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Merged
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Jul 27, 2021
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bpo-34013: Move the Python 2 hints from the exception constructor to the parser #27392

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7 changes: 4 additions & 3 deletions Grammar/python.gram
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Expand Up @@ -848,9 +848,10 @@ expression_without_invalid[expr_ty]:
| disjunction
| lambdef
invalid_legacy_expression:
| a=NAME b=expression_without_invalid {
_PyPegen_check_legacy_stmt(p, a) ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b, "Missing parentheses in call to '%U'.", a->v.Name.id) : NULL}

| a=NAME b=star_expressions {
_PyPegen_check_legacy_stmt(p, a) ? RAISE_SYNTAX_ERROR_KNOWN_RANGE(a, b,
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Where do the carets for this end up? If they're at the end of the expression, LGTM.

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>>> print a+b, c+d, f()
  File "<stdin>", line 1
    print a+b, c+d, f()
    ^^^^^^^^^^^^^^^^^^^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print(...)?

>>> 3,4 , [print 3+4, 6+7, 8], 34
  File "<stdin>", line 1
    3,4 , [print 3+4, 6+7, 8], 34
           ^^^^^^^^^^^^^^^^^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print(...)?

>>> print {3+4, 6+7, 8}, 45, 6
  File "<stdin>", line 1
    print {3+4, 6+7, 8}, 45, 6
    ^^^^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print(...)?

>>> (print {3+4, 6+7, 8}, 45, 6), 5
  File "<stdin>", line 1
    (print {3+4, 6+7, 8}, 45, 6), 5
     ^^^^^^^^^^^^^^^^^^^^^^^^^^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print(...)?

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perfect 👌

"Missing parentheses in call to '%U'. Did you mean %U(...)?", a->v.Name.id, a->v.Name.id) : NULL}

invalid_expression:
| invalid_legacy_expression
# !(NAME STRING) is not matched so we don't show this error with some invalid string prefixes like: kf"dsfsdf"
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12 changes: 5 additions & 7 deletions Lib/test/test_exceptions.py
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Expand Up @@ -168,21 +168,19 @@ def ckmsg(src, msg, exception=SyntaxError):
self.fail("failed to get expected SyntaxError")

s = '''print "old style"'''
ckmsg(s, "Missing parentheses in call to 'print'. "
"Did you mean print(\"old style\")?")
ckmsg(s, "Missing parentheses in call to 'print'. Did you mean print(...)?")

s = '''print "old style",'''
ckmsg(s, "Missing parentheses in call to 'print'. "
"Did you mean print(\"old style\", end=\" \")?")
ckmsg(s, "Missing parentheses in call to 'print'. Did you mean print(...)?")

s = 'print f(a+b,c)'
ckmsg(s, "Missing parentheses in call to 'print'.")
ckmsg(s, "Missing parentheses in call to 'print'. Did you mean print(...)?")

s = '''exec "old style"'''
ckmsg(s, "Missing parentheses in call to 'exec'")
ckmsg(s, "Missing parentheses in call to 'exec'. Did you mean exec(...)?")

s = 'exec f(a+b,c)'
ckmsg(s, "Missing parentheses in call to 'exec'.")
ckmsg(s, "Missing parentheses in call to 'exec'. Did you mean exec(...)?")

# should not apply to subclasses, see issue #31161
s = '''if True:\nprint "No indent"'''
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18 changes: 12 additions & 6 deletions Lib/test/test_print.py
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Expand Up @@ -140,21 +140,24 @@ def test_normal_string(self):
with self.assertRaises(SyntaxError) as context:
exec(python2_print_str)

self.assertIn('print("Hello World")', str(context.exception))
self.assertIn("Missing parentheses in call to 'print'. Did you mean print(...)",
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))
self.assertIn("Missing parentheses in call to 'print'. Did you mean print(...)",
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))
self.assertIn("Missing parentheses in call to 'print'. Did you mean print(...)",
str(context.exception))

def test_string_with_leading_whitespace(self):
python2_print_str = '''if 1:
Expand All @@ -163,7 +166,8 @@ def test_string_with_leading_whitespace(self):
with self.assertRaises(SyntaxError) as context:
exec(python2_print_str)

self.assertIn('print("Hello World")', str(context.exception))
self.assertIn("Missing parentheses in call to 'print'. Did you mean print(...)",
str(context.exception))

