Implement flake8-future-annotations FA100 (#3979)

README.md

@@ -263,6 +263,7 @@ quality tools, including:
 - [flake8-eradicate](https://pypi.org/project/flake8-eradicate/)
 - [flake8-errmsg](https://pypi.org/project/flake8-errmsg/)
 - [flake8-executable](https://pypi.org/project/flake8-executable/)
+- [flake8-future-annotations](https://pypi.org/project/flake8-future-annotations/)
 - [flake8-gettext](https://pypi.org/project/flake8-gettext/)
 - [flake8-implicit-str-concat](https://pypi.org/project/flake8-implicit-str-concat/)
 - [flake8-import-conventions](https://github.com/joaopalmeiro/flake8-import-conventions)

crates/ruff/resources/test/fixtures/flake8_future_annotations/edge_case.py

@@ -0,0 +1,7 @@
+from typing import List
+import typing as t
+
+
+def main(_: List[int]) -> None:
+    a_list: t.List[str] = []
+    a_list.append("hello")

crates/ruff/resources/test/fixtures/flake8_future_annotations/from_typing_import.py

@@ -0,0 +1,6 @@
+from typing import List
+
+
+def main() -> None:
+    a_list: List[str] = []
+    a_list.append("hello")

crates/ruff/resources/test/fixtures/flake8_future_annotations/from_typing_import_many.py

@@ -0,0 +1,8 @@
+from typing import Dict, List, Optional, Set, Union, cast
+
+
+def main() -> None:
+    a_list: List[Optional[str]] = []
+    a_list.append("hello")
+    a_dict = cast(Dict[int | None, Union[int, Set[bool]]], {})
+    a_dict[1] = {True, False}

crates/ruff/resources/test/fixtures/flake8_future_annotations/import_typing.py

@@ -0,0 +1,6 @@
+import typing
+
+
+def main() -> None:
+    a_list: typing.List[str] = []
+    a_list.append("hello")

crates/ruff/resources/test/fixtures/flake8_future_annotations/import_typing_as.py

@@ -0,0 +1,6 @@
+import typing as t
+
+
+def main() -> None:
+    a_list: t.List[str] = []
+    a_list.append("hello")

crates/ruff/resources/test/fixtures/flake8_future_annotations/no_future_import_uses_lowercase.py

@@ -0,0 +1,7 @@
+def main() -> None:
+    a_list: list[str] = []
+    a_list.append("hello")
+
+
+def hello(y: dict[str, int]) -> None:
+    del y

crates/ruff/resources/test/fixtures/flake8_future_annotations/no_future_import_uses_union.py

@@ -0,0 +1,7 @@
+def main() -> None:
+    a_list: list[str] | None = []
+    a_list.append("hello")
+
+
+def hello(y: dict[str, int] | None) -> None:
+    del y

crates/ruff/resources/test/fixtures/flake8_future_annotations/no_future_import_uses_union_inner.py

@@ -0,0 +1,8 @@
+def main() -> None:
+    a_list: list[str | None] = []
+    a_list.append("hello")
+
+
+def hello(y: dict[str | None, int]) -> None:
+    z: tuple[str, str | None, str] = tuple(y)
+    del z

crates/ruff/resources/test/fixtures/flake8_future_annotations/ok_no_types.py

@@ -0,0 +1,3 @@
+def main() -> str:
+    a_str = "hello"
+    return a_str

crates/ruff/resources/test/fixtures/flake8_future_annotations/ok_non_simplifiable_types.py

@@ -0,0 +1,10 @@
+from typing import NamedTuple
+
+
+class Stuff(NamedTuple):
+    x: int
+
+
+def main() -> None:
+    a_list = Stuff(5)
+    print(a_list)

crates/ruff/resources/test/fixtures/flake8_future_annotations/ok_uses_future.py

@@ -0,0 +1,6 @@
+from __future__ import annotations
+
+
+def main() -> None:
+    a_list: list[str] = []
+    a_list.append("hello")

crates/ruff/resources/test/fixtures/flake8_future_annotations/ok_variable_name.py

