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[3.10] bpo-43897: ast validation for pattern matching nodes #27074

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Merged
pablogsal merged 1 commit into from
Jul 10, 2021
Merged

[3.10] bpo-43897: ast validation for pattern matching nodes #27074

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143 changes: 142 additions & 1 deletion Lib/test/test_ast.py
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -695,7 +695,7 @@ def test_constant_as_name(self):
for constant in "True", "False", "None":
expr = ast.Expression(ast.Name(constant, ast.Load()))
ast.fix_missing_locations(expr)
with self.assertRaisesRegex(ValueError, f"Name node can't be used with '{constant}' constant"):
with self.assertRaisesRegex(ValueError, f"identifier field can't represent '{constant}' constant"):
compile(expr, "<test>", "eval")


Expand Down Expand Up @@ -1476,6 +1476,147 @@ def test_stdlib_validates(self):
mod = ast.parse(source, fn)
compile(mod, fn, "exec")

constant_1 = ast.Constant(1)
pattern_1 = ast.MatchValue(constant_1)

constant_x = ast.Constant('x')
pattern_x = ast.MatchValue(constant_x)

constant_true = ast.Constant(True)
pattern_true = ast.MatchSingleton(True)

name_carter = ast.Name('carter', ast.Load())

_MATCH_PATTERNS = [
ast.MatchValue(
ast.Attribute(
ast.Attribute(
ast.Name('x', ast.Store()),
'y', ast.Load()
),
'z', ast.Load()
)
),
ast.MatchValue(
ast.Attribute(
ast.Attribute(
ast.Name('x', ast.Load()),
'y', ast.Store()
),
'z', ast.Load()
)
),
ast.MatchValue(
ast.Constant(...)
),
ast.MatchValue(
ast.Constant(True)
),
ast.MatchValue(
ast.Constant((1,2,3))
),
ast.MatchSingleton('string'),
ast.MatchSequence([
ast.MatchSingleton('string')
]),
ast.MatchSequence(
[
ast.MatchSequence(
[
ast.MatchSingleton('string')
]
)
]
),
ast.MatchMapping(
[constant_1, constant_true],
[pattern_x]
),
ast.MatchMapping(
[constant_true, constant_1],
[pattern_x, pattern_1],
rest='True'
),
ast.MatchMapping(
[constant_true, ast.Starred(ast.Name('lol', ast.Load()), ast.Load())],
[pattern_x, pattern_1],
rest='legit'
),
ast.MatchClass(
ast.Attribute(
ast.Attribute(
constant_x,
'y', ast.Load()),
'z', ast.Load()),
patterns=[], kwd_attrs=[], kwd_patterns=[]
),
ast.MatchClass(
name_carter,
patterns=[],
kwd_attrs=['True'],
kwd_patterns=[pattern_1]
),
ast.MatchClass(
name_carter,
patterns=[],
kwd_attrs=[],
kwd_patterns=[pattern_1]
),
ast.MatchClass(
name_carter,
patterns=[ast.MatchSingleton('string')],
kwd_attrs=[],
kwd_patterns=[]
),
ast.MatchClass(
name_carter,
patterns=[ast.MatchStar()],
kwd_attrs=[],
kwd_patterns=[]
),
ast.MatchClass(
name_carter,
patterns=[],
kwd_attrs=[],
kwd_patterns=[ast.MatchStar()]
),
ast.MatchSequence(
[
ast.MatchStar("True")
]
),
ast.MatchAs(
name='False'
),
ast.MatchOr(
[]
),
ast.MatchOr(
[pattern_1]
),
ast.MatchOr(
[pattern_1, pattern_x, ast.MatchSingleton('xxx')]
)
]

def test_match_validation_pattern(self):
name_x = ast.Name('x', ast.Load())
for pattern in self._MATCH_PATTERNS:
with self.subTest(ast.dump(pattern, indent=4)):
node = ast.Match(
subject=name_x,
cases = [
ast.match_case(
pattern=pattern,
body = [ast.Pass()]
)
]
)
node = ast.fix_missing_locations(node)
module = ast.Module([node], [])
with self.assertRaises(ValueError):
compile(module, "<test>", "exec")