# bpo-32685: Suggestions for print statement should be proper when
# it is in the same line as the header of a compound statement
Expand All @@ -173,14 +177,16 @@ def test_string_with_semicolon(self):
with self.assertRaises(SyntaxError) as context:
exec(python2_print_str)

self.assertIn('print(p)', str(context.exception))
self.assertIn("Missing parentheses in call to 'print'. Did you mean print(...)",
str(context.exception))

def test_string_in_loop_on_same_line(self):
python2_print_str = 'for i in s: print i'
with self.assertRaises(SyntaxError) as context:
exec(python2_print_str)

self.assertIn('print(i)', str(context.exception))
self.assertIn("Missing parentheses in call to 'print'. Did you mean print(...)",
str(context.exception))

def test_stream_redirection_hint_for_py2_migration(self):
# Test correct hint produced for Py2 redirection syntax
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201 changes: 0 additions & 201 deletions Objects/exceptions.c
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Expand Up @@ -1475,9 +1475,6 @@ ComplexExtendsException(PyExc_Exception, AttributeError,
* SyntaxError extends Exception
*/

/* Helper function to customize error message for some syntax errors */
static int _report_missing_parentheses(PySyntaxErrorObject *self);

static int
SyntaxError_init(PySyntaxErrorObject *self, PyObject *args, PyObject *kwds)
{
Expand Down Expand Up @@ -1520,18 +1517,6 @@ SyntaxError_init(PySyntaxErrorObject *self, PyObject *args, PyObject *kwds)
PyErr_SetString(PyExc_TypeError, "end_offset must be provided when end_lineno is provided");
return -1;
}

/*
* Issue #21669: Custom error for 'print' & 'exec' as statements
*
* Only applies to SyntaxError instances, not to subclasses such
* as TabError or IndentationError (see issue #31161)
*/
if (Py_IS_TYPE(self, (PyTypeObject *)PyExc_SyntaxError) &&
self->text && PyUnicode_Check(self->text) &&
_report_missing_parentheses(self) < 0) {
return -1;
}
}
return 0;
}
Expand Down Expand Up @@ -3033,189 +3018,3 @@ _PyErr_TrySetFromCause(const char *format, ...)
PyErr_Restore(new_exc, new_val, new_tb);
return new_val;
}


/* To help with migration from Python 2, SyntaxError.__init__ applies some
* heuristics to try to report a more meaningful exception when print and
* exec are used like statements.
*
* The heuristics are currently expected to detect the following cases:
* - top level statement
* - statement in a nested suite
* - trailing section of a one line complex statement
*
* They're currently known not to trigger:
* - after a semi-colon
*
* The error message can be a bit odd in cases where the "arguments" are
* completely illegal syntactically, but that isn't worth the hassle of
* fixing.
*
* We also can't do anything about cases that are legal Python 3 syntax
* but mean something entirely different from what they did in Python 2
* (omitting the arguments entirely, printing items preceded by a unary plus
* 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)
{
// PRINT_OFFSET is to remove the `print ` prefix from the data.
const int PRINT_OFFSET = 6;
const int STRIP_BOTH = 2;
Py_ssize_t start_pos = start + PRINT_OFFSET;
Py_ssize_t text_len = PyUnicode_GET_LENGTH(self->text);
Py_UCS4 semicolon = ';';
Py_ssize_t end_pos = PyUnicode_FindChar(self->text, semicolon,
start_pos, text_len, 1);
if (end_pos < -1) {
return -1;
} else if (end_pos == -1) {
end_pos = text_len;
}

PyObject *data = PyUnicode_Substring(self->text, start_pos, end_pos);
if (data == NULL) {
return -1;
}

PyObject *strip_sep_obj = PyUnicode_FromString(" \t\r\n");
if (strip_sep_obj == NULL) {
Py_DECREF(data);
return -1;
}

PyObject *new_data = _PyUnicode_XStrip(data, STRIP_BOTH, 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)
{
/* Return values:
* -1: an error occurred
* 0: nothing happened
* 1: the check triggered & the error message was changed
*/
static PyObject *print_prefix = NULL;
static PyObject *exec_prefix = NULL;
Py_ssize_t text_len = PyUnicode_GET_LENGTH(self->text), match;
int kind = PyUnicode_KIND(self->text);
const void *data = PyUnicode_DATA(self->text);

/* Ignore leading whitespace */
while (start < text_len) {
Py_UCS4 ch = PyUnicode_READ(kind, data, start);
if (!Py_UNICODE_ISSPACE(ch))
break;
start++;
}
/* Checking against an empty or whitespace-only part of the string */
if (start == text_len) {
return 0;
}

/* Check for legacy print statements */
if (print_prefix == NULL) {
print_prefix = PyUnicode_InternFromString("print ");
if (print_prefix == NULL) {
return -1;
}
}
match = PyUnicode_Tailmatch(self->text, print_prefix,
start, text_len, -1);
if (match == -1) {
return -1;
}
if (match) {
return _set_legacy_print_statement_msg(self, start);
}

