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[ty] Show dynamic NamedTuple defaults in signature (#22574)

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## Summary

Follow-up from https://github.com/astral-sh/ruff/pull/22327.
This commit is contained in:
Charlie Marsh
2026-01-14 13:28:23 -05:00
committed by GitHub
parent eaed0d9b5c
commit 87eec9bb51
2 changed files with 45 additions and 12 deletions
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5
crates/ty_python_semantic/resources/mdtest/named_tuple.md
View File

@@ -469,7 +469,8 @@ reveal_type(Point2.__new__) # revealed: (cls: type, _0: Any, _1: Any) -> Point2
# `defaults` provides default values for the rightmost fields
Person = collections.namedtuple("Person", ["name", "age", "city"], defaults=["Unknown"])
reveal_type(Person) # revealed: <class 'Person'>
reveal_type(Person.__new__) # revealed: (cls: type, name: Any, age: Any, city: Any = ...) -> Person
reveal_type(Person.__new__) # revealed: (cls: type, name: Any, age: Any, city: Any = "Unknown") -> Person
reveal_mro(Person) # revealed: (<class 'Person'>, <class 'tuple[Any, Any, Any]'>, <class 'object'>)
# Can create with all fields
person1 = Person("Alice", 30, "NYC")
@@ -486,7 +487,7 @@ reveal_type(Config) # revealed: <class 'Config'>
# TODO: This should emit a diagnostic since it would fail at runtime.
TooManyDefaults = collections.namedtuple("TooManyDefaults", ["x", "y"], defaults=("a", "b", "c"))
reveal_type(TooManyDefaults) # revealed: <class 'TooManyDefaults'>
reveal_type(TooManyDefaults.__new__) # revealed: (cls: type, x: Any = ..., y: Any = ...) -> TooManyDefaults
reveal_type(TooManyDefaults.__new__) # revealed: (cls: type, x: Any = "a", y: Any = "b") -> TooManyDefaults
# Unknown keyword arguments produce an error
# error: [unknown-argument]

52
crates/ty_python_semantic/src/types/infer/builder.rs
View File

@@ -6564,7 +6564,7 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
}
// Infer keyword arguments.
let mut defaults_count = None;
let mut default_types: Vec<Type<'db>> = vec![];
let mut rename_type = None;
for kw in keywords {
@@ -6575,11 +6575,42 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
};
match arg.id.as_str() {
"defaults" if kind.is_collections() => {
defaults_count = kw_type
.exact_tuple_instance_spec(db)
.and_then(|spec| spec.len().maximum())
.or_else(|| kw.value.as_list_expr().map(|list| list.elts.len()));
// Extract element types from AST literals (using already-inferred types)
// or fall back to the inferred tuple spec.
match &kw.value {
ast::Expr::List(list) => {
// Elements were already inferred when we inferred kw.value above.
default_types = list
.elts
.iter()
.map(|elt| self.expression_type(elt))
.collect();
}
ast::Expr::Tuple(tuple) => {
// Elements were already inferred when we inferred kw.value above.
default_types = tuple
.elts
.iter()
.map(|elt| self.expression_type(elt))
.collect();
}
_ => {
// Fall back to using the already-inferred type.
// Try to extract element types from tuple.
if let Some(spec) = kw_type.exact_tuple_instance_spec(db)
&& let Some(fixed) = spec.as_fixed_length()
{
default_types = fixed.all_elements().to_vec();
} else {
// Can't determine individual types; use Any for each element.
let count = kw_type
.exact_tuple_instance_spec(db)
.and_then(|spec| spec.len().maximum())
.unwrap_or(0);
default_types = vec![Type::any(); count];
}
}
}
// Emit diagnostic for invalid types (not Iterable[Any] | None).
let iterable_any =
KnownClass::Iterable.to_specialized_instance(db, &[Type::any()]);
@@ -6644,8 +6675,6 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
}
}
let defaults_count = defaults_count.unwrap_or_default();
// Extract name.
let name = if let Type::StringLiteral(literal) = name_type {
Name::new(literal.value(db))
@@ -6778,14 +6807,17 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
// TODO: emit a diagnostic when `defaults_count > num_fields` (which would
// fail at runtime with `TypeError: Got more default values than field names`).
let num_fields = field_names.len();
let defaults_count = defaults_count.min(num_fields);
let defaults_count = default_types.len().min(num_fields);
let fields = field_names
.iter()
.enumerate()
.map(|(i, field_name)| {
let default =
if defaults_count > 0 && i >= num_fields - defaults_count {
Some(Type::any())
// Index into default_types: first default corresponds to first
// field that has a default.
let default_idx = i - (num_fields - defaults_count);
Some(default_types[default_idx])
} else {
None
};