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bpo-40334: Fix error location upon parsing an invalid string literal (p…
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…ythonGH-19962)

When parsing a string with an invalid escape, the old parser used to
point to the beginning of the invalid string. This commit changes the new
parser to match that behaviour, since it's currently pointing to the
end of the string (or to be more precise, to the beginning of the next
token).
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@lysnikolaou
lysnikolaou authored May 7, 2020
1 parent 3466922 commit 2f37c35
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Showing 6 changed files with 34 additions and 28 deletions.
2 changes: 1 addition & 1 deletion Lib/test/test_cmd_line_script.py
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Original file line number Diff line number Diff line change
Expand Up @@ -648,7 +648,7 @@ def test_syntaxerror_invalid_escape_sequence_multi_line(self):
self.assertEqual(
stderr.splitlines()[-3:],
[ b' foo = """\\q"""',
b' ^',
b' ^',
b'SyntaxError: invalid escape sequence \\q'
],
)
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7 changes: 3 additions & 4 deletions Lib/test/test_string_literals.py
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Original file line number Diff line number Diff line change
Expand Up @@ -118,8 +118,7 @@ def test_eval_str_invalid_escape(self):
eval("'''\n\\z'''")
self.assertEqual(len(w), 1)
self.assertEqual(w[0].filename, '<string>')
if use_old_parser():
self.assertEqual(w[0].lineno, 1)
self.assertEqual(w[0].lineno, 1)

with warnings.catch_warnings(record=True) as w:
warnings.simplefilter('error', category=DeprecationWarning)
Expand All @@ -128,8 +127,8 @@ def test_eval_str_invalid_escape(self):
exc = cm.exception
self.assertEqual(w, [])
self.assertEqual(exc.filename, '<string>')
if use_old_parser():
self.assertEqual(exc.lineno, 1)
self.assertEqual(exc.lineno, 1)
self.assertEqual(exc.offset, 1)

def test_eval_str_raw(self):
self.assertEqual(eval(""" r'x' """), 'x')
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38 changes: 24 additions & 14 deletions Parser/pegen/parse_string.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12,19 +12,24 @@
// file (like "_PyPegen_raise_syntax_error").

static int
warn_invalid_escape_sequence(Parser *p, unsigned char first_invalid_escape_char)
warn_invalid_escape_sequence(Parser *p, unsigned char first_invalid_escape_char, Token *t)
{
PyObject *msg =
PyUnicode_FromFormat("invalid escape sequence \\%c", first_invalid_escape_char);
if (msg == NULL) {
return -1;
}
if (PyErr_WarnExplicitObject(PyExc_DeprecationWarning, msg, p->tok->filename,
p->tok->lineno, NULL, NULL) < 0) {
t->lineno, NULL, NULL) < 0) {
if (PyErr_ExceptionMatches(PyExc_DeprecationWarning)) {
/* Replace the DeprecationWarning exception with a SyntaxError
to get a more accurate error report */
PyErr_Clear();

/* This is needed, in order for the SyntaxError to point to the token t,
since _PyPegen_raise_error uses p->tokens[p->fill - 1] for the
error location, if p->known_err_token is not set. */
p->known_err_token = t;
RAISE_SYNTAX_ERROR("invalid escape sequence \\%c", first_invalid_escape_char);
}
Py_DECREF(msg);
Expand All @@ -47,7 +52,7 @@ decode_utf8(const char **sPtr, const char *end)
}

static PyObject *
decode_unicode_with_escapes(Parser *parser, const char *s, size_t len)
decode_unicode_with_escapes(Parser *parser, const char *s, size_t len, Token *t)
{
PyObject *v, *u;
char *buf;
Expand Down Expand Up @@ -110,7 +115,7 @@ decode_unicode_with_escapes(Parser *parser, const char *s, size_t len)
v = _PyUnicode_DecodeUnicodeEscape(s, len, NULL, &first_invalid_escape);

if (v != NULL && first_invalid_escape != NULL) {
if (warn_invalid_escape_sequence(parser, *first_invalid_escape) < 0) {
if (warn_invalid_escape_sequence(parser, *first_invalid_escape, t) < 0) {
/* We have not decref u before because first_invalid_escape points
inside u. */
Py_XDECREF(u);
Expand All @@ -123,7 +128,7 @@ decode_unicode_with_escapes(Parser *parser, const char *s, size_t len)
}

static PyObject *
decode_bytes_with_escapes(Parser *p, const char *s, Py_ssize_t len)
decode_bytes_with_escapes(Parser *p, const char *s, Py_ssize_t len, Token *t)
{
const char *first_invalid_escape;
PyObject *result = _PyBytes_DecodeEscape(s, len, NULL, &first_invalid_escape);
Expand All @@ -132,7 +137,7 @@ decode_bytes_with_escapes(Parser *p, const char *s, Py_ssize_t len)
}

