LaTeX writer: improve handling of math environments in tex math.

Previously the special handling added for #9711 worked only
when the math element did not contain spaces before the
math environment.

Closes #11266.

2 files changed, 26 insertions, 1 deletions

diff --git a/src/Text/Pandoc/Writers/LaTeX.hs b/src/Text/Pandoc/Writers/LaTeX.hs
index e10556cee..a0ecf687d 100644
--- a/src/Text/Pandoc/Writers/LaTeX.hs
+++ b/src/Text/Pandoc/Writers/LaTeX.hs
@@ -1375,7 +1375,7 @@ ldfLanguages =
 
 isMathEnv :: Text -> Bool
 isMathEnv t =
-  case T.stripPrefix "\\begin{" t of
+  case T.stripPrefix "\\begin{" (T.dropWhile isSpaceChar t) of
     Nothing -> False
     Just t' -> T.takeWhile (/= '}') t' `elem`
       [ "align", "align*"
@@ -1392,6 +1392,12 @@ isMathEnv t =
       , "eqnarray"
       , "displaymath"
       ]
+ where
+   isSpaceChar '\n' = True
+   isSpaceChar '\r' = True
+   isSpaceChar '\t' = True
+   isSpaceChar ' ' = True
+   isSpaceChar _ = False
 
 -- True if the math needs the cancel package
 needsCancel :: Text -> Bool
diff --git a/test/command/11266.md b/test/command/11266.md
new file mode 100644
index 000000000..e7c5ae73e
--- /dev/null
+++ b/test/command/11266.md
@@ -0,0 +1,19 @@
+```
+% pandoc -t latex
+$$
+\begin{eqnarray}
+S &\rightarrow& a A                      \nonumber \\
+A &\rightarrow& d B \ | \ b A \ | \ c A  \nonumber \\
+B &\rightarrow& a c \ | \ b C \ | \ c A  \nonumber \\
+C &\rightarrow& \epsilon                 \nonumber
+\end{eqnarray}
+$$
+^D
+
+\begin{eqnarray}
+S &\rightarrow& a A                      \nonumber \\
+A &\rightarrow& d B \ | \ b A \ | \ c A  \nonumber \\
+B &\rightarrow& a c \ | \ b C \ | \ c A  \nonumber \\
+C &\rightarrow& \epsilon                 \nonumber
+\end{eqnarray}
+```