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[red-knot] Detect (some) invalid protocols (#17488)
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Alex Waygood
GitHub
parent
9ff4772a2c
commit
45b5dedee2
4 changed files with 76 additions and 19 deletions
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@ -136,13 +136,13 @@ If `Protocol` is present in the bases tuple, all other bases in the tuple must b
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or `TypeError` is raised at runtime when the class is created.
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```py
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# TODO: should emit `[invalid-protocol]`
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# error: [invalid-protocol] "Protocol class `Invalid` cannot inherit from non-protocol class `NotAProtocol`"
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class Invalid(NotAProtocol, Protocol): ...
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# revealed: tuple[Literal[Invalid], Literal[NotAProtocol], typing.Protocol, typing.Generic, Literal[object]]
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reveal_type(Invalid.__mro__)
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# TODO: should emit an `[invalid-protocol`] error
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# error: [invalid-protocol] "Protocol class `AlsoInvalid` cannot inherit from non-protocol class `NotAProtocol`"
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class AlsoInvalid(MyProtocol, OtherProtocol, NotAProtocol, Protocol): ...
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# revealed: tuple[Literal[AlsoInvalid], Literal[MyProtocol], Literal[OtherProtocol], Literal[NotAProtocol], typing.Protocol, typing.Generic, Literal[object]]
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@ -36,6 +36,7 @@ pub(crate) fn register_lints(registry: &mut LintRegistryBuilder) {
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registry.register_lint(&INVALID_EXCEPTION_CAUGHT);
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registry.register_lint(&INVALID_METACLASS);
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registry.register_lint(&INVALID_PARAMETER_DEFAULT);
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registry.register_lint(&INVALID_PROTOCOL);
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registry.register_lint(&INVALID_RAISE);
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registry.register_lint(&INVALID_SUPER_ARGUMENT);
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registry.register_lint(&INVALID_TYPE_CHECKING_CONSTANT);
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@ -230,6 +231,34 @@ declare_lint! {
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}
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}
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declare_lint! {
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/// ## What it does
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/// Checks for invalidly defined protocol classes.
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///
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/// ## Why is this bad?
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/// An invalidly defined protocol class may lead to the type checker inferring
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/// unexpected things. It may also lead to `TypeError`s at runtime.
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///
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/// ## Examples
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/// A `Protocol` class cannot inherit from a non-`Protocol` class;
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/// this raises a `TypeError` at runtime:
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///
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/// ```pycon
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/// >>> from typing import Protocol
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/// >>> class Foo(int, Protocol): ...
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/// ...
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/// Traceback (most recent call last):
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/// File "<python-input-1>", line 1, in <module>
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/// class Foo(int, Protocol): ...
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/// TypeError: Protocols can only inherit from other protocols, got <class 'int'>
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/// ```
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pub(crate) static INVALID_PROTOCOL = {
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summary: "detects invalid protocol class definitions",
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status: LintStatus::preview("1.0.0"),
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default_level: Level::Error,
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}
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}
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declare_lint! {
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/// TODO #14889
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pub(crate) static INCONSISTENT_MRO = {
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@ -99,8 +99,8 @@ use super::diagnostic::{
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report_index_out_of_bounds, report_invalid_exception_caught, report_invalid_exception_cause,
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report_invalid_exception_raised, report_invalid_type_checking_constant,
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report_non_subscriptable, report_possibly_unresolved_reference, report_slice_step_size_zero,
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report_unresolved_reference, INVALID_METACLASS, REDUNDANT_CAST, STATIC_ASSERT_ERROR,
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SUBCLASS_OF_FINAL_CLASS, TYPE_ASSERTION_FAILURE,
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report_unresolved_reference, INVALID_METACLASS, INVALID_PROTOCOL, REDUNDANT_CAST,
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STATIC_ASSERT_ERROR, SUBCLASS_OF_FINAL_CLASS, TYPE_ASSERTION_FAILURE,
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};
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use super::slots::check_class_slots;
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use super::string_annotation::{
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@ -763,17 +763,21 @@ impl<'db> TypeInferenceBuilder<'db> {
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continue;
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}
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// (2) Check for inheritance from plain `Generic`,
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// and from classes that inherit from `@final` classes
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let is_protocol = class.is_protocol(self.db());
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// (2) Iterate through the class's explicit bases to check for various possible errors:
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// - Check for inheritance from plain `Generic`,
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// - Check for inheritance from a `@final` classes
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// - If the class is a protocol class: check for inheritance from a non-protocol class
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for (i, base_class) in class.explicit_bases(self.db()).iter().enumerate() {
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let base_class = match base_class {
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Type::KnownInstance(KnownInstanceType::Generic) => {
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// `Generic` can appear in the MRO of many classes,
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// Unsubscripted `Generic` can appear in the MRO of many classes,
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// but it is never valid as an explicit base class in user code.
