LaTeX reader: fix spurious paragraph breaks in math environments (#11265)

Previously, a math environment with extra space before the
`\end` would get rendered with a blank line, which LaTeX
treats as a paragraph break.

Signed-off-by: Emmanuel Ferdman <[email protected]>

2 files changed, 40 insertions, 2 deletions

diff --git a/src/Text/Pandoc/Readers/LaTeX/Math.hs b/src/Text/Pandoc/Readers/LaTeX/Math.hs
index 1f4dc4f8c..f1491656e 100644
--- a/src/Text/Pandoc/Readers/LaTeX/Math.hs
+++ b/src/Text/Pandoc/Readers/LaTeX/Math.hs
@@ -21,7 +21,7 @@ import qualified Data.Sequence as Seq
 import Text.Pandoc.Readers.LaTeX.Parsing
 import Text.Pandoc.TeX
 import Text.Pandoc.Class
-import Text.Pandoc.Shared (trimMath, stripTrailingNewlines)
+import Text.Pandoc.Shared (trimMath, trimr)
 import Text.Pandoc.Parsing hiding (blankline, mathDisplay, mathInline,
                             optional, space, spaces, withRaw, (<|>))
 import Control.Applicative ((<|>), optional)
@@ -82,7 +82,7 @@ mathEnv :: PandocMonad m => Text -> LP m Text
 mathEnv name = withMathMode $ do
   optional blankline
   res <- manyTill anyTok (end_ name)
-  return $ stripTrailingNewlines $ untokenize res
+  return $ trimr $ untokenize res
 
 inlineEnvironment :: PandocMonad m => LP m Inlines
 inlineEnvironment = try $ do
diff --git a/test/command/latex-math-trailing-space.md b/test/command/latex-math-trailing-space.md
new file mode 100644
index 000000000..6502b120a
--- /dev/null
+++ b/test/command/latex-math-trailing-space.md
@@ -0,0 +1,38 @@
+Test that trailing spaces before \end{equation} don't create spurious paragraph breaks:
+
+```
+% pandoc -f latex -t latex
+\begin{equation}
+  a
+ \end{equation}
+^D
+\begin{equation}
+  a
+\end{equation}
+```
+
+Same for align environment:
+
+```
+% pandoc -f latex -t latex
+\begin{align}
+  x &= y \\
+ \end{align}
+^D
+\begin{align}
+  x &= y \\
+\end{align}
+```
+
+Test with multiple trailing spaces:
+
+```
+% pandoc -f latex -t latex
+\begin{equation}
+  a + b
+   \end{equation}
+^D
+\begin{equation}
+  a + b
+\end{equation}
+```