From 55951c3025cf088487fdd91af800b4e92ae8f892 Mon Sep 17 00:00:00 2001
From: rdb <git@rdb.name>
Date: Tue, 2 Jun 2020 20:23:38 +0200
Subject: [PATCH] pgraph: fix has_tags() after clearing Python tags

Fixes #936
---
 panda/src/pgraph/pandaNode_ext.cxx |  6 ++++++
 tests/pgraph/test_nodepath.py      | 29 +++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+)

diff --git a/panda/src/pgraph/pandaNode_ext.cxx b/panda/src/pgraph/pandaNode_ext.cxx
index bc6427b1d0..d4071ff4c6 100644
--- a/panda/src/pgraph/pandaNode_ext.cxx
+++ b/panda/src/pgraph/pandaNode_ext.cxx
@@ -165,6 +165,12 @@ clear_python_tag(PyObject *key) {
   if (PyDict_GetItem(dict, key) != nullptr) {
     PyDict_DelItem(dict, key);
   }
+
+  if (PyDict_Size(dict) == 0 && Py_REFCNT(dict) == 1) {
+    // This was the last tag, and do_get_python_tags() made sure we have a
+    // unique reference to the tags, so clear the tag object.
+    _this->_python_tag_data.clear();
+  }
 }
 
 /**
diff --git a/tests/pgraph/test_nodepath.py b/tests/pgraph/test_nodepath.py
index 7dcbd2662b..43e43313e1 100644
--- a/tests/pgraph/test_nodepath.py
+++ b/tests/pgraph/test_nodepath.py
@@ -151,6 +151,35 @@ def test_nodepath_python_tags():
     assert rc1 == rc2
 
 
+def test_nodepath_clear_python_tag():
+    from panda3d.core import NodePath
+
+    path = NodePath("node")
+    assert not path.has_python_tag("a")
+    assert not path.has_python_tag("b")
+    assert not path.node().has_tags()
+
+    path.set_python_tag("a", "value")
+    assert path.has_python_tag("a")
+    assert not path.has_python_tag("b")
+    assert path.node().has_tags()
+
+    path.set_python_tag("b", "value")
+    assert path.has_python_tag("a")
+    assert path.has_python_tag("b")
+    assert path.node().has_tags()
+
+    path.clear_python_tag("a")
+    assert not path.has_python_tag("a")
+    assert path.has_python_tag("b")
+    assert path.node().has_tags()
+
+    path.clear_python_tag("b")
+    assert not path.has_python_tag("a")
+    assert not path.has_python_tag("b")
+    assert not path.node().has_tags()
+
+
 def test_nodepath_replace_texture():
     from panda3d.core import NodePath, Texture