Properly handle newline escape sequences in strings for DOT (#3112)

* Properly handle newline escape sequences in strings for DOT

* Adjust comments in code

lib/network/dotparser.js

@@ -10,6 +10,29 @@
  * @return {Object} graph   An object containing two parameters:
  *                          {Object[]} nodes
  *                          {Object[]} edges
+ *
+ * -------------------------------------------
+ * TODO
+ * ====
+ *
+ * For label handling, this is an incomplete implementation. From docs (quote #3015):
+ * 
+ * > the escape sequences "\n", "\l" and "\r" divide the label into lines, centered, 
+ * > left-justified, and right-justified, respectively.
+ *
+ * Source: http://www.graphviz.org/content/attrs#kescString
+ *
+ * > As another aid for readability, dot allows double-quoted strings to span multiple physical
+ * > lines using the standard C convention of a backslash immediately preceding a newline
+ * > character
+ * > In addition, double-quoted strings can be concatenated using a '+' operator.
+ * > As HTML strings can contain newline characters, which are used solely for formatting,
+ * > the language does not allow escaped newlines or concatenation operators to be used
+ * > within them.
+ *
+ * - Currently, only '\\n' is handled
+ * - Note that text explicitly says 'labels'; the dot parser currently handles escape
+ *   sequences in **all** strings.
  */
 function parseDOT (data) {
   dot = data;
@@ -358,9 +381,14 @@ function getToken() {
   if (c === '"') {
     next();
     while (c != '' && (c != '"' || (c === '"' && nextPreview() === '"'))) {
-      token += c;
-      if (c === '"') { // skip the escape character
+      if (c === '"') {                                  // skip the escape character
+        token += c;
+        next();
+      } else if (c === '\\' && nextPreview() === 'n') { // Honor a newline escape sequence
+        token += '\n';
         next();
+      } else {
+        token += c;
       }
       next();
     }

test/dotparser.test.js

@@ -183,4 +183,78 @@ describe('dotparser', function () {
     });
   });
 
+
+  /**
+   * DOT-format examples taken from #3015
+   */
+  it('properly handles newline escape sequences in strings', function (done) {
+		var data = 'dinetwork {1 [label="new\\nline"];}';
+
+    data = String(data);
+
+    var graph = dot.parseDOT(data);
+
+    assert.deepEqual(graph, {
+      "id": "dinetwork",
+      "nodes": [
+        {
+          "id": 1,
+          "attr": {
+            "label": "new\nline",         // And not "new\\nline"
+          }
+        }
+      ]
+    });
+
+
+    // Note the double backslashes
+		var data2 = 'digraph {' + "\n" +
+'	3 [color="#0d2b7c", label="query:1230:add_q\\n0.005283\\n6.83%\\n(0.0001)\\n(0.13%)\\n17×"];' + "\n" +
+'	3 -> 7 [color="#0d2a7b", fontcolor="#0d2a7b", label="0.005128\\n6.63%\\n17×"];' + "\n" +
+'	5 [color="#0d1976", label="urlresolvers:537:reverse\\n0.00219\\n2.83%\\n(0.000193)\\n(0.25%)\\n29×"];' + "\n" +
+"}"
+
+    data2 = String(data2);
+
+    var graph2 = dot.parseDOT(data2);
+    //console.log(JSON.stringify(graph, null, 2));
+
+    assert.deepEqual(graph2, {
+      "type": "digraph",
+      "nodes": [
+        {
+          "id": 3,
+          "attr": {
+            "color": "#0d2b7c",
+            "label": "query:1230:add_q\n0.005283\n6.83%\n(0.0001)\n(0.13%)\n17×"
+          }
+        },
+        {
+          "id": 7
+        },
+        {
+          "id": 5,
+          "attr": {
+            "color": "#0d1976",
+            "label": "urlresolvers:537:reverse\n0.00219\n2.83%\n(0.000193)\n(0.25%)\n29×"
+          }
+        }
+      ],
+      "edges": [
+        {
+          "from": 3,
+          "to": 7,
+          "type": "->",
+          "attr": {
+            "color": "#0d2a7b",
+            "fontcolor": "#0d2a7b",
+            "label": "0.005128\n6.63%\n17×"
+          }
+        }
+      ]
+    });
+
+    done();
+  });
+
 });