Fix rendering anchor ref IDs (heading IDs) (#565)

flexmark-ext-attributes/src/main/java/com/vladsch/flexmark/ext/attributes/internal/AttributesAttributeProvider.java

@@ -58,7 +58,9 @@ public void setAttributes(@NotNull Node node, @NotNull AttributablePart part, @N
                                 attributes.addValue(CLASS_ATTR, attributeNode.getValue());
                             } else if (attributeNode.isId()) {
                                 if (node instanceof AnchorRefTarget) {
-                                    // was already provided via setAnchorRefId
+                                    // was already provided via setAnchorRefId, we only have to read it
+                                    attributes.remove(Attribute.ID_ATTR);
+                                    attributes.addValue(Attribute.ID_ATTR, ((AnchorRefTarget) node).getAnchorRefId());
                                 } else {
                                     attributes.remove(Attribute.ID_ATTR);
                                     attributes.addValue(Attribute.ID_ATTR, attributeNode.getValue());

flexmark-ext-attributes/src/test/java/com/vladsch/flexmark/ext/attributes/HtmlRendererHeadingIdsTest.java

@@ -0,0 +1,80 @@
+package com.vladsch.flexmark.ext.attributes;
+
+import com.vladsch.flexmark.ast.Heading;
+import com.vladsch.flexmark.ast.Text;
+import com.vladsch.flexmark.html.HtmlRenderer;
+import com.vladsch.flexmark.parser.Parser;
+import com.vladsch.flexmark.util.ast.Node;
+import com.vladsch.flexmark.util.data.MutableDataSet;
+import org.junit.Test;
+
+import java.io.IOException;
+import java.util.Arrays;
+
+import static org.junit.Assert.*;
+
+public class HtmlRendererHeadingIdsTest {
+
+    @Test
+    public void parserShouldReadHeadingIdsFromMarkdown() throws IOException {
+        String title = "Heading with ID";
+        String id = "heading-id-1";
+        String markdownSource = "# " + title + " {#" + id + "}";
+        Node parsed = parse(markdownSource);
+
+        assertTrue(parsed.hasChildren());
+        Node heading = parsed.getFirstChild();
+        assertEquals(Heading.class, heading.getClass());
+        assertEquals(id, ((Heading) heading).getAnchorRefId());
+        assertTrue(((Heading) heading).isExplicitAnchorRefId());
+        assertTrue(heading.hasChildren());
+
+        Node headingText = heading.getFirstChild();
+        assertEquals(Text.class, headingText.getClass());
+        assertEquals(title, headingText.getChars().toString());
+
+        Node headingAttributes = headingText.getNext();
+        assertEquals(AttributesNode.class, headingAttributes.getClass());
+        assertEquals("#" + id, ((AttributesNode) headingAttributes).getText().toString());
+        assertTrue(headingAttributes.hasChildren());
+
+        Node headingId = headingAttributes.getFirstChild();
+        assertEquals(AttributeNode.class, headingId.getClass());
+        assertEquals(id, ((AttributeNode) headingId).getValue().toString());
+        assertFalse(headingId.hasChildren());
+    }
+
+    @Test
+    public void headingWithoutIdShouldNotGetGeneratedIdInHtml() {
+        String markdownSource = "# Heading without ID";
+        Node parsed = parse(markdownSource);
+        String rendered = createRendererNotGeneratingButRenderingIds().render(parsed);
+        assertEquals("<h1>Heading without ID</h1>\n", rendered);
+    }
+    @Test
+    public void headingWithExplicitlySetIdShouldGetThatIdInHtml() {
+        String markdownSource = "# Heading with ID {#heading-id-1}";
+        Node parsed = parse(markdownSource);
+        String rendered = createRendererNotGeneratingButRenderingIds().render(parsed);
+        assertEquals("<h1 id=\"heading-id-1\">Heading with ID</h1>\n", rendered);
+    }
+
+    private static HtmlRenderer createRendererNotGeneratingButRenderingIds() {
+        return HtmlRenderer.builder(getSettings()).build();
+    }
+
+    private static Node parse(String source) {
+        return Parser.builder(getSettings()).build().parse(source);
+    }
+
+    private static MutableDataSet getSettings() {
+        MutableDataSet options = new MutableDataSet();
+        options.set(Parser.BLANK_LINES_IN_AST, false);
+        options.set(HtmlRenderer.RENDER_HEADER_ID, true);
+        options.set(HtmlRenderer.GENERATE_HEADER_ID, false);
+        options.set(Parser.EXTENSIONS, Arrays.asList(
+                AttributesExtension.create()));
+        return options;
+    }
+
+}