Fix debug assert in test signals/bug_189.py

Do not use the %S-formatting directive when an error is already set,
since that will invoke str() and thus cause an error.

Amends d7aa15abe25bd71ea19180743ce9b41e0b788520.

Task-number: PYSIDE-1275
Change-Id: I1125ca254efdeeb3652d6171d71f3e22fb686a7a
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

1 files changed, 7 insertions, 2 deletions

diff --git a/sources/pyside6/libpyside/pysidesignal.cpp b/sources/pyside6/libpyside/pysidesignal.cpp
index ecfb92d15..c93cbadfb 100644
--- a/sources/pyside6/libpyside/pysidesignal.cpp
+++ b/sources/pyside6/libpyside/pysidesignal.cpp
@@ -663,8 +663,13 @@ static PyObject *signalInstanceGetItem(PyObject *self, PyObject *key)
 
 static inline void warnDisconnectFailed(PyObject *aSlot, const QByteArray &signature)
 {
-    PyErr_WarnFormat(PyExc_RuntimeError, 0, "Failed to disconnect (%S) from signal \"%s\".",
-                     aSlot, signature.constData());
+    if (PyErr_Occurred() != nullptr) { // avoid "%S" invoking str() when an error is set.
+        PyErr_WarnFormat(PyExc_RuntimeError, 0, "Failed to disconnect (%s) from signal \"%s\".",
+                         Py_TYPE(aSlot)->tp_name, signature.constData());
+    } else {
+        PyErr_WarnFormat(PyExc_RuntimeError, 0, "Failed to disconnect (%S) from signal \"%s\".",
+                         aSlot, signature.constData());
+    }
 }
 
 static PyObject *signalInstanceDisconnect(PyObject *self, PyObject *args)