@@ -0,0 +1,8 @@
+import typing
+
+IRRELEVANT = typing.TypeVar
+
+
+def main() -> None:
+    List: list[str] = []
+    List.append("hello")

crates/ruff/src/checkers/ast/mod.rs

@@ -44,12 +44,12 @@ use crate::registry::{AsRule, Rule};
 use crate::rules::{
     flake8_2020, flake8_annotations, flake8_bandit, flake8_blind_except, flake8_boolean_trap,
     flake8_bugbear, flake8_builtins, flake8_comprehensions, flake8_datetimez, flake8_debugger,
-    flake8_django, flake8_errmsg, flake8_gettext, flake8_implicit_str_concat,
-    flake8_import_conventions, flake8_logging_format, flake8_pie, flake8_print, flake8_pyi,
-    flake8_pytest_style, flake8_raise, flake8_return, flake8_self, flake8_simplify,
-    flake8_tidy_imports, flake8_type_checking, flake8_unused_arguments, flake8_use_pathlib, flynt,
-    mccabe, numpy, pandas_vet, pep8_naming, pycodestyle, pydocstyle, pyflakes, pygrep_hooks,
-    pylint, pyupgrade, ruff, tryceratops,
+    flake8_django, flake8_errmsg, flake8_future_annotations, flake8_gettext,
+    flake8_implicit_str_concat, flake8_import_conventions, flake8_logging_format, flake8_pie,
+    flake8_print, flake8_pyi, flake8_pytest_style, flake8_raise, flake8_return, flake8_self,
+    flake8_simplify, flake8_tidy_imports, flake8_type_checking, flake8_unused_arguments,
+    flake8_use_pathlib, flynt, mccabe, numpy, pandas_vet, pep8_naming, pycodestyle, pydocstyle,
+    pyflakes, pygrep_hooks, pylint, pyupgrade, ruff, tryceratops,
 };
 use crate::settings::types::PythonVersion;
 use crate::settings::{flags, Settings};
@@ -1077,7 +1077,6 @@ where
                         pyupgrade::rules::unnecessary_builtin_import(self, stmt, module, names);
                     }
                 }
-
                 if self.settings.rules.enabled(Rule::BannedApi) {
                     if let Some(module) =
                         helpers::resolve_imported_module_path(level, module, self.module_path)
@@ -2258,12 +2257,25 @@ where
         match &expr.node {
             ExprKind::Subscript(ast::ExprSubscript { value, slice, .. }) => {
                 // Ex) Optional[...], Union[...]
+                if self
+                    .settings
+                    .rules
+                    .enabled(Rule::MissingFutureAnnotationsImport)
+                    && (self.settings.target_version < PythonVersion::Py310
+                        && (self.settings.target_version >= PythonVersion::Py37
+                            && !self.ctx.future_annotations()
+                            && self.ctx.in_annotation()))
+                    && analyze::typing::is_pep604_builtin(value, &self.ctx)
+                {
+                    flake8_future_annotations::rules::missing_future_annotations(self, value);
+                }
                 if !self.settings.pyupgrade.keep_runtime_typing
                     && self.settings.rules.enabled(Rule::NonPEP604Annotation)
                     && (self.settings.target_version >= PythonVersion::Py310
                         || (self.settings.target_version >= PythonVersion::Py37
                             && self.ctx.future_annotations()
                             && self.ctx.in_annotation()))
+                    && analyze::typing::is_pep604_builtin(value, &self.ctx)
                 {
                     pyupgrade::rules::use_pep604_annotation(self, expr, value, slice);
                 }
@@ -2321,6 +2333,20 @@ where
                         }
 
                         // Ex) List[...]
+                        if self
+                            .settings
+                            .rules
+                            .enabled(Rule::MissingFutureAnnotationsImport)
+                            && (self.settings.target_version < PythonVersion::Py39
+                                && (self.settings.target_version >= PythonVersion::Py37
+                                    && !self.ctx.future_annotations()
+                                    && self.ctx.in_annotation()))
+                            && analyze::typing::is_pep585_builtin(expr, &self.ctx)
+                        {
+                            flake8_future_annotations::rules::missing_future_annotations(
+                                self, expr,
+                            );
+                        }
                         if !self.settings.pyupgrade.keep_runtime_typing
                             && self.settings.rules.enabled(Rule::NonPEP585Annotation)
                             && (self.settings.target_version >= PythonVersion::Py39
@@ -2372,6 +2398,18 @@ where
             }
             ExprKind::Attribute(ast::ExprAttribute { attr, value, .. }) => {
                 // Ex) typing.List[...]
+                if self
+                    .settings
+                    .rules
+                    .enabled(Rule::MissingFutureAnnotationsImport)
+                    && (self.settings.target_version < PythonVersion::Py39
+                        && (self.settings.target_version >= PythonVersion::Py37
+                            && !self.ctx.future_annotations()
+                            && self.ctx.in_annotation()))
+                    && analyze::typing::is_pep585_builtin(expr, &self.ctx)
+                {
+                    flake8_future_annotations::rules::missing_future_annotations(self, expr);
+                }
                 if !self.settings.pyupgrade.keep_runtime_typing
                     && self.settings.rules.enabled(Rule::NonPEP585Annotation)
                     && (self.settings.target_version >= PythonVersion::Py39

crates/ruff/src/codes.rs

@@ -331,6 +331,9 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<Rule> {
         (Flake8Annotations, "206") => Rule::MissingReturnTypeClassMethod,
         (Flake8Annotations, "401") => Rule::AnyType,
 
