Write id for code block to label attr in latex when listing is used

The code:

    ~~~{#test}
    asdf
    ~~~

gets compiled to html:

    <pre id="test">
    asdf
    </pre>

So it is possible to link to the identifier `test`

But this doesn't happen on latex

When using the listings package (`--listings`) it is possible to set the
identifier using the `label=test` property:

    \begin{lstlisting}[label=id]
    hi
    \end{lstlisting}

And this is exactly what this patch is doing.

Modified LaTeX Reader/Writer and added tests for this.

2 files changed, 14 insertions, 0 deletions

diff --git a/tests/Tests/Readers/LaTeX.hs b/tests/Tests/Readers/LaTeX.hs
index 88029b7c2..dff6e4537 100644
--- a/tests/Tests/Readers/LaTeX.hs
+++ b/tests/Tests/Readers/LaTeX.hs
@@ -55,6 +55,13 @@ tests = [ testGroup "basic"
             "hi % this is a comment\nthere\n" =?> para "hi there"
           ]
 
+        , testGroup "code blocks"
+          [ "identifier" =:
+            "\\begin{lstlisting}[label=test]\\end{lstlisting}" =?> codeBlockWith ("test", [], [("label","test")]) ""
+          , "no identifier" =:
+            "\\begin{lstlisting}\\end{lstlisting}" =?> codeBlock ""
+          ]
+
         , testGroup "citations"
           [ natbibCitations
           , biblatexCitations
diff --git a/tests/Tests/Writers/LaTeX.hs b/tests/Tests/Writers/LaTeX.hs
index ebde5b97c..5f702a85d 100644
--- a/tests/Tests/Writers/LaTeX.hs
+++ b/tests/Tests/Writers/LaTeX.hs
@@ -10,6 +10,9 @@ import Tests.Arbitrary()
 latex :: (ToString a, ToPandoc a) => a -> String
 latex = writeLaTeX def . toPandoc
 
+latexListing :: (ToString a, ToPandoc a) => a -> String
+latexListing = writeLaTeX def{ writerListings = True } . toPandoc
+
 {-
   "my test" =: X =?> Y
 
@@ -31,6 +34,10 @@ tests :: [Test]
 tests = [ testGroup "code blocks"
           [ "in footnotes" =: note (para "hi" <> codeBlock "hi") =?>
             "\\footnote{hi\n\n\\begin{Verbatim}\nhi\n\\end{Verbatim}\n}"
+          , test latexListing "identifier" $ codeBlockWith ("id",[],[]) "hi" =?>
+            ("\\begin{lstlisting}[label=id]\nhi\n\\end{lstlisting}" :: String)
+          , test latexListing "no identifier" $ codeBlock "hi" =?>
+            ("\\begin{lstlisting}\nhi\n\\end{lstlisting}" :: String)
           ]
         , testGroup "math"
           [ "escape |" =: para (math "\\sigma|_{\\{x\\}}") =?>