Fix copy() with predicate

nutree/node.py

@@ -906,7 +906,14 @@ def _visit(other: Node) -> None:
                 parent_stack.append((False, n))
 
                 res = call_predicate(predicate, n)
-                if isinstance(res, SkipBranch):
+
+                if res is None or res is False:  # Add only if has a `true` descendant
+                    _visit(n)
+                elif res is True:  # Add this node (and also check children)
+                    p = _create_parents()
+                    # p.add_child(n)
+                    _visit(n)
+                elif isinstance(res, SkipBranch):
                     if res.and_self is False:
                         # Add the node itself if user explicitly returned
                         # `SkipBranch(and_self=False)`
@@ -918,12 +925,8 @@ def _visit(other: Node) -> None:
                     # Unconditionally copy whole branch: no need to visit children
                     p = _create_parents()
                     p._add_from(n)
-                elif res in (None, False):  # Add only if has a `true` descendant
-                    _visit(n)
-                elif res is True:  # Add this node (and also check children)
-                    p = _create_parents()
-                    p.add_child(n)
-                    _visit(n)
+                else:
+                    raise ValueError(f"Invalid predicate return value: {res}")
 
                 parent_stack.pop()
             return
@@ -958,7 +961,7 @@ def _visit(parent: Node) -> bool:
 
             for n in parent.children:
                 res = call_predicate(predicate, n)
-                if res in (None, False):  # Keep only if has a `true` descendant
+                if res is None or res is False:  # Keep only if has a `true` descendant
                     if _visit(n):
                         must_keep = True
                     else:

tests/fixture.py

@@ -253,6 +253,9 @@ def _check_content(
         else:
             style = "ascii32"
 
+    if isinstance(tree, Tree):
+        assert tree._self_check()
+
     s1 = indent(canonical_repr(tree, repr=repr, style=style), "    ")
     s2 = indent(canonical_repr(expect_ascii, repr=repr, style=style), "    ")
     if ignore_tree_name:
@@ -281,6 +284,9 @@ def check_content(
 
 
 def trees_equal(tree_1, tree_2, ignore_tree_name=True) -> bool:
+    assert tree_1 is not tree_2
+    if not tree_1 or not tree_2 or (len(tree_1) != len(tree_2)):
+        return False
     return check_content(tree_1, tree_2, ignore_tree_name=ignore_tree_name)
 
 

tests/test_core.py

@@ -1125,7 +1125,6 @@ def test_tree_copy(self):
                `- a12
             """,
         )
-        assert subtree._self_check()
 
         subtree = tree["A"].copy(add_self=False)
         assert fixture.check_content(
@@ -1138,7 +1137,26 @@ def test_tree_copy(self):
             `- a2
             """,
         )
-        assert subtree._self_check()
+
+    def test_node_copy_predicate(self):
+        tree = fixture.create_tree()
+
+        tree_2 = tree.copy()
+        assert fixture.trees_equal(tree, tree_2)
+
+        tree_3 = tree.copy(predicate=lambda n: "2" not in n.name.lower())
+        assert fixture.check_content(
+            tree_3,
+            """
+            Tree<'fixture'>
+            ├── A
+            │   ╰── a1
+            │       ╰── a11
+            ╰── B
+                ╰── b1
+                    ╰── b11
+            """,
+        )
 
     def test_node_copy_to(self):
         tree_1 = fixture.create_tree()
@@ -1278,17 +1296,14 @@ def pred(node):
 
         tree_2 = tree.filtered(predicate=pred)
 
-        assert tree_2._self_check()
         assert fixture.check_content(
             tree_2,
             """
             Tree<*>
             ╰── A
                 ├── a1
                 │   ╰── a12
-                │       ╰── a12
                 ╰── a2
-                    ╰── a2
             """,
         )
 
@@ -1299,14 +1314,12 @@ def pred(node):
 
         tree_2 = tree.filtered(predicate=pred)
 
-        assert tree_2._self_check()
         assert fixture.check_content(
             tree_2,
             """
             Tree<*>
             ╰── A
                 ╰── a2
-                    ╰── a2
             """,
         )