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[ty] Emit diagnostics for invalid dynamic namedtuple fields

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This commit is contained in:
Charlie Marsh
2026-01-14 11:03:58 -05:00
parent c3909525c6
commit 1bfdfafecf
2 changed files with 95 additions and 15 deletions
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25
crates/ty_python_semantic/resources/mdtest/named_tuple.md
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@@ -466,6 +466,27 @@ Point2 = collections.namedtuple("Point2", ["_x", "class"], rename=1)
reveal_type(Point2) # revealed: <class 'Point2'>
reveal_type(Point2.__new__) # revealed: (cls: type, _0: Any, _1: Any) -> Point2
# Without `rename=True`, invalid field names emit diagnostics:
# - Field names starting with underscore
# error: [invalid-named-tuple] "Field name `_x` in `namedtuple()` cannot start with an underscore"
Underscore = collections.namedtuple("Underscore", ["_x", "y"])
reveal_type(Underscore) # revealed: <class 'Underscore'>
# - Python keywords
# error: [invalid-named-tuple] "Field name `class` in `namedtuple()` cannot be a Python keyword"
Keyword = collections.namedtuple("Keyword", ["x", "class"])
reveal_type(Keyword) # revealed: <class 'Keyword'>
# - Duplicate field names
# error: [invalid-named-tuple] "Duplicate field name `x` in `namedtuple()`"
Duplicate = collections.namedtuple("Duplicate", ["x", "y", "x"])
reveal_type(Duplicate) # revealed: <class 'Duplicate'>
# - Invalid identifiers (e.g., containing spaces)
# error: [invalid-named-tuple] "Field name `not valid` in `namedtuple()` is not a valid identifier"
Invalid = collections.namedtuple("Invalid", ["not valid", "ok"])
reveal_type(Invalid) # revealed: <class 'Invalid'>
# `defaults` provides default values for the rightmost fields
Person = collections.namedtuple("Person", ["name", "age", "city"], defaults=["Unknown"])
reveal_type(Person) # revealed: <class 'Person'>
@@ -483,8 +504,8 @@ reveal_type(person2.city) # revealed: Any
Config = collections.namedtuple("Config", ["host", "port"], module="myapp")
reveal_type(Config) # revealed: <class 'Config'>
# When more defaults are provided than fields, we treat all fields as having defaults.
# TODO: This should emit a diagnostic since it would fail at runtime.
# When more defaults are provided than fields, an error is emitted.
# error: [invalid-named-tuple] "Too many defaults for `namedtuple()`"
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 = "a", y: Any = "b") -> TooManyDefaults