MarkdownRenderer: Fix overriding of core rendering

CHANGELOG.md

@@ -6,6 +6,13 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 This project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html),
 with the exception that 0.x versions can break between minor versions.
 
+## [Unreleased]
+### Added
+### Changed
+### Fixed
+- `MarkdownRenderer`: Fix precedence for `nodeRendererFactory`: Factories passed
+  to the builder can now override rendering for core node types.
+
 ## [0.24.0] - 2024-10-21
 ### Added
 - `SourceSpan` on nodes now have a `getInputIndex` to get the index within the
@@ -459,6 +466,7 @@ API breaking changes (caused by changes in spec):
 Initial release of commonmark-java, a port of commonmark.js with extensions
 for autolinking URLs, GitHub flavored strikethrough and tables.
 
+[Unreleased]: https://github.com/commonmark/commonmark-java/compare/commonmark-parent-0.24.0...main
 [0.24.0]: https://github.com/commonmark/commonmark-java/compare/commonmark-parent-0.23.0...commonmark-parent-0.24.0
 [0.23.0]: https://github.com/commonmark/commonmark-java/compare/commonmark-parent-0.22.0...commonmark-parent-0.23.0
 [0.22.0]: https://github.com/commonmark/commonmark-java/compare/commonmark-parent-0.21.0...commonmark-parent-0.22.0

commonmark/src/main/java/org/commonmark/internal/renderer/NodeRendererMap.java

@@ -13,6 +13,9 @@ public class NodeRendererMap {
     private final List<NodeRenderer> nodeRenderers = new ArrayList<>();
     private final Map<Class<? extends Node>, NodeRenderer> renderers = new HashMap<>(32);
 
+    /**
+     * Set the renderer for each {@link NodeRenderer#getNodeTypes()}, unless there was already a renderer set (first wins).
+     */
     public void add(NodeRenderer nodeRenderer) {
         nodeRenderers.add(nodeRenderer);
         for (var nodeType : nodeRenderer.getNodeTypes()) {

commonmark/src/main/java/org/commonmark/renderer/markdown/MarkdownRenderer.java

@@ -136,12 +136,10 @@ private RendererContext(MarkdownWriter writer) {
             }
             additionalTextEscapes = Collections.unmodifiableSet(escapes);
 
-            // The first node renderer for a node type "wins".
-            for (int i = nodeRendererFactories.size() - 1; i >= 0; i--) {
-                MarkdownNodeRendererFactory nodeRendererFactory = nodeRendererFactories.get(i);
+            for (var factory : nodeRendererFactories) {
                 // Pass in this as context here, which uses the fields set above
-                NodeRenderer nodeRenderer = nodeRendererFactory.create(this);
-                nodeRendererMap.add(nodeRenderer);
+                var renderer = factory.create(this);
+                nodeRendererMap.add(renderer);
             }
         }
 

commonmark/src/test/java/org/commonmark/renderer/markdown/MarkdownRendererTest.java

@@ -2,8 +2,14 @@
 
 import org.commonmark.node.*;
 import org.commonmark.parser.Parser;
+import org.commonmark.renderer.NodeRenderer;
+import org.commonmark.renderer.html.HtmlNodeRendererContext;
+import org.commonmark.renderer.html.HtmlNodeRendererFactory;
+import org.commonmark.renderer.html.HtmlRenderer;
 import org.junit.Test;
 
+import java.util.Set;
+
 import static org.commonmark.testutil.Asserts.assertRendering;
 import static org.junit.Assert.assertEquals;
 
@@ -300,6 +306,35 @@ public void testSoftLineBreaks() {
         assertRoundTrip("foo\nbar\n");
     }
 
+    @Test
+    public void overrideNodeRender() {
+        var nodeRendererFactory = new MarkdownNodeRendererFactory() {
+            @Override
+            public NodeRenderer create(MarkdownNodeRendererContext context) {
+                return new NodeRenderer() {
+                    @Override
+                    public Set<Class<? extends Node>> getNodeTypes() {
+                        return Set.of(Heading.class);
+                    }
+
+                    @Override
+                    public void render(Node node) {
+                        context.getWriter().raw("# Custom heading");
+                    }
+                };
+            }
+
+            @Override
+            public Set<Character> getSpecialCharacters() {
+                return Set.of();
+            }
+        };
+
+        MarkdownRenderer renderer = MarkdownRenderer.builder().nodeRendererFactory(nodeRendererFactory).build();
+        String rendered = renderer.render(parse("# Hello"));
+        assertEquals("# Custom heading\n", rendered);
+    }
+
     private void assertRoundTrip(String input) {
         String rendered = parseAndRender(input);
         assertEquals(input, rendered);