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bpo-43897: Reject "_" captures and top-level MatchStar in the AST validator (GH-27432)

This commit is contained in:
Brandt Bucher 2021-07-28 17:24:18 -07:00 committed by GitHub
parent 92b5dc780d
commit 8d0647485d
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 33 additions and 21 deletions
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6
Lib/test/test_ast.py
View File

@ -1627,7 +1627,11 @@ class ASTValidatorTests(unittest.TestCase):
),
ast.MatchOr(
[pattern_1, pattern_x, ast.MatchSingleton('xxx')]
)
),
ast.MatchAs(name="_"),
ast.MatchStar(name="x"),
ast.MatchSequence([ast.MatchStar("_")]),
ast.MatchMapping([], [], rest="_"),
]
def test_match_validation_pattern(self):

48
Python/ast.c
View File

@ -20,7 +20,7 @@ static int validate_patterns(struct validator *, asdl_pattern_seq *, int);
static int _validate_nonempty_seq(asdl_seq *, const char *, const char *);
static int validate_stmt(struct validator *, stmt_ty);
static int validate_expr(struct validator *, expr_ty, expr_context_ty);
static int validate_pattern(struct validator *, pattern_ty);
static int validate_pattern(struct validator *, pattern_ty, int);
static int
validate_name(PyObject *name)
@ -493,7 +493,17 @@ validate_pattern_match_value(struct validator *state, expr_ty exp)
}
static int
validate_pattern(struct validator *state, pattern_ty p)
validate_capture(PyObject *name)
{
if (_PyUnicode_EqualToASCIIString(name, "_")) {
PyErr_Format(PyExc_ValueError, "can't capture name '_' in patterns");
return 0;
}
return validate_name(name);
}
static int
validate_pattern(struct validator *state, pattern_ty p, int star_ok)
{
int ret = -1;
if (++state->recursion_depth > state->recursion_limit) {
@ -501,8 +511,6 @@ validate_pattern(struct validator *state, pattern_ty p)
"maximum recursion depth exceeded during compilation");
return 0;
}
// Coming soon: https://bugs.python.org/issue43897 (thanks Batuhan)!
// TODO: Ensure no subnodes use "_" as an ordinary identifier
switch (p->kind) {
case MatchValue_kind:
ret = validate_pattern_match_value(state, p->v.MatchValue.value);
@ -525,7 +533,7 @@ validate_pattern(struct validator *state, pattern_ty p)
break;
}
if (p->v.MatchMapping.rest && !validate_name(p->v.MatchMapping.rest)) {
if (p->v.MatchMapping.rest && !validate_capture(p->v.MatchMapping.rest)) {
ret = 0;
break;
}
@ -575,16 +583,16 @@ validate_pattern(struct validator *state, pattern_ty p)
else {
PyErr_SetString(PyExc_ValueError,
"MatchClass cls field can only contain Name or Attribute nodes.");
state->recursion_depth--;
return 0;
ret = 0;
break;
}
}
for (Py_ssize_t i = 0; i < asdl_seq_LEN(p->v.MatchClass.kwd_attrs); i++) {
PyObject *identifier = asdl_seq_GET(p->v.MatchClass.kwd_attrs, i);
if (!validate_name(identifier)) {
state->recursion_depth--;
return 0;
ret = 0;
break;
}
}
@ -596,10 +604,15 @@ validate_pattern(struct validator *state, pattern_ty p)
ret = validate_patterns(state, p->v.MatchClass.kwd_patterns, /*star_ok=*/0);
break;
case MatchStar_kind:
ret = p->v.MatchStar.name == NULL || validate_name(p->v.MatchStar.name);
if (!star_ok) {
PyErr_SetString(PyExc_ValueError, "can't use MatchStar here");
ret = 0;
break;
}
ret = p->v.MatchStar.name == NULL || validate_capture(p->v.MatchStar.name);
break;
case MatchAs_kind:
if (p->v.MatchAs.name && !validate_name(p->v.MatchAs.name)) {
if (p->v.MatchAs.name && !validate_capture(p->v.MatchAs.name)) {
ret = 0;
break;
}
@ -609,10 +622,10 @@ validate_pattern(struct validator *state, pattern_ty p)
else if (p->v.MatchAs.name == NULL) {
PyErr_SetString(PyExc_ValueError,
"MatchAs must specify a target name if a pattern is given");
return 0;
ret = 0;
}
else {
ret = validate_pattern(state, p->v.MatchAs.pattern);
ret = validate_pattern(state, p->v.MatchAs.pattern, /*star_ok=*/0);
}
break;
case MatchOr_kind:
@ -759,7 +772,7 @@ validate_stmt(struct validator *state, stmt_ty stmt)
}
for (i = 0; i < asdl_seq_LEN(stmt->v.Match.cases); i++) {
match_case_ty m = asdl_seq_GET(stmt->v.Match.cases, i);
if (!validate_pattern(state, m->pattern)
if (!validate_pattern(state, m->pattern, /*star_ok=*/0)
|| (m->guard && !validate_expr(state, m->guard, Load))
|| !validate_body(state, m->body, "match_case")) {
return 0;
@ -894,12 +907,7 @@ validate_patterns(struct validator *state, asdl_pattern_seq *patterns, int star_
Py_ssize_t i;
for (i = 0; i < asdl_seq_LEN(patterns); i++) {
pattern_ty pattern = asdl_seq_GET(patterns, i);
if (pattern->kind == MatchStar_kind && !star_ok) {
PyErr_SetString(PyExc_ValueError,
"Can't use MatchStar within this sequence of patterns");
return 0;
}
if (!validate_pattern(state, pattern)) {
if (!validate_pattern(state, pattern, star_ok)) {
return 0;
}
}