Preserve literal ampersands in Markdown links and images

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

@@ -27,10 +27,10 @@ public class CoreMarkdownNodeRenderer extends AbstractVisitor implements NodeRen
     private final CharMatcher textEscapeInHeading;
     private final CharMatcher linkDestinationNeedsAngleBrackets =
             AsciiMatcher.builder().c(' ').c('(').c(')').c('<').c('>').c('\n').c('\\').build();
-    private final CharMatcher linkDestinationEscapeInAngleBrackets =
-            AsciiMatcher.builder().c('<').c('>').c('\n').c('\\').build();
+    private final CharMatcher linkDestinationEscape =
+            AsciiMatcher.builder().c('<').c('>').c('\n').c('\\').c('&').build();
     private final CharMatcher linkTitleEscapeInQuotes =
-            AsciiMatcher.builder().c('"').c('\n').c('\\').build();
+            AsciiMatcher.builder().c('"').c('\n').c('\\').c('&').build();
 
     private final Pattern orderedListMarkerPattern = Pattern.compile("^([0-9]{1,9})([.)])");
 
@@ -523,10 +523,10 @@ private void writeLinkLike(String title, String destination, Node node, String o
         writer.raw('(');
         if (contains(destination, linkDestinationNeedsAngleBrackets)) {
             writer.raw('<');
-            writer.text(destination, linkDestinationEscapeInAngleBrackets);
+            writer.text(destination, linkDestinationEscape);
             writer.raw('>');
         } else {
-            writer.raw(destination);
+            writer.text(destination, linkDestinationEscape);
         }
         if (title != null) {
             writer.raw(' ');

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

@@ -8,6 +8,8 @@
 import org.commonmark.parser.Parser;
 import org.commonmark.renderer.NodeRenderer;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
 
 public class MarkdownRendererTest {
 
@@ -297,6 +299,60 @@ public void testImages() {
         assertRoundTrip("![a](/uri \"foo \\\" bar\")\n");
     }
 
+    @ParameterizedTest
+    @ValueSource(
+            strings = {
+                "/url?value=©",
+                "/my uri?value=©",
+                "/url?value=A",
+                "/url?value=A",
+                "/url?a=1&b=2"
+            })
+    public void testLinkDestinationPreservesLiteralAmpersands(String destination) {
+        Link link = new Link(destination, null);
+        link.appendChild(new Text("link"));
+
+        Link reparsed = (Link) parse(render(link)).getFirstChild().getFirstChild();
+        assertThat(reparsed.getDestination()).isEqualTo(destination);
+    }
+
+    @ParameterizedTest
+    @ValueSource(
+            strings = {
+                "/url?value=©",
+                "/my uri?value=©",
+                "/url?value=A",
+                "/url?value=A",
+                "/url?a=1&b=2"
+            })
+    public void testImageDestinationPreservesLiteralAmpersands(String destination) {
+        Image image = new Image(destination, null);
+        image.appendChild(new Text("image"));
+
+        Image reparsed = (Image) parse(render(image)).getFirstChild().getFirstChild();
+        assertThat(reparsed.getDestination()).isEqualTo(destination);
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"literal ©", "literal A", "literal A", "bread & butter"})
+    public void testLinkTitlePreservesLiteralAmpersands(String title) {
+        Link link = new Link("/url", title);
+        link.appendChild(new Text("link"));
+
+        Link reparsed = (Link) parse(render(link)).getFirstChild().getFirstChild();
+        assertThat(reparsed.getTitle()).isEqualTo(title);
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"literal ©", "literal A", "literal A", "bread & butter"})
+    public void testImageTitlePreservesLiteralAmpersands(String title) {
+        Image image = new Image("/url", title);
+        image.appendChild(new Text("image"));
+
+        Image reparsed = (Image) parse(render(image)).getFirstChild().getFirstChild();
+        assertThat(reparsed.getTitle()).isEqualTo(title);
+    }
+
     @Test
     public void testHtmlInline() {
         assertRoundTrip("<del>*foo*</del>\n");