From ab0aaadd64f243bbe155377557dc72f209dd2dd7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Fournier?= <clement.fournier76@gmail.com>
Date: Fri, 7 Aug 2020 02:58:27 +0200
Subject: [PATCH] Fix descendantOrSelf on leaf

With a leaf node it used to return empty
---
 .../pmd/lang/ast/internal/SingletonNodeStream.java       | 9 ++++++++-
 .../sourceforge/pmd/lang/ast/internal/StreamImpl.java    | 4 ++--
 .../pmd/lang/ast/internal/NodeStreamTest.java            | 1 +
 3 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/internal/SingletonNodeStream.java b/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/internal/SingletonNodeStream.java
index efd5978dff..038a44e6b0 100644
--- a/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/internal/SingletonNodeStream.java
+++ b/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/internal/SingletonNodeStream.java
@@ -19,6 +19,7 @@ import net.sourceforge.pmd.internal.util.AssertionUtil;
 import net.sourceforge.pmd.internal.util.IteratorUtil;
 import net.sourceforge.pmd.lang.ast.Node;
 import net.sourceforge.pmd.lang.ast.NodeStream;
+import net.sourceforge.pmd.lang.ast.NodeStream.DescendantNodeStream;
 
 /**
  * Optimised node stream implementation for a single element. Streams
@@ -32,11 +33,12 @@ import net.sourceforge.pmd.lang.ast.NodeStream;
  * <p>This ensures that short pipelines like {@code node.descendants().first()}
  * are as efficient as the pre 7.0.0 methods.
  */
-final class SingletonNodeStream<T extends Node> extends IteratorBasedNStream<T> {
+final class SingletonNodeStream<T extends Node> extends IteratorBasedNStream<T> implements DescendantNodeStream<T> {
 
     private final T node;
 
     SingletonNodeStream(@NonNull T node) {
+        assert node != null : "null node!";
         this.node = node;
     }
 
@@ -207,4 +209,9 @@ final class SingletonNodeStream<T extends Node> extends IteratorBasedNStream<T>
     public NodeStream<Node> precedingSiblings() {
         return StreamImpl.precedingSiblings(node);
     }
+
+    @Override
+    public DescendantNodeStream<T> crossFindBoundaries(boolean cross) {
+        return this; // doesn't mean anything
+    }
 }
diff --git a/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/internal/StreamImpl.java b/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/internal/StreamImpl.java
index edac7e1b1e..c70239ed17 100644
--- a/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/internal/StreamImpl.java
+++ b/pmd-core/src/main/java/net/sourceforge/pmd/lang/ast/internal/StreamImpl.java
@@ -38,7 +38,7 @@ public final class StreamImpl {
         // utility class
     }
 
-    public static <T extends Node> NodeStream<T> singleton(@NonNull T node) {
+    public static <T extends Node> DescendantNodeStream<T> singleton(@NonNull T node) {
         return new SingletonNodeStream<>(node);
     }
 
@@ -88,7 +88,7 @@ public final class StreamImpl {
     }
 
     public static DescendantNodeStream<Node> descendantsOrSelf(@NonNull Node node) {
-        return node.getNumChildren() == 0 ? empty() : new DescendantOrSelfStream(node, TreeWalker.DEFAULT);
+        return node.getNumChildren() == 0 ? singleton(node) : new DescendantOrSelfStream(node, TreeWalker.DEFAULT);
     }
 
     public static NodeStream<Node> followingSiblings(@NonNull Node node) {
diff --git a/pmd-core/src/test/java/net/sourceforge/pmd/lang/ast/internal/NodeStreamTest.java b/pmd-core/src/test/java/net/sourceforge/pmd/lang/ast/internal/NodeStreamTest.java
index 9c4b738912..0bc4b03a1c 100644
--- a/pmd-core/src/test/java/net/sourceforge/pmd/lang/ast/internal/NodeStreamTest.java
+++ b/pmd-core/src/test/java/net/sourceforge/pmd/lang/ast/internal/NodeStreamTest.java
@@ -124,6 +124,7 @@ public class NodeStreamTest {
     public void testDescendantOrSelfStream() {
         assertThat(pathsOf(tree1.descendantsOrSelf()), contains("", "0", "00", "01", "010", "011", "0110", "012", "013", "1"));
         assertThat(pathsOf(NodeStream.of(tree1).descendantsOrSelf()), contains("", "0", "00", "01", "010", "011", "0110", "012", "013", "1"));
+        assertThat(pathsOf(followPath(tree1, "0110").descendantsOrSelf()), contains("0110")); // with a leaf node
     }
 
     @Test