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gh-104374: Remove access to class scopes for inlined comprehensions by JelleZijlstra · Pull Request #104528 · python/cpython · GitHub

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gh-104374: Remove access to class scopes for inlined comprehensions #104528

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Merged
JelleZijlstra merged 10 commits into from
May 18, 2023
Conversation 19 Commits 10 Checks 0 Files changed
Merged

gh-104374: Remove access to class scopes for inlined comprehensions #104528

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3fad7b0
gh-104374: Remove access to class scopes for inlined comprehensions
JelleZijlstra May 16, 2023
fa11ca9
Update Lib/test/test_listcomps.py
JelleZijlstra May 16, 2023
1d776fd
Remove unnecessary change
JelleZijlstra May 16, 2023
932a2da
Better tests, copied from Carl's PR
JelleZijlstra May 16, 2023
d5653ae
A few more tests
JelleZijlstra May 16, 2023
ba3bacf
Merge remote-tracking branch 'upstream/main' into classcomp2
JelleZijlstra May 16, 2023
948bc1a
fix definition of 'in a class block'
carljm May 17, 2023
045478f
a couple more tests
carljm May 17, 2023
fc63272
Merge remote-tracking branch 'upstream/main' into classcomp2
JelleZijlstra May 18, 2023
afe0277
A few more tests
JelleZijlstra May 18, 2023
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109 changes: 107 additions & 2 deletions Lib/test/test_listcomps.py
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Original file line number Diff line number Diff line change
Expand Up @@ -200,7 +200,8 @@ def f():
y = [g for x in [1]]
"""
outputs = {"y": [2]}
self._check_in_scopes(code, outputs)
self._check_in_scopes(code, outputs, scopes=["module", "function"])
self._check_in_scopes(code, scopes=["class"], raises=NameError)

def test_inner_cell_shadows_outer_redefined(self):
code = """
Expand Down Expand Up @@ -328,7 +329,8 @@ def test_nested_2(self):
y = [x for [x ** x for x in range(x)][x - 1] in l]
"""
outputs = {"y": [3, 3, 3]}
self._check_in_scopes(code, outputs)
self._check_in_scopes(code, outputs, scopes=["module", "function"])
self._check_in_scopes(code, scopes=["class"], raises=NameError)

def test_nested_3(self):
code = """
Expand Down Expand Up @@ -379,6 +381,109 @@ def f():
with self.assertRaises(UnboundLocalError):
f()

def test_name_error_in_class_scope(self):
code = """
y = 1
[x + y for x in range(2)]
"""
self._check_in_scopes(code, raises=NameError, scopes=["class"])

def test_global_in_class_scope(self):
code = """
y = 2
vals = [(x, y) for x in range(2)]
"""
outputs = {"vals": [(0, 1), (1, 1)]}
self._check_in_scopes(code, outputs, ns={"y": 1}, scopes=["class"])

def test_in_class_scope_inside_function_1(self):
code = """
class C:
y = 2
vals = [(x, y) for x in range(2)]
vals = C.vals
"""
outputs = {"vals": [(0, 1), (1, 1)]}
self._check_in_scopes(code, outputs, ns={"y": 1}, scopes=["function"])

def test_in_class_scope_inside_function_2(self):
code = """
y = 1
class C:
y = 2
vals = [(x, y) for x in range(2)]
vals = C.vals
"""
outputs = {"vals": [(0, 1), (1, 1)]}
self._check_in_scopes(code, outputs, scopes=["function"])

def test_in_class_scope_with_global(self):
code = """
y = 1
class C:
global y
y = 2
# Ensure the listcomp uses the global, not the value in the
# class namespace
locals()['y'] = 3
vals = [(x, y) for x in range(2)]
vals = C.vals
"""
outputs = {"vals": [(0, 2), (1, 2)]}
self._check_in_scopes(code, outputs, scopes=["module", "class"])
outputs = {"vals": [(0, 1), (1, 1)]}
self._check_in_scopes(code, outputs, scopes=["function"])

def test_in_class_scope_with_nonlocal(self):
code = """
y = 1
class C:
nonlocal y
y = 2
# Ensure the listcomp uses the global, not the value in the
# class namespace
locals()['y'] = 3
vals = [(x, y) for x in range(2)]
vals = C.vals
"""
outputs = {"vals": [(0, 2), (1, 2)]}
self._check_in_scopes(code, outputs, scopes=["function"])

def test_nested_has_free_var(self):
code = """
items = [a for a in [1] if [a for _ in [0]]]
"""
outputs = {"items": [1]}
self._check_in_scopes(code, outputs, scopes=["class"])

def test_nested_free_var_not_bound_in_outer_comp(self):
code = """
z = 1
items = [a for a in [1] if [x for x in [1] if z]]
"""
self._check_in_scopes(code, {"items": [1]}, scopes=["module", "function"])
self._check_in_scopes(code, {"items": []}, ns={"z": 0}, scopes=["class"])

def test_nested_free_var_in_iter(self):
code = """
items = [_C for _C in [1] for [0, 1][[x for x in [1] if _C][0]] in [2]]

JelleZijlstra May 17, 2023

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Would be nice if we could test here that the name resolution in the inner listcomp here is right. I'll try to come up with some more tests around nested listcomps.

carljm May 18, 2023

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Are you still planning to add more tests here, or improve this one?