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self.context.report_lint_old(
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&INVALID_BASE,
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&class_node.bases()[i],
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format_args!("Cannot inherit from plain `Generic`",),
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format_args!("Cannot inherit from plain `Generic`"),
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);
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continue;
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}
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@ -782,9 +786,22 @@ impl<'db> TypeInferenceBuilder<'db> {
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_ => continue,
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};
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if !base_class.is_final(self.db()) {
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continue;
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if is_protocol
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&& !(base_class.is_protocol(self.db())
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|| base_class.is_known(self.db(), KnownClass::Object))
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{
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self.context.report_lint_old(
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&INVALID_PROTOCOL,
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&class_node.bases()[i],
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format_args!(
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"Protocol class `{}` cannot inherit from non-protocol class `{}`",
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class.name(self.db()),
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base_class.name(self.db()),
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),
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);
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}
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if base_class.is_final(self.db()) {
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self.context.report_lint_old(
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&SUBCLASS_OF_FINAL_CLASS,
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&class_node.bases()[i],
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@ -795,6 +812,7 @@ impl<'db> TypeInferenceBuilder<'db> {
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),
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);
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}
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}
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// (3) Check that the class's MRO is resolvable
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match class.try_mro(self.db(), None).as_ref() {
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@ -460,6 +460,16 @@
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}
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]
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},
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"invalid-protocol": {
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"title": "detects invalid protocol class definitions",
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"description": "## What it does\nChecks for invalidly defined protocol classes.\n\n## Why is this bad?\nAn invalidly defined protocol class may lead to the type checker inferring\nunexpected things. It may also lead to `TypeError`s at runtime.\n\n## Examples\nA `Protocol` class cannot inherit from a non-`Protocol` class;\nthis raises a `TypeError` at runtime:\n\n```pycon\n>>> from typing import Protocol\n>>> class Foo(int, Protocol): ...\n...\nTraceback (most recent call last):\n File \"<python-input-1>\", line 1, in <module>\n class Foo(int, Protocol): ...\nTypeError: Protocols can only inherit from other protocols, got <class 'int'>\n```",
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"default": "error",
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"oneOf": [
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{
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"$ref": "#/definitions/Level"
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}
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]
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},
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"invalid-raise": {
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"title": "detects `raise` statements that raise invalid exceptions or use invalid causes",
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"description": "Checks for `raise` statements that raise non-exceptions or use invalid\ncauses for their raised exceptions.\n\n## Why is this bad?\nOnly subclasses or instances of `BaseException` can be raised.\nFor an exception's cause, the same rules apply, except that `None` is also\npermitted. Violating these rules results in a `TypeError` at runtime.\n\n## Examples\n```python\ndef f():\n try:\n something()\n except NameError:\n raise \"oops!\" from f\n\ndef g():\n raise NotImplemented from 42\n```\n\nUse instead:\n```python\ndef f():\n try:\n something()\n except NameError as e:\n raise RuntimeError(\"oops!\") from e\n\ndef g():\n raise NotImplementedError from None\n```\n\n## References\n- [Python documentation: The `raise` statement](https://docs.python.org/3/reference/simple_stmts.html#raise)\n- [Python documentation: Built-in Exceptions](https://docs.python.org/3/library/exceptions.html#built-in-exceptions)",
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