Disallow explicit concat between Template and str

python · davepeck · Ju 8000 n 26, 2025 · Jun 26, 2025 · Jun 30, 2025 · Jul 8, 2025
commit 5d5e187ba8015a0db94163e6f845aee4cfbd55cd
@@ -161,9 +161,8 @@ def test_template_concatenation(self):
 
         # Test template + string
         t1 = t"Hello"
-        combined = t1 + ", world"
-        self.assertTStringEqual(combined, ("Hello, world",), ())
-        self.assertEqual(fstring(combined), "Hello, world")
+        with self.assertRaises(TypeError):
+            _ = t1 + ", world"
 
         # Test template + template with interpolation
         name = "Python"
@@ -174,9 +173,8 @@ def test_template_concatenation(self):
         self.assertEqual(fstring(combined), "Hello, Python")
 
         # Test string + template
-        t = "Hello, " + t"{name}"
-        self.assertTStringEqual(t, ("Hello, ", ""), [(name, "name")])
-        self.assertEqual(fstring(t), "Hello, Python")
+        with self.assertRaises(TypeError):
+            _ = "Hello, " + t"{name}"
 
     def test_nested_templates(self):
         # Test a template inside another template expression

@@ -245,54 +245,6 @@ template_iter(PyObject *op)
     return (PyObject *)iter;
 }
 
-static PyObject *
-template_strings_append_str(PyObject *strings, PyObject *str)
-{
-    Py_ssize_t stringslen = PyTuple_GET_SIZE(strings);
-    PyObject *string = PyTuple_GET_ITEM(strings, stringslen - 1);
-    PyObject *concat = PyUnicode_Concat(string, str);
-    if (concat == NULL) {
-        return NULL;
-    }
-
-    PyObject *newstrings = PyTuple_New(stringslen);
-    if (newstrings == NULL) {
-        Py_DECREF(concat);
-        return NULL;
-    }
-
-    for (Py_ssize_t i = 0; i < stringslen - 1; i++) {
-        PyTuple_SET_ITEM(newstrings, i, Py_NewRef(PyTuple_GET_ITEM(strings, i)));
-    }
-    PyTuple_SET_ITEM(newstrings, stringslen - 1, concat);
-
-    return newstrings;
-}
-
-static PyObject *
-template_strings_prepend_str(PyObject *strings, PyObject *str)
-{
-    Py_ssize_t stringslen = PyTuple_GET_SIZE(strings);
-    PyObject *string = PyTuple_GET_ITEM(strings, 0);
-    PyObject *concat = PyUnicode_Concat(str, string);
-    if (concat == NULL) {
-        return NULL;
-    }
-
-    PyObject *newstrings = PyTuple_New(stringslen);
-    if (newstrings == NULL) {
-        Py_DECREF(concat);
        return NULL;
-    }
-
-    PyTuple_SET_ITEM(newstrings, 0, concat);
-    for (Py_ssize_t i = 1; i < stringslen; i++) {
-        PyTuple_SET_ITEM(newstrings, i, Py_NewRef(PyTuple_GET_ITEM(strings, i)));
-    }
-
-    return newstrings;
-}
-
 static PyObject *
 template_strings_concat(PyObject *left, PyObject *right)
 {
@@ -344,46 +296,16 @@ template_concat_templates(templateobject *self, templateobject *other)
     return newtemplate;
 }
 
-static PyObject *
-template_concat_template_str(templateobject *self, PyObject *other)
-{
-    PyObject *newstrings = template_strings_append_str(self->strings, other);
-    if (newstrings == NULL) {
-        return NULL;
-    }
-
-    PyObject *newtemplate = _PyTemplate_Build(newstrings, self->interpolations);
-    Py_DECREF(newstrings);
-    return newtemplate;
-}
-
-static PyObject *
-template_concat_str_template(templateobject *self, PyObject *other)
-{
-    PyObject *newstrings = template_strings_prepend_str(self->strings, other);
-    if (newstrings == NULL) {
-        return NULL;
-    }
-
-    PyObject *newtemplate = _PyTemplate_Build(newstrings, self->interpolations);
-    Py_DECREF(newstrings);
-    return newtemplate;
-}
-
 PyObject *
 _PyTemplate_Concat(PyObject *self, PyObject *other)
 {
     if (_PyTemplate_CheckExact(self) && _PyTemplate_CheckExact(other)) {
         return template_concat_templates((templateobject *) self, (templateobject *) other);
-    }
-    else if ((_PyTemplate_CheckExact(self)) && PyUnicode_Check(other)) {
-        return template_concat_template_str((templateobject *) self, other);
-    }
-    else if (PyUnicode_Check(self) && (_PyTemplate_CheckExact(other))) {
-        return template_concat_str_template((templateobject *) other, self);
-    }
-    else {
-        Py_RETURN_NOTIMPLEMENTED;
+    } else {
+        PyErr_Format(PyExc_TypeError,
+            "can only concatenate Template (not \"%.200s\") to Template",
+            Py_TYPE(other)->tp_name);
+        return NULL;
     }
 }
 

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
@@ -56,7 +56,6 @@ OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 #include "pycore_pyhash.h"        // _Py_HashSecret_t
 #include "pycore_pylifecycle.h"   // _Py_SetFileSystemEncoding()
 #include "pycore_pystate.h"       // _PyInterpreterState_GET()
-#include "pycore_template.h"      // _PyTemplate_Concat()
 #include "pycore_tuple.h"         // _PyTuple_FromArray()
 #include "pycore_ucnhash.h"       // _PyUnicode_Name_CAPI
 #include "pycore_unicodeobject.h" // struct _Py_unicode_state
@@ -11610,16 +11609,10 @@ PyUnicode_Concat(PyObject *left, PyObject *right)
         return NULL;
 
     if (!PyUnicode_Check(right)) {
-        if (_PyTemplate_CheckExact(right)) {
-            // str + tstring is implemented in the tstring type
-            return _PyTemplate_Concat(left, right);
-        }
-        else {
-            PyErr_Format(PyExc_TypeError,
-                "can only concatenate str (not \"%.200s\") to str",
-                Py_TYPE(right)->tp_name);
-            return NULL;
-        }
+        PyErr_Format(PyExc_TypeError,
+            "can only concatenate str (not \"%.200s\") to str",
+            Py_TYPE(right)->tp_name);
+        return NULL;
     }
 
     /* Shortcuts */