spaces around the separators produces unexpected results:

$ docker run -i --rm witiko/markdown markdown-cli texMathSingleBackslash=true <<< '\( 1+2=3 \)'

\markdownRendererDocumentBegin
( 1+2=3 )\markdownRendererDocumentEnd

$ docker run -i --rm witiko/markdown markdown-cli texMathSingleBackslash=true <<< '\[ 1+2=3 \]'

\markdownRendererDocumentBegin
[ 1+2=3 ]\markdownRendererDocumentEnd

$ docker run -i --rm witiko/markdown markdown-cli texMathDoubleBackslash=true <<< '\\( 1+2=3 \\)'

\markdownRendererDocumentBegin
\markdownRendererBackslash{}( 1+2=3 \markdownRendererBackslash{})\markdownRendererDocumentEnd

$ docker run -i --rm witiko/markdown markdown-cli texMathDoubleBackslash=true <<< '\\[ 1+2=3 \\]'

\markdownRendererDocumentBegin
\markdownRendererBackslash{}[ 1+2=3 \markdownRendererBackslash{}]\markdownRendererDocumentEnd

However, Pandoc does not reproduce the above results:

$ pandoc -f markdown+tex_math_single_backslash <<< '\( 1+2=3 \)'

<p><span class="math inline">1 + 2 = 3</span></p>

$ pandoc -f markdown+tex_math_single_backslash <<< '\[ 1+2=3 \]'

<p><br /><span class="math display">1 + 2 = 3</span><br /></p>

$ pandoc -f markdown+tex_math_double_backslash <<< '\\( 1+2=3 \\)'

<p><span class="math inline">1 + 2 = 3</span></p>

$ pandoc -f markdown+tex_math_double_backslash <<< '\\[ 1+2=3 \\]'

<p><br /><span class="math display">1 + 2 = 3</span><br /></p>

Acceptance criteria

• Update testfiles tests/testfiles/lunamark-markdown/tex-math-*backslash*.test with the above examples.
• Update the CommonMark parser to be robust against spaces around the separators.