if (first_invalid_escape != NULL) {
if (warn_invalid_escape_sequence(p, *first_invalid_escape) < 0) {
if (warn_invalid_escape_sequence(p, *first_invalid_escape, t) < 0) {
Py_DECREF(result);
return NULL;
}
Expand All @@ -146,9 +151,14 @@ decode_bytes_with_escapes(Parser *p, const char *s, Py_ssize_t len)
If the string is an f-string, set *fstr and *fstrlen to the unparsed
string object. Return 0 if no errors occurred. */
int
_PyPegen_parsestr(Parser *p, const char *s, int *bytesmode, int *rawmode, PyObject **result,
const char **fstr, Py_ssize_t *fstrlen)
_PyPegen_parsestr(Parser *p, int *bytesmode, int *rawmode, PyObject **result,
const char **fstr, Py_ssize_t *fstrlen, Token *t)
{
const char *s = PyBytes_AsString(t->bytes);
if (s == NULL) {
return -1;
}

size_t len;
int quote = Py_CHARMASK(*s);
int fmode = 0;
Expand Down Expand Up @@ -245,15 +255,15 @@ _PyPegen_parsestr(Parser *p, const char *s, int *bytesmode, int *rawmode, PyObje
*result = PyBytes_FromStringAndSize(s, len);
}
else {
*result = decode_bytes_with_escapes(p, s, len);
*result = decode_bytes_with_escapes(p, s, len, t);
}
}
else {
if (*rawmode) {
*result = PyUnicode_DecodeUTF8Stateful(s, len, NULL, NULL);
}
else {
*result = decode_unicode_with_escapes(p, s, len);
*result = decode_unicode_with_escapes(p, s, len, t);
}
}
return *result == NULL ? -1 : 0;
Expand Down Expand Up @@ -637,7 +647,7 @@ fstring_compile_expr(Parser *p, const char *expr_start, const char *expr_end,
*/
static int
fstring_find_literal(Parser *p, const char **str, const char *end, int raw,
PyObject **literal, int recurse_lvl)
PyObject **literal, int recurse_lvl, Token *t)
{
/* Get any literal string. It ends when we hit an un-doubled left
brace (which isn't part of a unicode name escape such as
Expand All @@ -660,7 +670,7 @@ fstring_find_literal(Parser *p, const char **str, const char *end, int raw,
}
break;
}
if (ch == '{' && warn_invalid_escape_sequence(p, ch) < 0) {
if (ch == '{' && warn_invalid_escape_sequence(p, ch, t) < 0) {
return -1;
}
}
Expand Down Expand Up @@ -704,7 +714,7 @@ fstring_find_literal(Parser *p, const char **str, const char *end, int raw,
NULL, NULL);
else
*literal = decode_unicode_with_escapes(p, literal_start,
s - literal_start);
s - literal_start, t);
if (!*literal)
return -1;
}
Expand Down Expand Up @@ -1041,7 +1051,7 @@ fstring_find_literal_and_expr(Parser *p, const char **str, const char *end, int
assert(*literal == NULL && *expression == NULL);

/* Get any literal string. */
result = fstring_find_literal(p, str, end, raw, literal, recurse_lvl);
result = fstring_find_literal(p, str, end, raw, literal, recurse_lvl, t);
if (result < 0)
goto error;

Expand Down
4 changes: 2 additions & 2 deletions Parser/pegen/parse_string.h
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Original file line number Diff line number Diff line change
Expand Up @@ -34,8 +34,8 @@ typedef struct {
} FstringParser;

void _PyPegen_FstringParser_Init(FstringParser *);
int _PyPegen_parsestr(Parser *, const char *, int *, int *, PyObject **,
const char **, Py_ssize_t *);
int _PyPegen_parsestr(Parser *, int *, int *, PyObject **,
const char **, Py_ssize_t *, Token *);
int _PyPegen_FstringParser_ConcatFstring(Parser *, FstringParser *, const char **,
const char *, int, int, Token *, Token *,
Token *);
Expand Down
10 changes: 3 additions & 7 deletions Parser/pegen/pegen.c
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Original file line number Diff line number Diff line change
Expand Up @@ -383,7 +383,7 @@ _PyPegen_raise_error(Parser *p, PyObject *errtype, int with_col_number, const ch
PyObject *errstr = NULL;
PyObject *loc = NULL;
PyObject *tmp = NULL;
Token *t = p->tokens[p->fill - 1];
Token *t = p->known_err_token != NULL ? p->known_err_token : p->tokens[p->fill - 1];
Py_ssize_t col_number = !with_col_number;
va_list va;
p->error_indicator = 1;
Expand Down Expand Up @@ -1053,6 +1053,7 @@ _PyPegen_Parser_New(struct tok_state *tok, int start_rule, int flags,
p->starting_col_offset = 0;
p->flags = flags;
p->feature_version = feature_version;
p->known_err_token = NULL;

return p;
}
Expand Down Expand Up @@ -1972,12 +1973,7 @@ _PyPegen_concatenate_strings(Parser *p, asdl_seq *strings)
const char *fstr;
Py_ssize_t fstrlen = -1;

char *this_str = PyBytes_AsString(t->bytes);
if (!this_str) {
goto error;
}

if (_PyPegen_parsestr(p, this_str, &this_bytesmode, &this_rawmode, &s, &fstr, &fstrlen) != 0) {
if (_PyPegen_parsestr(p, &this_bytesmode, &this_rawmode, &s, &fstr, &fstrlen, t) != 0) {
goto error;
}

Expand Down
1 change: 1 addition & 0 deletions Parser/pegen/pegen.h
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,7 @@ typedef struct {
int flags;
int feature_version;
growable_comment_array type_ignore_comments;
Token *known_err_token;
} Parser;

typedef struct {
Expand Down

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