Make Nodes.find throw when not found

Author: robinst

commonmark/src/test/java/org/commonmark/test/ListBlockParserTest.java

@@ -60,7 +60,6 @@ public void testOrderedListIndents() {
     private void assertListItemIndents(String input, int expectedMarkerIndent, int expectedContentIndent) {
         Node doc = PARSER.parse(input);
         ListItem listItem = Nodes.find(doc, ListItem.class);
-        assertNotNull(listItem);
         assertEquals(expectedMarkerIndent, listItem.getMarkerIndent());
         assertEquals(expectedContentIndent, listItem.getContentIndent());
     }

commonmark/src/test/java/org/commonmark/test/Nodes.java

@@ -21,20 +21,32 @@ public static List<Node> getChildren(Node parent) {
      * @param parent    The node to get children from (node itself will not be checked)
      * @param nodeClass The type of node to find
      */
-    public static <T> T find(Node parent, Class<T> nodeClass) {
+    public static <T> T tryFind(Node parent, Class<T> nodeClass) {
         Node node = parent.getFirstChild();
         while (node != null) {
             Node next = node.getNext();
             if (nodeClass.isInstance(node)) {
                 //noinspection unchecked
                 return (T) node;
             }
-            T result = find(node, nodeClass);
+            T result = tryFind(node, nodeClass);
             if (result != null) {
                 return result;
             }
             node = next;
         }
         return null;
     }
+
+    /**
+     * Recursively try to find a node with the given type within the children of the specified node. Throw if node
+     * could not be found.
+     */
+    public static <T> T find(Node parent, Class<T> nodeClass) {
+        var node = tryFind(parent, nodeClass);
+        if (node == null) {
+            throw new IllegalArgumentException("Could not find a " + nodeClass.getSimpleName() + " node in " + parent);
+        }
+        return node;
+    }
 }

commonmark/src/test/java/org/commonmark/test/ThematicBreakParserTest.java

@@ -2,8 +2,6 @@
 
 import org.commonmark.node.ThematicBreak;
 import org.commonmark.parser.Parser;
-import org.commonmark.renderer.html.HtmlRenderer;
-import org.commonmark.testutil.RenderingTestCase;
 import org.junit.Test;
 
 import static org.junit.Assert.assertEquals;
@@ -23,7 +21,6 @@ public void testLiteral() {
 
     private static void assertLiteral(String expected, String input) {
         var tb = Nodes.find(PARSER.parse(input), ThematicBreak.class);
-        assertNotNull(tb);
         assertEquals(expected, tb.getLiteral());
     }
 }