+        // flake8-future-annotations
+        (Flake8FutureAnnotations, "100") => Rule::MissingFutureAnnotationsImport,
+
         // flake8-2020
         (Flake82020, "101") => Rule::SysVersionSlice3,
         (Flake82020, "102") => Rule::SysVersion2,

crates/ruff/src/registry.rs

@@ -290,6 +290,8 @@ ruff_macros::register_rules!(
     rules::flake8_annotations::rules::MissingReturnTypeStaticMethod,
     rules::flake8_annotations::rules::MissingReturnTypeClassMethod,
     rules::flake8_annotations::rules::AnyType,
+    // flake8-future-annotations
+    rules::flake8_future_annotations::rules::MissingFutureAnnotationsImport,
     // flake8-2020
     rules::flake8_2020::rules::SysVersionSlice3,
     rules::flake8_2020::rules::SysVersion2,
@@ -769,6 +771,9 @@ pub enum Linter {
     /// [flake8-executable](https://pypi.org/project/flake8-executable/)
     #[prefix = "EXE"]
     Flake8Executable,
+    /// [flake8-future-annotations](https://pypi.org/project/flake8-future-annotations/)
+    #[prefix = "FA"]
+    Flake8FutureAnnotations,
     /// [flake8-implicit-str-concat](https://pypi.org/project/flake8-implicit-str-concat/)
     #[prefix = "ISC"]
     Flake8ImplicitStrConcat,

crates/ruff/src/rules/flake8_future_annotations/mod.rs

@@ -0,0 +1,40 @@
+//! Rules from [flake8-future-annotations](https://pypi.org/project/flake8-future-annotations/).
+pub(crate) mod rules;
+
+#[cfg(test)]
+mod tests {
+    use std::path::Path;
+
+    use anyhow::Result;
+    use test_case::test_case;
+
+    use crate::registry::Rule;
+    use crate::settings::types::PythonVersion;
+    use crate::test::test_path;
+    use crate::{assert_messages, settings};
+
+    #[test_case(Path::new("edge_case.py"); "edge_case")]
+    #[test_case(Path::new("from_typing_import.py"); "from_typing_import")]
+    #[test_case(Path::new("from_typing_import_many.py"); "from_typing_import_many")]
+    #[test_case(Path::new("import_typing.py"); "import_typing")]
+    #[test_case(Path::new("import_typing_as.py"); "import_typing_as")]
+    #[test_case(Path::new("no_future_import_uses_lowercase.py"); "no_future_import_uses_lowercase")]
+    #[test_case(Path::new("no_future_import_uses_union.py"); "no_future_import_uses_union")]
+    #[test_case(Path::new("no_future_import_uses_union_inner.py"); "no_future_import_uses_union_inner")]
+    #[test_case(Path::new("ok_no_types.py"); "ok_no_types")]
+    #[test_case(Path::new("ok_non_simplifiable_types.py"); "ok_non_simplifiable_types")]
+    #[test_case(Path::new("ok_uses_future.py"); "ok_uses_future")]
+    #[test_case(Path::new("ok_variable_name.py"); "ok_variable_name")]
+    fn rules(path: &Path) -> Result<()> {
+        let snapshot = path.to_string_lossy().into_owned();
+        let diagnostics = test_path(
+            Path::new("flake8_future_annotations").join(path).as_path(),
+            &settings::Settings {
+                target_version: PythonVersion::Py37,
+                ..settings::Settings::for_rule(Rule::MissingFutureAnnotationsImport)
+            },
+        )?;
+        assert_messages!(snapshot, diagnostics);
+        Ok(())
+    }
+}