/* Check for legacy exec statements */
if (exec_prefix == NULL) {
exec_prefix = PyUnicode_InternFromString("exec ");
if (exec_prefix == NULL) {
return -1;
}
}
match = PyUnicode_Tailmatch(self->text, exec_prefix, start, text_len, -1);
if (match == -1) {
return -1;
}
if (match) {
PyObject *msg = PyUnicode_FromString("Missing parentheses in call "
"to 'exec'");
if (msg == NULL) {
return -1;
}
Py_XSETREF(self->msg, msg);
return 1;
}
/* Fall back to the default error message */
return 0;
}

static int
_report_missing_parentheses(PySyntaxErrorObject *self)
{
Py_UCS4 left_paren = 40;
Py_ssize_t left_paren_index;
Py_ssize_t text_len = PyUnicode_GET_LENGTH(self->text);
int legacy_check_result = 0;

/* Skip entirely if there is an opening parenthesis */
left_paren_index = PyUnicode_FindChar(self->text, left_paren,
0, text_len, 1);
if (left_paren_index < -1) {
return -1;
}
if (left_paren_index != -1) {
/* Use default error message for any line with an opening paren */
return 0;
}
/* Handle the simple statement case */
legacy_check_result = _check_for_legacy_statements(self, 0);
if (legacy_check_result < 0) {
return -1;

}
if (legacy_check_result == 0) {
/* Handle the one-line complex statement case */
Py_UCS4 colon = 58;
Py_ssize_t colon_index;
colon_index = PyUnicode_FindChar(self->text, colon,
0, text_len, 1);
if (colon_index < -1) {
return -1;
}
if (colon_index >= 0 && colon_index < text_len) {
/* Check again, starting from just after the colon */
if (_check_for_legacy_statements(self, colon_index+1) < 0) {
return -1;
}
}
}
return 0;
}
14 changes: 7 additions & 7 deletions Parser/parser.c
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Expand Up @@ -18158,7 +18158,7 @@ expression_without_invalid_rule(Parser *p)
return _res;
}

// invalid_legacy_expression: NAME expression_without_invalid
// invalid_legacy_expression: NAME star_expressions
static void *
invalid_legacy_expression_rule(Parser *p)
{
Expand All @@ -18169,22 +18169,22 @@ invalid_legacy_expression_rule(Parser *p)
}
void * _res = NULL;
int _mark = p->mark;
{ // NAME expression_without_invalid
{ // NAME star_expressions
if (p->error_indicator) {
D(p->level--);
return NULL;
}
D(fprintf(stderr, "%*c> invalid_legacy_expression[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "NAME expression_without_invalid"));
D(fprintf(stderr, "%*c> invalid_legacy_expression[%d-%d]: %s\n", p->level, ' ', _mark, p->mark, "NAME star_expressions"));
expr_ty a;
expr_ty b;
if (
(a = _PyPegen_name_token(p)) // NAME
&&
(b = expression_without_invalid_rule(p)) // expression_without_invalid
(b = star_expressions_rule(p)) // star_expressions
)
{
D(fprintf(stderr, "%*c+ invalid_legacy_expression[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "NAME expression_without_invalid"));
_res = _PyPegen_check_legacy_stmt ( p , a ) ? RAISE_SYNTAX_ERROR_KNOWN_RANGE ( a , b , "Missing parentheses in call to '%U'." , a -> v . Name . id ) : NULL;
D(fprintf(stderr, "%*c+ invalid_legacy_expression[%d-%d]: %s succeeded!\n", p->level, ' ', _mark, p->mark, "NAME star_expressions"));
_res = _PyPegen_check_legacy_stmt ( p , a ) ? RAISE_SYNTAX_ERROR_KNOWN_RANGE ( a , b , "Missing parentheses in call to '%U'. Did you mean %U(...)?" , a -> v . Name . id , a -> v . Name . id ) : NULL;
if (_res == NULL && PyErr_Occurred()) {
p->error_indicator = 1;
D(p->level--);
Expand All @@ -18194,7 +18194,7 @@ invalid_legacy_expression_rule(Parser *p)
}
p->mark = _mark;
D(fprintf(stderr, "%*c%s invalid_legacy_expression[%d-%d]: %s failed!\n", p->level, ' ',
p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "NAME expression_without_invalid"));
p->error_indicator ? "ERROR!" : "-", _mark, p->mark, "NAME star_expressions"));
}
_res = NULL;
done:
Expand Down