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bpo-40334: Disallow invalid single statements in the new parser #19774

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Merged
pablogsal merged 5 commits into from
Apr 29, 2020
Merged

bpo-40334: Disallow invalid single statements in the new parser #19774

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bpo-40334: Disallow invalid single statements in the new parser
lysnikolaou Apr 28, 2020
a9a60a7
Check if newline is allowed (preceded by linecont character or appear…
lysnikolaou Apr 28, 2020
4f11574
PEP 7
lysnikolaou Apr 29, 2020
6cbb27f
More PEP 7
lysnikolaou Apr 29, 2020
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lysnikolaou Apr 29, 2020
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1 change: 0 additions & 1 deletion Lib/test/test_compile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -501,7 +501,6 @@ def test_single_statement(self):
self.compile_single("if x:\n f(x)\nelse:\n g(x)")
self.compile_single("class T:\n pass")

@support.skip_if_new_parser('Pegen does not disallow multiline single stmts')
def test_bad_single_statement(self):
self.assertInvalidSingle('1\n2')
self.assertInvalidSingle('def f(): pass')
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51 changes: 51 additions & 0 deletions Parser/pegen/pegen.c
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Original file line number Diff line number Diff line change
Expand Up @@ -911,6 +911,52 @@ _PyPegen_number_token(Parser *p)
p->arena);
}

static int // bool
newline_in_string(Parser *p, const char *cur)
{
for (char c = *cur; cur >= p->tok->buf; c = *--cur) {
if (c == '\'' || c == '"') {
return 1;
}
}
return 0;
}

/* Check that the source for a single input statement really is a single
statement by looking at what is left in the buffer after parsing.
Trailing whitespace and comments are OK. */
static int // bool
bad_single_statement(Parser *p)
{
const char *cur = strchr(p->tok->buf, '\n');

/* Newlines are allowed if preceded by a line continuation character
or if they appear inside a string. */
if (!cur || *(cur - 1) == '\\' || newline_in_string(p, cur)) {
return 0;
}
char c = *cur;

for (;;) {
while (c == ' ' || c == '\t' || c == '\n' || c == '\014') {
c = *++cur;
}

if (!c) {
return 0;
}

if (c != '#') {
return 1;
}

/* Suck up comment. */
while (c && c != '\n') {
c = *++cur;
}
}
}

void
_PyPegen_Parser_Free(Parser *p)
{
Expand Down Expand Up @@ -1014,6 +1060,11 @@ _PyPegen_run_parser(Parser *p)
return NULL;
}

if (p->start_rule == Py_single_input && bad_single_statement(p)) {
p->tok->done = E_BADSINGLE; // This is not necessary for now, but might be in the future
return RAISE_SYNTAX_ERROR("multiple statements found while compiling a single statement");
}

return res;
}

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