Update the linter to also escape early for keywords having an unknown…

… parent

src/main/java/com/qindesign/json/schema/Linter.java

@@ -160,6 +160,19 @@ private static boolean is(List<String> path, String name) {
     return path.get(path.size() - 1).equals(name);
   }
 
+  /**
+   * Checks if the path ends with an unknown keyword.
+   *
+   * @param path the path
+   * @return whether the last element is unknown.
+   */
+  private static boolean isUnknown(List<String> path) {
+    if (path.isEmpty()) {
+      return false;
+    }
+    return !KNOWN_KEYWORDS.contains(path.get(path.size() - 1));
+  }
+
   /**
    * Checks the given schema and returns lists of any issues found for each
    * element in the tree. This returns a map of JSON element locations to a
@@ -290,8 +303,11 @@ public static Map<List<String>, List<String>> check(JsonElement schema) {
                  is(path, Definitions.NAME);
       }
 
-      // Allow anything directly below defs
-      if (inDefs) {
+      // Allow anything directly below defs or unknown keywords
+      // Note that arrays will have a path that ends in a number, and so is
+      // technically an unknown keyword; this is why we must also test for the
+      // parent being an array
+      if (inDefs || (isUnknown(path) && parent != null && !parent.isJsonArray())) {
         return;
       }