crates/ruff/src/rules/flake8_future_annotations/rules.rs

@@ -0,0 +1,78 @@
+use rustpython_parser::ast::Expr;
+
+use ruff_diagnostics::{Diagnostic, Violation};
+use ruff_macros::{derive_message_formats, violation};
+use ruff_python_ast::call_path::format_call_path;
+
+use crate::checkers::ast::Checker;
+
+/// ## What it does
+/// Checks for missing `from __future__ import annotations` imports upon
+/// detecting type annotations that can be written more succinctly under
+/// PEP 563.
+///
+/// ## Why is this bad?
+/// PEP 563 enabled the use of a number of convenient type annotations, such as
+/// `list[str]` instead of `List[str]`, or `str | None` instead of
+/// `Optional[str]`. However, these annotations are only available on Python
+/// 3.9 and higher, _unless_ the `from __future__ import annotations` import is present.
+///
+/// By adding the `__future__` import, the pyupgrade rules can automatically
+/// migrate existing code to use the new syntax, even for older Python versions.
+/// This rule thus pairs well with pyupgrade and with Ruff's pyupgrade rules.
+///
+/// ## Example
+/// ```python
+/// from typing import List, Dict, Optional
+///
+///
+/// def function(a_dict: Dict[str, Optional[int]]) -> None:
+///     a_list: List[str] = []
+///     a_list.append("hello")
+/// ```
+///
+/// Use instead:
+/// ```python
+/// from __future__ import annotations
+///
+/// from typing import List, Dict, Optional
+///
+///
+/// def function(a_dict: Dict[str, Optional[int]]) -> None:
+///     a_list: List[str] = []
+///     a_list.append("hello")
+/// ```
+///
+/// After running the additional pyupgrade rules:
+/// ```python
+/// from __future__ import annotations
+///
+///
+/// def function(a_dict: dict[str, int | None]) -> None:
+///     a_list: list[str] = []
+///     a_list.append("hello")
+/// ```
+#[violation]
+pub struct MissingFutureAnnotationsImport {
+    name: String,
+}
+
+impl Violation for MissingFutureAnnotationsImport {
+    #[derive_message_formats]
+    fn message(&self) -> String {
+        let MissingFutureAnnotationsImport { name } = self;
+        format!("Missing `from __future__ import annotations`, but uses `{name}`")
+    }
+}
+
+/// FA100
+pub(crate) fn missing_future_annotations(checker: &mut Checker, expr: &Expr) {
+    if let Some(binding) = checker.ctx.resolve_call_path(expr) {
+        checker.diagnostics.push(Diagnostic::new(
+            MissingFutureAnnotationsImport {
+                name: format_call_path(&binding),
+            },
+            expr.range(),
+        ));
+    }
+}

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__edge_case.py.snap

@@ -0,0 +1,12 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+edge_case.py:6:13: FA100 Missing `from __future__ import annotations`, but uses `typing.List`
+  |
+6 | def main(_: List[int]) -> None:
+7 |     a_list: t.List[str] = []
+  |             ^^^^^^ FA100
+8 |     a_list.append("hello")
+  |
+
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__from_typing_import.py.snap

@@ -0,0 +1,12 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+from_typing_import.py:5:13: FA100 Missing `from __future__ import annotations`, but uses `typing.List`
+  |
+5 | def main() -> None:
+6 |     a_list: List[str] = []
+  |             ^^^^ FA100
+7 |     a_list.append("hello")
+  |
+
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__from_typing_import_many.py.snap

@@ -0,0 +1,22 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+from_typing_import_many.py:5:13: FA100 Missing `from __future__ import annotations`, but uses `typing.List`
+  |
+5 | def main() -> None:
+6 |     a_list: List[Optional[str]] = []
+  |             ^^^^ FA100
+7 |     a_list.append("hello")
+8 |     a_dict = cast(Dict[int | None, Union[int, Set[bool]]], {})
+  |
+
+from_typing_import_many.py:5:18: FA100 Missing `from __future__ import annotations`, but uses `typing.Optional`
+  |
+5 | def main() -> None:
+6 |     a_list: List[Optional[str]] = []
+  |                  ^^^^^^^^ FA100
+7 |     a_list.append("hello")
+8 |     a_dict = cast(Dict[int | None, Union[int, Set[bool]]], {})
+  |
+
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__import_typing.py.snap

@@ -0,0 +1,12 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+import_typing.py:5:13: FA100 Missing `from __future__ import annotations`, but uses `typing.List`
+  |
+5 | def main() -> None:
+6 |     a_list: typing.List[str] = []
+  |             ^^^^^^^^^^^ FA100
+7 |     a_list.append("hello")
+  |
+
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__import_typing_as.py.snap

@@ -0,0 +1,12 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+import_typing_as.py:5:13: FA100 Missing `from __future__ import annotations`, but uses `typing.List`
+  |
+5 | def main() -> None:
+6 |     a_list: t.List[str] = []
+  |             ^^^^^^ FA100
+7 |     a_list.append("hello")
+  |
+
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__no_future_import_uses_lowercase.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__no_future_import_uses_union.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__no_future_import_uses_union_inner.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__ok_no_types.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__ok_non_simplifiable_types.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__ok_uses_future.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+

crates/ruff/src/rules/flake8_future_annotations/snapshots/ruff__rules__flake8_future_annotations__tests__ok_variable_name.py.snap