JelleZijlstra May 18, 2023

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Yes, will push some more tests today or tomorrow. If you'd prefer to merge this now we can also do that; I can just write more tests in another PR.

carljm May 18, 2023

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Yes, I think if we get known fixes merged sooner it's easier to do more effective fuzz testing; if we find more issues we can fix them in separate PRs, and we can add more tests that we think of in separate PRs.

JelleZijlstra May 18, 2023

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Just added two more tests and turned on automerge.
"""
self._check_in_scopes(code, {"items": [1]})

def test_nested_free_var_in_expr(self):
code = """
items = [(_C, [x for x in [1] if _C]) for _C in [0, 1]]
"""
self._check_in_scopes(code, {"items": [(0, []), (1, [1])]})

def test_nested_listcomp_in_lambda(self):
code = """
f = [(z, lambda y: [(x, y, z) for x in [3]]) for z in [1]]
(z, func), = f
out = func(2)
"""
self._check_in_scopes(code, {"z": 1, "out": [(3, 2, 1)]})


__test__ = {'doctests' : doctests}

Expand Down
20 changes: 15 additions & 5 deletions Python/compile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -388,6 +388,8 @@ struct compiler_unit {
instr_sequence u_instr_sequence; /* codegen output */

int u_nfblocks;
int u_in_inlined_comp;

struct fblockinfo u_fblock[CO_MAXBLOCKS];

_PyCompile_CodeUnitMetadata u_metadata;
Expand Down Expand Up @@ -1290,6 +1292,7 @@ compiler_enter_scope(struct compiler *c, identifier name,
}

u->u_nfblocks = 0;
u->u_in_inlined_comp = 0;
u->u_metadata.u_firstlineno = lineno;
u->u_metadata.u_consts = PyDict_New();
if (!u->u_metadata.u_consts) {
Expand Down Expand Up @@ -4137,7 +4140,7 @@ compiler_nameop(struct compiler *c, location loc,
case OP_DEREF:
switch (ctx) {
case Load:
if (c->u->u_ste->ste_type == ClassBlock) {
if (c->u->u_ste->ste_type == ClassBlock && !c->u->u_in_inlined_comp) {
op = LOAD_FROM_DICT_OR_DEREF;
// First load the locals
if (codegen_addop_noarg(INSTR_SEQUENCE(c), LOAD_LOCALS, loc) < 0) {
Expand Down Expand Up @@ -4188,7 +4191,12 @@ compiler_nameop(struct compiler *c, location loc,
break;
case OP_NAME:
switch (ctx) {
case Load: op = LOAD_NAME; break;
case Load:
op = (c->u->u_ste->ste_type == ClassBlock
&& c->u->u_in_inlined_comp)
? LOAD_GLOBAL
: LOAD_NAME;
break;
case Store: op = STORE_NAME; break;
case Del: op = DELETE_NAME; break;
}
Expand Down Expand Up @@ -5415,6 +5423,8 @@ push_inlined_comprehension_state(struct compiler *c, location loc,
PySTEntryObject *entry,
inlined_comprehension_state *state)
{
int in_class_block = (c->u->u_ste->ste_type == ClassBlock) && !c->u->u_in_inlined_comp;
c->u->u_in_inlined_comp++;
// iterate over names bound in the comprehension and ensure we isolate
// them from the outer scope as needed
PyObject *k, *v;
Expand All @@ -5426,7 +5436,7 @@ push_inlined_comprehension_state(struct compiler *c, location loc,
// at all; DEF_LOCAL | DEF_NONLOCAL can occur in the case of an
// assignment expression to a nonlocal in the comprehension, these don't
// need handling here since they shouldn't be isolated
if (symbol & DEF_LOCAL && !(symbol & DEF_NONLOCAL)) {
if ((symbol & DEF_LOCAL && !(symbol & DEF_NONLOCAL)) || in_class_block) {
if (!_PyST_IsFunctionLike(c->u->u_ste)) {
// non-function scope: override this name to use fast locals
PyObject *orig = PyDict_GetItem(c->u->u_metadata.u_fasthidden, k);
Expand All @@ -5448,8 +5458,7 @@ push_inlined_comprehension_state(struct compiler *c, location loc,
long scope = (symbol >> SCOPE_OFFSET) & SCOPE_MASK;
PyObject *outv = PyDict_GetItemWithError(c->u->u_ste->ste_symbols, k);
if (outv == NULL) {
assert(PyErr_Occurred());
return ERROR;
outv = _PyLong_GetZero();
}
assert(PyLong_Check(outv));
long outsc = (PyLong_AS_LONG(outv) >> SCOPE_OFFSET) & SCOPE_MASK;
Expand Down Expand Up @@ -5523,6 +5532,7 @@ static int
pop_inlined_comprehension_state(struct compiler *c, location loc,
inlined_comprehension_state state)
{
c->u->u_in_inlined_comp--;
PyObject *k, *v;
Py_ssize_t pos = 0;
if (state.temp_symbols) {
Expand Down
5 changes: 3 additions & 2 deletions Python/symtable.c
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Expand Up @@ -674,8 +674,9 @@ inline_comprehension(PySTEntryObject *ste, PySTEntryObject *comp,
}

// free vars in comprehension that are locals in outer scope can
// now simply be locals, unless they are free in comp children
if (!is_free_in_any_child(comp, k)) {
// now simply be locals, unless they are free in comp children,
// or if the outer scope is a class block
if (!is_free_in_any_child(comp, k) && ste->ste_type != ClassBlock) {
if (PySet_Discard(comp_free, k) < 0) {
return 0;
}
Expand Down
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