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Detect bad list.append calls without a varname #522

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merged 2 commits into from
Apr 14, 2022
Merged

Detect bad list.append calls without a varname #522

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ba626bd
Detect bad list.append calls without a varname
JelleZijlstra Apr 14, 2022
0dc3979
fix test
JelleZijlstra Apr 14, 2022
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2 changes: 2 additions & 0 deletions docs/changelog.md
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,8 @@

## Unreleased

- Detect incompatible types for some calls to `list.append`,
`list.extend`, `list.__add__`, and `set.add` (#522)
- Optimize local variables with very complex inferred types (#521)

## Version 0.7.0 (April 13, 2022)
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34 changes: 15 additions & 19 deletions pyanalyze/implementation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -352,20 +352,20 @@ def inner(iterable: Value) -> Value:
def _list_append_impl(ctx: CallContext) -> ImplReturn:
lst = replace_known_sequence_value(ctx.vars["self"])
element = ctx.vars["object"]
varname = ctx.visitor.varname_for_self_constraint(ctx.node)
if varname is not None:
if isinstance(lst, SequenceValue):
if isinstance(lst, SequenceValue):
varname = ctx.visitor.varname_for_self_constraint(ctx.node)
if varname is not None:
no_return_unless = Constraint(
varname,
ConstraintType.is_value_object,
True,
SequenceValue.make_or_known(list, (*lst.members, (False, element))),
)
return ImplReturn(KnownValue(None), no_return_unless=no_return_unless)
elif isinstance(lst, GenericValue):
return _check_generic_container(
"list.append", "object", ctx.vars["self"], lst, element, ctx, list
)
if isinstance(lst, GenericValue):
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This could alternatively be elif, which would allow us to append anything to a SequenceValue (i.e., unannotated) list. But I just ran this branch internally and only got three errors, all of which were fixable by adding explicit annotations. I think such annotations are helpful, so I'll stick with this logic.

return _check_generic_container(
"list.append", "object", ctx.vars["self"], lst, element, ctx, list
)
return ImplReturn(KnownValue(None))


Expand Down Expand Up @@ -999,11 +999,7 @@ def inner(lst: Value, iterable: Value) -> ImplReturn:
varname, ConstraintType.is_value_object, True, constrained_value
)
return ImplReturn(KnownValue(None), no_return_unless=no_return_unless)
elif (
varname is not None
and isinstance(cleaned_lst, GenericValue)
and isinstance(iterable, TypedValue)
):
if isinstance(cleaned_lst, GenericValue) and isinstance(iterable, TypedValue):
actual_type = iterable.get_generic_arg_for_type(
collections.abc.Iterable, ctx.visitor, 0
)
Expand Down Expand Up @@ -1058,9 +1054,9 @@ def _check_generic_container(
def _set_add_impl(ctx: CallContext) -> ImplReturn:
set_value = replace_known_sequence_value(ctx.vars["self"])
element = ctx.vars["object"]
varname = ctx.visitor.varname_for_self_constraint(ctx.node)
if varname is not None:
if isinstance(set_value, SequenceValue):
if isinstance(set_value, SequenceValue):
varname = ctx.visitor.varname_for_self_constraint(ctx.node)
if varname is not None:
no_return_unless = Constraint(
varname,
ConstraintType.is_value_object,
Expand All @@ -1070,10 +1066,10 @@ def _set_add_impl(ctx: CallContext) -> ImplReturn:
),
)
return ImplReturn(KnownValue(None), no_return_unless=no_return_unless)
elif isinstance(set_value, GenericValue):
return _check_generic_container(
"set.add", "object", ctx.vars["self"], set_value, element, ctx, set
)
if isinstance(set_value, GenericValue):
return _check_generic_container(
"set.add", "object", ctx.vars["self"], set_value, element, ctx, set
)
return ImplReturn(KnownValue(None))


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2 changes: 1 addition & 1 deletion pyanalyze/node_visitor.py
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Expand Up @@ -167,7 +167,7 @@ class BaseNodeVisitor(ast.NodeVisitor):
should_check_environ_for_files: bool = True
caught_errors: Optional[List[Dict[str, Any]]] = None

_changes_for_fixer = collections.defaultdict(list)
_changes_for_fixer: Dict[str, List[Replacement]] = collections.defaultdict(list)

tree: ast.Module
all_failures: List[Failure]
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6 changes: 6 additions & 0 deletions pyanalyze/test_implementation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -419,6 +419,12 @@ def capybara():
assert_is_value(lst, GenericValue(list, [TypedValue(str)]))
lst.append(1) # E: incompatible_argument

double_lst: List[List[int]] = [[42]]
assert_is_value(
double_lst, GenericValue(list, [GenericValue(list, [TypedValue(int)])])
)
double_lst[0].append("x") # E: incompatible_argument

@assert_passes()
def test_set_add(self):
from typing import Set
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