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bpo-30597: Show expected input in custom 'print' error message. (#2009)

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CuriousLearner authored and serhiy-storchaka committed Jun 20, 2017
1 parent 90e01e5 commit 3a7f03584ab75afbf5507970711c87042e423bb4
Showing with 76 additions and 3 deletions.
  1. +28 −0 Lib/test/test_print.py
  2. +3 −0 Misc/NEWS
  3. +45 −3 Objects/exceptions.c
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@@ -128,5 +128,33 @@ def flush(self):
raise RuntimeError
self.assertRaises(RuntimeError, print, 1, file=noflush(), flush=True)
class TestPy2MigrationHint(unittest.TestCase):
"""Test that correct hint is produced analogous to Python3 syntax,
if print statement is executed as in Python 2.
"""
def test_normal_string(self):
python2_print_str = 'print "Hello World"'
with self.assertRaises(SyntaxError) as context:
exec(python2_print_str)
self.assertIn('print("Hello World")', str(context.exception))
def test_string_with_soft_space(self):
python2_print_str = 'print "Hello World",'
with self.assertRaises(SyntaxError) as context:
exec(python2_print_str)
self.assertIn('print("Hello World", end=" ")', str(context.exception))
def test_string_with_excessive_whitespace(self):
python2_print_str = 'print "Hello World", '
with self.assertRaises(SyntaxError) as context:
exec(python2_print_str)
self.assertIn('print("Hello World", end=" ")', str(context.exception))
if __name__ == "__main__":
unittest.main()
View
@@ -10,6 +10,9 @@ What's New in Python 3.7.0 alpha 1?
Core and Builtins
-----------------
- bpo-30597: ``print`` now shows expected input in custom error message when
used as a Python 2 statement. Patch by Sanyam Khurana.
- bpo-30682: Removed a too-strict assertion that failed for certain f-strings,
such as eval("f'\\\n'") and eval("f'\\\r'").
View
@@ -2862,6 +2862,49 @@ _PyErr_TrySetFromCause(const char *format, ...)
* or minus, using the stream redirection syntax).
*/
// Static helper for setting legacy print error message
static int
_set_legacy_print_statement_msg(PySyntaxErrorObject *self, Py_ssize_t start)
{
PyObject *strip_sep_obj = PyUnicode_FromString(" \t\r\n");
if (strip_sep_obj == NULL)
return -1;
// PRINT_OFFSET is to remove `print ` word from the data.
const int PRINT_OFFSET = 6;
Py_ssize_t text_len = PyUnicode_GET_LENGTH(self->text);
PyObject *data = PyUnicode_Substring(self->text, PRINT_OFFSET, text_len);
if (data == NULL) {
Py_DECREF(strip_sep_obj);
return -1;
}
PyObject *new_data = _PyUnicode_XStrip(data, 2, strip_sep_obj);
Py_DECREF(data);
Py_DECREF(strip_sep_obj);
if (new_data == NULL) {
return -1;
}
// gets the modified text_len after stripping `print `
text_len = PyUnicode_GET_LENGTH(new_data);
const char *maybe_end_arg = "";
if (text_len > 0 && PyUnicode_READ_CHAR(new_data, text_len-1) == ',') {
maybe_end_arg = " end=\" \"";
}
PyObject *error_msg = PyUnicode_FromFormat(
"Missing parentheses in call to 'print'. Did you mean print(%U%s)?",
new_data, maybe_end_arg
);
Py_DECREF(new_data);
if (error_msg == NULL)
return -1;
Py_XSETREF(self->msg, error_msg);
return 1;
}
static int
_check_for_legacy_statements(PySyntaxErrorObject *self, Py_ssize_t start)
{
@@ -2897,9 +2940,8 @@ _check_for_legacy_statements(PySyntaxErrorObject *self, Py_ssize_t start)
}
if (PyUnicode_Tailmatch(self->text, print_prefix,
start, text_len, -1)) {
Py_XSETREF(self->msg,
PyUnicode_FromString("Missing parentheses in call to 'print'"));
return 1;
return _set_legacy_print_statement_msg(self, start);
}
/* Check for legacy exec statements */

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