Thanks to visit codestin.com
Credit goes to github.com

Skip to content

gh-132661: Disallow Template/str concatenation after PEP 750 spec update #135996

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Draft
wants to merge 2 commits into
base: main
Choose a base branch
from
+32 −149
Draft

gh-132661: Disallow Template/str concatenation after PEP 750 spec update #135996

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
5d5e187
Disallow explicit concat between Template and str
davepeck Jun 26, 2025
1cc778f
First pass at removing implicit Template/str concat
davepeck Jun 26, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 0 additions & 7 deletions Lib/test/test_ast/test_ast.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -999,13 +999,6 @@ def test_tstring(self):
self.assertIsInstance(tree.body[0].value.values[0], ast.Constant)
self.assertIsInstance(tree.body[0].value.values[1], ast.Interpolation)

# Test AST for implicit concat of t-string with f-string
tree = ast.parse('t"Hello {name}" f"{name}"')
self.assertIsInstance(tree.body[0].value, ast.TemplateStr)
self.assertIsInstance(tree.body[0].value.values[0], ast.Constant)
self.assertIsInstance(tree.body[0].value.values[1], ast.Interpolation)
self.assertIsInstance(tree.body[0].value.values[2], ast.FormattedValue)


class CopyTests(unittest.TestCase):
"""Test copying and pickling AST nodes."""
Expand Down
61 changes: 17 additions & 44 deletions Lib/test/test_tstring.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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):
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Will it make sense to check error message here?

_ = t1 + ", world"

# Test template + template with interpolation
name = "Python"
Expand All @@ -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
Expand Down Expand Up @@ -241,45 +239,20 @@ def test_literal_concatenation(self):
self.assertTStringEqual(t, ("Hello, ", ""), [(name, "name")])
self.assertEqual(fstring(t), "Hello, Python")

# Test concatenation with string literal
name = "Python"
t = t"Hello, {name}" "and welcome!"
self.assertTStringEqual(
t, ("Hello, ", "and welcome!"), [(name, "name")]
)
self.assertEqual(fstring(t), "Hello, Pythonand welcome!")

# Test concatenation with Unicode literal
name = "Python"
t = t"Hello, {name}" u"and welcome!"
self.assertTStringEqual(
t, ("Hello, ", "and welcome!"), [(name, "name")]
)
self.assertEqual(fstring(t), "Hello, Pythonand welcome!")

# Test concatenation with f-string literal
tab = '\t'
t = t"Tab: {tab}. " f"f-tab: {tab}."
self.assertTStringEqual(t, ("Tab: ", ". f-tab: \t."), [(tab, "tab")])
self.assertEqual(fstring(t), "Tab: \t. f-tab: \t.")

# Test concatenation with raw string literal
tab = '\t'
t = t"Tab: {tab}. " r"Raw tab: \t."
self.assertTStringEqual(
t, ("Tab: ", r". Raw tab: \t."), [(tab, "tab")]
)
self.assertEqual(fstring(t), "Tab: \t. Raw tab: \\t.")

# Test concatenation with raw f-string literal
tab = '\t'
t = t"Tab: {tab}. " rf"f-tab: {tab}. Raw tab: \t."
self.assertTStringEqual(
t, ("Tab: ", ". f-tab: \t. Raw tab: \\t."), [(tab, "tab")]
)
self.assertEqual(fstring(t), "Tab: \t. f-tab: \t. Raw tab: \\t.")

# Test disallowed mix of t-string and string
what = 't'
expected_msg = 'cannot mix str and Template literals'
for case in (
"t'{what}-string literal' 'str literal'",
"t'{what}-string literal' u'unicode literal'",
"t'{what}-string literal' f'f-string literal'",
"t'{what}-string literal' r'raw string literal'",
"t'{what}-string literal' rf'raw f-string literal'",
):
with self.assertRaisesRegex(SyntaxError, expected_msg):
eval(case)

# Test disallowed mix of t-string and bytes
expected_msg = 'cannot mix bytes and nonbytes literals'
for case in (
"t'{what}-string literal' b'bytes literal'",
Expand Down
4 changes: 0 additions & 4 deletions Lib/test/test_unparse.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -206,10 +206,6 @@ def test_tstrings(self):
self.check_ast_roundtrip("t'foo'")
self.check_ast_roundtrip("t'foo {bar}'")
self.check_ast_roundtrip("t'foo {bar!s:.2f}'")
self.check_ast_roundtrip("t'foo {bar}' f'{bar}'")
self.check_ast_roundtrip("f'{bar}' t'foo {bar}'")
self.check_ast_roundtrip("t'foo {bar}' fr'\\hello {bar}'")
self.check_ast_roundtrip("t'foo {bar}' u'bar'")

def test_strings(self):
self.check_ast_roundtrip("u'foo'")
Expand Down
88 changes: 5 additions & 83 deletions Objects/templateobject.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand Down Expand Up @@ -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;
}
}

Expand Down
15 changes: 4 additions & 11 deletions Objects/unicodeobject.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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,
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

You can use %T to format object's type.

"can only concatenate str (not \"%.200s\") to str",
Py_TYPE(right)->tp_name);
return NULL;
}

/* Shortcuts */
Expand Down
6 changes: 6 additions & 0 deletions Parser/action_helpers.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1887,6 +1887,11 @@ _PyPegen_concatenate_strings(Parser *p, asdl_expr_seq *strings,
return NULL;
}

if ((unicode_string_found || f_string_found) && t_string_found) {
RAISE_SYNTAX_ERROR("cannot mix str and Template literals");
return NULL;
}

// If it's only bytes or only unicode string, do a simple concat
if (!f_string_found && !t_string_found) {
if (len == 1) {
Expand All @@ -1902,6 +1907,7 @@ _PyPegen_concatenate_strings(Parser *p, asdl_expr_seq *strings,
}
}


Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

unrelated change :)

if (t_string_found) {
return _build_concatenated_template_str(p, strings, lineno,
col_offset, end_lineno, end_col_offset, arena);
Expand Down
Loading