@@ -0,0 +1,4 @@
+---
+source: crates/ruff/src/rules/flake8_future_annotations/mod.rs
+---
+

crates/ruff/src/rules/mod.rs

@@ -14,6 +14,7 @@ pub mod flake8_debugger;
 pub mod flake8_django;
 pub mod flake8_errmsg;
 pub mod flake8_executable;
+pub mod flake8_future_annotations;
 pub mod flake8_gettext;
 pub mod flake8_implicit_str_concat;
 pub mod flake8_import_conventions;

crates/ruff_python_semantic/src/analyze/typing.rs

@@ -70,6 +70,15 @@ pub fn is_pep585_builtin(expr: &Expr, context: &Context) -> bool {
     })
 }
 
+/// Returns `true` if `Expr` represents a reference to a typing object with a
+/// PEP 603 built-in.
+pub fn is_pep604_builtin(expr: &Expr, context: &Context) -> bool {
+    context.resolve_call_path(expr).map_or(false, |call_path| {
+        context.match_typing_call_path(&call_path, "Optional")
+            || context.match_typing_call_path(&call_path, "Union")
+    })
+}
+
 pub fn is_immutable_annotation(context: &Context, expr: &Expr) -> bool {
     match &expr.node {
         ExprKind::Name(_) | ExprKind::Attribute(_) => {

ruff.schema.json

@@ -1816,6 +1816,10 @@
         "F9",
         "F90",
         "F901",
+        "FA",
+        "FA1",
+        "FA10",
+        "FA100",
         "FBT",
         "FBT0",
         "FBT00",

scripts/check_ecosystem.py

@@ -5,6 +5,7 @@ Example usage:
 
     scripts/check_ecosystem.py <path/to/ruff1> <path/to/ruff2>
 """
+from __future__ import annotations
 
 import argparse
 import asyncio
@@ -18,7 +19,7 @@ import time
 from asyncio.subprocess import PIPE, create_subprocess_exec
 from contextlib import asynccontextmanager, nullcontext
 from pathlib import Path
-from typing import TYPE_CHECKING, NamedTuple, Optional, Self
+from typing import TYPE_CHECKING, NamedTuple, Self
 
 if TYPE_CHECKING:
     from collections.abc import AsyncIterator, Iterator, Sequence
@@ -31,13 +32,13 @@ class Repository(NamedTuple):
 
     org: str
     repo: str
-    ref: Optional[str]
+    ref: str | None
     select: str = ""
     ignore: str = ""
     exclude: str = ""
 
     @asynccontextmanager
-    async def clone(self: Self, checkout_dir: Path) -> "AsyncIterator[Path]":
+    async def clone(self: Self, checkout_dir: Path) -> AsyncIterator[Path]:
         """Shallow clone this repository to a temporary directory."""
         if checkout_dir.exists():
             logger.debug(f"Reusing {self.org}/{self.repo}")
@@ -101,7 +102,7 @@ async def check(
     select: str = "",
     ignore: str = "",
     exclude: str = "",
-) -> "Sequence[str]":
+) -> Sequence[str]:
     """Run the given ruff binary against the specified path."""
     logger.debug(f"Checking {name} with {ruff}")
     ruff_args = ["check", "--no-cache", "--exit-zero"]
@@ -148,7 +149,7 @@ class Diff(NamedTuple):
         """Return true if this diff is non-empty."""
         return bool(self.removed or self.added)
 
-    def __iter__(self: Self) -> "Iterator[str]":
+    def __iter__(self: Self) -> Iterator[str]:
         """Iterate through the changed lines in diff format."""
         for line in heapq.merge(sorted(self.removed), sorted(self.added)):
             if line in self.removed:
@@ -161,7 +162,7 @@ async def compare(
     ruff1: Path,
     ruff2: Path,
     repo: Repository,
-    checkouts: Optional[Path] = None,
+    checkouts: Path | None = None,
 ) -> Diff | None:
     """Check a specific repository against two versions of ruff."""
     removed, added = set(), set()
@@ -254,8 +255,8 @@ async def main(
     *,
     ruff1: Path,
     ruff2: Path,
-    projects_jsonl: Optional[Path],
-    checkouts: Optional[Path] = None,
+    projects_jsonl: Path | None,
+    checkouts: Path | None = None,
 ) -> None:
     """Check two versions of ruff against a corpus of open-source code."""
     if projects_jsonl: