fix(JavaDoc): Collapsed markdown comments with wrong suffixes

Not perfect at all, it should be able to rely on the commenter API instead.

GitOrigin-RevId: f41d181e9f27905bca1156912b7850f5a96ba943

java/java-psi-impl/src/com/intellij/codeInsight/folding/impl/JavaFoldingBuilderBase.java

@@ -198,7 +198,19 @@ public abstract class JavaFoldingBuilderBase extends CustomFoldingBuilder implem
     final FoldingDescriptor commentDescriptor = CommentFoldingUtil.getCommentDescriptor(comment, document, processedComments,
                                                                                         element -> isCustomRegionElement(element),
                                                                                         isCollapseCommentByDefault(comment));
-    if (commentDescriptor != null) list.add(commentDescriptor);
+    if (commentDescriptor != null) {
+      if (comment instanceof PsiDocComment && ((PsiDocComment)comment).isMarkdownComment()) {
+        // Hack: Markdown comments aren't documented in the Commenter for the Java language
+        // To avoid the `/** */` tokens, we remove them
+        String placeHolderText = commentDescriptor.getPlaceholderText();
+        if (placeHolderText != null) {
+          placeHolderText = StringUtil.trimEnd(StringUtil.trimStart(placeHolderText, "/**"), "*/");
+          commentDescriptor.setPlaceholderText(placeHolderText);
+        }
+      }
+
+      list.add(commentDescriptor);
+    }
   }
 
   private static void addMethodGenericParametersFolding(@NotNull List<? super FoldingDescriptor> list,

java/java-tests/testData/codeInsight/folding/JavadocMarkdownComments.java

@@ -0,0 +1,71 @@
+<fold text='/// outer class javadoc ...'>/// outer class javadoc
+ /// javadoc body</fold>
+
+class Test {
+
+  <fold text='/// method javadoc ...'>/// method javadoc
+   /// javadoc body
+   ///
+   /// @param i</fold>
+
+  void foo(int i) <fold text='{...}'>{
+    <fold text='/// method var javadoc ...'>/// method var javadoc
+     /// javadoc body</fold>
+
+    int j = i;
+  }</fold>
+
+  <fold text='/// first line ...'>/// first line
+   /// second line</fold>
+
+  void illFormedJavaDocMultilines() <fold text='{}'>{
+  }</fold>
+
+  <fold text='/// first line ...'>/// first line
+   ///
+   ///</fold>
+
+  void javaDocWithTextOnlyOnFirstLine() <fold text='{}'>{
+
+  }</fold>
+
+  <fold text='/// second line ...'>/// second line
+   ///</fold>
+
+  void javaDocWithTextOnlyOnSecondLine() <fold text='{}'>{
+
+  }</fold>
+
+  <fold text='///  '>/// </fold>
+
+  void emptyJavadoc() <fold text='{}'>{
+
+  }</fold>
+
+  <fold text='/// dangling javadoc ...'>/// dangling javadoc
+   /// javadoc body</fold>
+
+
+  <fold text='/// inner class javadoc ...'>/// inner class javadoc
+   /// javadoc body</fold>
+
+  class Inner <fold text='{...}'>{
+
+    <fold text='/// javadoc for method in inner class ...'>/// javadoc for method in inner class
+     /// javadoc body</fold>
+
+    void foo() <fold text='{...}'>{
+      <fold text='/// javadoc for class in method ...'>/// javadoc for class in method
+       /// javadoc body</fold>
+
+      class MethodInner <fold text='{...}'>{
+
+        <fold text='/// javadoc for method inside class defined in method ...'>/// javadoc for method inside class defined in method
+         /// javadoc body</fold>
+
+        void bar() <fold text='{}'>{
+        }</fold>
+      }</fold>
+    }</fold>
+  }</fold>
+}

java/java-tests/testSrc/com/intellij/openapi/editor/impl/JavaFoldingTest.java

@@ -49,6 +49,8 @@ public class JavaFoldingTest extends JavaFoldingTestCase {
 
   public void testJavadocComments() { doTest(); }
 
+  public void testJavadocMarkdownComments() { doTest(); }
+
   public void testEditingImports() {
     configure("""
                 import java.util.List;