fix parsing cluster subgraph (fix #112)

Signed-off-by: Stefan Niederhauser <[email protected]>

Author: nidi3

graphviz-java/src/main/java/guru/nidi/graphviz/parse/Parser.java

@@ -131,7 +131,13 @@ private MutableGraph subgraph(boolean directed) {
             if (token.type == SUBGRAPH) {
                 nextToken();
                 if (token.type == ID) {
-                    sub.setName(label(token).toString());
+                    final String name = label(token).toString();
+                    if (name.startsWith("cluster_")) {
+                        sub.setName(name.substring(8));
+                        sub.setCluster(true);
+                    } else {
+                        sub.setName(name);
+                    }
                     nextToken();
                 }
             }

graphviz-java/src/test/java/guru/nidi/graphviz/parse/ParserTest.java

@@ -135,4 +135,10 @@ void multiLinkAttr() throws IOException {
         assertEquals(mutGraph().add(a, b),
                 Parser.read("graph { edge[color=red, width=1] a -- b edge[color=blue, a=b] a -- b }"));
     }
+
+    @Test
+    void cluster() throws IOException {
+        assertEquals(mutGraph().add(mutGraph("sub").setCluster(true)),
+                Parser.read("graph { subgraph cluster_sub {} }"));
+    }
 }