class ConstantTests(unittest.TestCase):
"""Tests on the ast.Constant node type."""
Expand Down
154 changes: 123 additions & 31 deletions Python/ast.c
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -15,7 +15,8 @@ struct validator {
};

static int validate_stmts(struct validator *, asdl_stmt_seq *);
static int validate_exprs(struct validator *, asdl_expr_seq*, expr_context_ty, int);
static int validate_exprs(struct validator *, asdl_expr_seq *, expr_context_ty, int);
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);
Expand All @@ -33,7 +34,7 @@ validate_name(PyObject *name)
};
for (int i = 0; forbidden[i] != NULL; i++) {
if (_PyUnicode_EqualToASCIIString(name, forbidden[i])) {
PyErr_Format(PyExc_ValueError, "Name node can't be used with '%s' constant", forbidden[i]);
PyErr_Format(PyExc_ValueError, "identifier field can't represent '%s' constant", forbidden[i]);
return 0;
}
}
Expand Down Expand Up @@ -448,6 +449,21 @@ validate_pattern_match_value(struct validator *state, expr_ty exp)
switch (exp->kind)
{
case Constant_kind:
/* Ellipsis and immutable sequences are not allowed.
For True, False and None, MatchSingleton() should
be used */
if (!validate_expr(state, exp, Load)) {
return 0;
}
PyObject *literal = exp->v.Constant.value;
if (PyLong_CheckExact(literal) || PyFloat_CheckExact(literal) ||
PyBytes_CheckExact(literal) || PyComplex_CheckExact(literal) ||
PyUnicode_CheckExact(literal)) {
return 1;
}
PyErr_SetString(PyExc_ValueError,
"unexpected constant inside of a literal pattern");
return 0;
case Attribute_kind:
// Constants and attribute lookups are always permitted
return 1;
Expand All @@ -465,11 +481,14 @@ validate_pattern_match_value(struct validator *state, expr_ty exp)
return 1;
}
break;
case JoinedStr_kind:
// Handled in the later stages
return 1;
default:
break;
}
PyErr_SetString(PyExc_SyntaxError,
"patterns may only match literals and attribute lookups");
PyErr_SetString(PyExc_ValueError,
"patterns may only match literals and attribute lookups");
return 0;
}

Expand All @@ -489,51 +508,101 @@ validate_pattern(struct validator *state, pattern_ty p)
ret = validate_pattern_match_value(state, p->v.MatchValue.value);
break;
case MatchSingleton_kind:
// TODO: Check constant is specifically None, True, or False
ret = validate_constant(state, p->v.MatchSingleton.value);
ret = p->v.MatchSingleton.value == Py_None || PyBool_Check(p->v.MatchSingleton.value);
if (!ret) {
PyErr_SetString(PyExc_ValueError,
"MatchSingleton can only contain True, False and None");
}
break;
case MatchSequence_kind:
// TODO: Validate all subpatterns
// return validate_patterns(state, p->v.MatchSequence.patterns);
ret = 1;
ret = validate_patterns(state, p->v.MatchSequence.patterns, /*star_ok=*/1);
break;
case MatchMapping_kind:
// TODO: check "rest" target name is valid
if (asdl_seq_LEN(p->v.MatchMapping.keys) != asdl_seq_LEN(p->v.MatchMapping.patterns)) {
PyErr_SetString(PyExc_ValueError,
"MatchMapping doesn't have the same number of keys as patterns");
return 0;
ret = 0;
break;
}
// null_ok=0 for key expressions, as rest-of-mapping is captured in "rest"
// TODO: replace with more restrictive expression validator, as per MatchValue above
if (!validate_exprs(state, p->v.MatchMapping.keys, Load, /*null_ok=*/ 0)) {
return 0;

