Org reader: More flexible LaTeX environments

Looking at the definition of `org-element-latex-environment-parser`, one
sees that Org allows arbitrary arguments to LaTeX environments. In fact,
it parses every char just after `\begin{xxx}` until `\end{xxx}` as
content for the environment, so all the following examples are valid
environments:

```org
\begin{equation} e = mc^2 \end{equations}
```
```org
\begin{tikzcd}[ampersand replacement=\&]
	A \& B \\
	C \& D
	\arrow[from=1-1, to=1-2]
	\arrow["f", from=2-1, to=2-2]
\end{tikzcd}
```

4 files changed, 29 insertions, 11 deletions

diff --git a/src/Text/Pandoc/Readers/Org/BlockStarts.hs b/src/Text/Pandoc/Readers/Org/BlockStarts.hs
index e5b2f7041..087819421 100644
--- a/src/Text/Pandoc/Readers/Org/BlockStarts.hs
+++ b/src/Text/Pandoc/Readers/Org/BlockStarts.hs
@@ -58,7 +58,6 @@ latexEnvStart = try $
   skipSpaces *> string "\\begin{"
              *> latexEnvName
              <* string "}"
-             <* blankline
  where
    latexEnvName :: Monad m => OrgParser m Text
    latexEnvName = try $ mappend <$> many1Char alphaNum <*> option "" (textStr "*")
diff --git a/src/Text/Pandoc/Readers/Org/Blocks.hs b/src/Text/Pandoc/Readers/Org/Blocks.hs
index 6b759901a..5fcafc703 100644
--- a/src/Text/Pandoc/Readers/Org/Blocks.hs
+++ b/src/Text/Pandoc/Readers/Org/Blocks.hs
@@ -36,7 +36,7 @@ import Control.Monad (foldM, guard, mplus, mzero, void)
 import Data.Char (isSpace)
 import Data.Default (Default)
 import Data.Functor (($>))
-import Data.List (foldl', intersperse)
+import Data.List (foldl')
 import Data.Maybe (fromMaybe, isJust, isNothing)
 import Data.Text (Text)
 import Data.List.NonEmpty (nonEmpty)
@@ -760,19 +760,17 @@ latexFragment = try $ do
   texOpt  <- getExportSetting exportWithLatex
   let envStart = "\\begin{" <> envName <> "}"
   let envEnd = "\\end{" <> envName <> "}"
-  envLines <- do
-    content <- manyTill anyLine (latexEnd envName)
-    return $ envStart : content ++ [envEnd]
+  envContent <- do
+    content <- manyTillChar anyChar (latexEnd envName)
+    return $ envStart <> content <> envEnd
   returnF $ case texOpt of
-    TeXExport -> B.rawBlock "latex" . T.unlines $ envLines
+    TeXExport -> B.rawBlock "latex" (envContent <> "\n")
     TeXIgnore   -> mempty
-    TeXVerbatim -> B.para . mconcat . intersperse B.softbreak $
-                   map B.str envLines
+    TeXVerbatim -> B.para . B.text $ envContent
  where
   latexEnd :: Monad m => Text -> OrgParser m ()
   latexEnd envName = try . void
-     $ skipSpaces
-    <* textStr ("\\end{" <> envName <> "}")
+     $ textStr ("\\end{" <> envName <> "}")
     <* blankline
 
 
diff --git a/test/Tests/Readers/Org/Block.hs b/test/Tests/Readers/Org/Block.hs
index 4f3038f93..fd11b9ad7 100644
--- a/test/Tests/Readers/Org/Block.hs
+++ b/test/Tests/Readers/Org/Block.hs
@@ -186,6 +186,27 @@ tests =
                , "\\end{equation}"
                ])
 
+    , "One-line LaTeX fragment" =:
+      "\\begin{equation} 2 + 3 \\end{equation}" =?>
+      rawBlock "latex" "\\begin{equation} 2 + 3 \\end{equation}\n"
+
+    , "LaTeX fragment with more arguments" =:
+      T.unlines [ "\\begin{tikzcd}[ampersand replacement=\\&]"
+                , "  A \\& B \\\\"
+                , "  C \\& D"
+                , "  \\arrow[from=1-1, to=1-2]"
+                , "  \\arrow[\"f\", from=2-1, to=2-2]"
+                , "\\end{tikzcd}"
+                ] =?>
+      rawBlock "latex"
+      (T.unlines [ "\\begin{tikzcd}[ampersand replacement=\\&]"
+                 , "  A \\& B \\\\"
+                 , "  C \\& D"
+                 , "  \\arrow[from=1-1, to=1-2]"
+                 , "  \\arrow[\"f\", from=2-1, to=2-2]"
+                 , "\\end{tikzcd}"
+                 ])
+
     , "Convert blank lines in blocks to single newlines" =:
       T.unlines [ "#+begin_html"
                 , ""
diff --git a/test/Tests/Readers/Org/Directive.hs b/test/Tests/Readers/Org/Directive.hs
index 7839cf193..cceed8108 100644
--- a/test/Tests/Readers/Org/Directive.hs
+++ b/test/Tests/Readers/Org/Directive.hs
@@ -250,7 +250,7 @@ tests =
                     , "\\end{equation}"
                     ] =?>
           para (str "\\begin{equation}" <> softbreak <>
-                str "f(x) = x^2" <> softbreak <>
+                text "f(x) = x^2" <> softbreak <>
                 str "\\end{equation}")
         ]
       ]