if (p->v.MatchMapping.rest && !validate_name(p->v.MatchMapping.rest)) {
ret = 0;
break;
}
// TODO: Validate all subpatterns
// ret = validate_patterns(state, p->v.MatchMapping.patterns);
ret = 1;

asdl_expr_seq *keys = p->v.MatchMapping.keys;
for (Py_ssize_t i = 0; i < asdl_seq_LEN(keys); i++) {
expr_ty key = asdl_seq_GET(keys, i);
if (key->kind == Constant_kind) {
PyObject *literal = key->v.Constant.value;
if (literal == Py_None || PyBool_Check(literal)) {
/* validate_pattern_match_value will ensure the key
doesn't contain True, False and None but it is
syntactically valid, so we will pass those on in
a special case. */
continue;
}
}
if (!validate_pattern_match_value(state, key)) {
ret = 0;
break;
}
}

ret = validate_patterns(state, p->v.MatchMapping.patterns, /*star_ok=*/0);
break;
case MatchClass_kind:
if (asdl_seq_LEN(p->v.MatchClass.kwd_attrs) != asdl_seq_LEN(p->v.MatchClass.kwd_patterns)) {
PyErr_SetString(PyExc_ValueError,
"MatchClass doesn't have the same number of keyword attributes as patterns");
return 0;
ret = 0;
break;
}
// TODO: Restrict cls lookup to being a name or attribute
if (!validate_expr(state, p->v.MatchClass.cls, Load)) {
return 0;
ret = 0;
break;
}
// TODO: Validate all subpatterns
// return validate_patterns(state, p->v.MatchClass.patterns) &&
// validate_patterns(state, p->v.MatchClass.kwd_patterns);
ret = 1;

expr_ty cls = p->v.MatchClass.cls;
while (1) {
if (cls->kind == Name_kind) {
break;
}
else if (cls->kind == Attribute_kind) {
cls = cls->v.Attribute.value;
continue;
}
else {
PyErr_SetString(PyExc_ValueError,
"MatchClass cls field can only contain Name or Attribute nodes.");
state->recursion_depth--;
return 0;
}
}

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;
}
}

if (!validate_patterns(state, p->v.MatchClass.patterns, /*star_ok=*/0)) {
ret = 0;
break;
}

ret = validate_patterns(state, p->v.MatchClass.kwd_patterns, /*star_ok=*/0);
break;
case MatchStar_kind:
// TODO: check target name is valid
ret = 1;
ret = p->v.MatchStar.name == NULL || validate_name(p->v.MatchStar.name);
break;
case MatchAs_kind:
// TODO: check target name is valid
if (p->v.MatchAs.name && !validate_name(p->v.MatchAs.name)) {
ret = 0;
break;
}
if (p->v.MatchAs.pattern == NULL) {
ret = 1;
}
Expand All @@ -547,9 +616,13 @@ validate_pattern(struct validator *state, pattern_ty p)
}
break;
case MatchOr_kind:
// TODO: Validate all subpatterns
// return validate_patterns(state, p->v.MatchOr.patterns);
ret = 1;
if (asdl_seq_LEN(p->v.MatchOr.patterns) < 2) {
PyErr_SetString(PyExc_ValueError,
"MatchOr requires at least 2 patterns");
ret = 0;
break;
}
ret = validate_patterns(state, p->v.MatchOr.patterns, /*star_ok=*/0);
break;
// No default case, so the compiler will emit a warning if new pattern
// kinds are added without being handled here
Expand Down Expand Up @@ -815,6 +888,25 @@ validate_exprs(struct validator *state, asdl_expr_seq *exprs, expr_context_ty ct
return 1;
}

static int
validate_patterns(struct validator *state, asdl_pattern_seq *patterns, int star_ok)
{
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)) {
return 0;
}
}
return 1;
}


/* See comments in symtable.c. */
#define COMPILER_STACK_FRAME_SCALE 3

Expand Down