[flake8-async] Take pathlib.Path into account when analyzing asyn…

…c functions (#9703)

## Summary

This review contains a fix for
[ASYNC101](https://docs.astral.sh/ruff/rules/open-sleep-or-subprocess-in-async-function/)
(open-sleep-or-subprocess-in-async-function)

The problem is that ruff does not take open calls from pathlib.Path into
account in async functions. Path.open() call is still a blocking call.
In addition, PTH123 suggests to use pathlib.Path instead of os.open. So
this might create an additional confusion.

See: #6892

## Test Plan

```bash
cargo test
```

crates/ruff_linter/resources/test/fixtures/flake8_async/ASYNC101.py

@@ -1,31 +1,87 @@
 import os
 import subprocess
 import time
+from pathlib import Path
 
+# Violation cases:
 
-async def foo():
+
+async def func():
     open("foo")
 
 
-async def foo():
+async def func():
     time.sleep(1)
 
 
-async def foo():
+async def func():
     subprocess.run("foo")
 
 
-async def foo():
+async def func():
     subprocess.call("foo")
 
 
-async def foo():
+async def func():
     subprocess.foo(0)
 
 
-async def foo():
+async def func():
     os.wait4(10)
 
 
-async def foo():
+async def func():
     os.wait(12)
+
+
+# Violation cases for pathlib:
+
+
+async def func():
+    Path("foo").open()  # ASYNC101
+
+
+async def func():
+    p = Path("foo")
+    p.open()  # ASYNC101
+
+
+async def func():
+    with Path("foo").open() as f:  # ASYNC101
+        pass
+
+
+async def func() -> None:
+    p = Path("foo")
+
+    async def bar():
+        p.open()  # ASYNC101
+
+
+async def func() -> None:
+    (p1, p2) = (Path("foo"), Path("bar"))
+
+    p1.open()  # ASYNC101
+
+
+# Non-violation cases for pathlib:
+
+
+class Foo:
+    def open(self):
+        pass
+
+
+async def func():
+    Foo().open()  # OK
+
+
+async def func():
+    def open():
+        pass
+
+    open()  # OK
+
+
+def func():
+    Path("foo").open()  # OK

crates/ruff_linter/src/rules/flake8_async/rules/open_sleep_or_subprocess_call.rs

@@ -1,8 +1,7 @@
-use ruff_python_ast::ExprCall;
-
 use ruff_diagnostics::{Diagnostic, Violation};
 use ruff_macros::{derive_message_formats, violation};
-use ruff_python_ast::call_path::CallPath;
+use ruff_python_ast::{self as ast, Expr};
+use ruff_python_semantic::{analyze, SemanticModel};
 use ruff_text_size::Ranged;
 
 use crate::checkers::ast::Checker;
@@ -41,37 +40,90 @@ impl Violation for OpenSleepOrSubprocessInAsyncFunction {
 }
 
 /// ASYNC101
-pub(crate) fn open_sleep_or_subprocess_call(checker: &mut Checker, call: &ExprCall) {
-    if checker.semantic().in_async_context() {
-        if checker
-            .semantic()
-            .resolve_call_path(call.func.as_ref())
-            .as_ref()
-            .is_some_and(is_open_sleep_or_subprocess_call)
-        {
-            checker.diagnostics.push(Diagnostic::new(
-                OpenSleepOrSubprocessInAsyncFunction,
-                call.func.range(),
-            ));
-        }
+pub(crate) fn open_sleep_or_subprocess_call(checker: &mut Checker, call: &ast::ExprCall) {
+    if !checker.semantic().in_async_context() {
+        return;
+    }
+
+    if is_open_sleep_or_subprocess_call(&call.func, checker.semantic())
+        || is_open_call_from_pathlib(call.func.as_ref(), checker.semantic())
+    {
+        checker.diagnostics.push(Diagnostic::new(
+            OpenSleepOrSubprocessInAsyncFunction,
+            call.func.range(),
+        ));
     }
 }
 
-fn is_open_sleep_or_subprocess_call(call_path: &CallPath) -> bool {
-    matches!(
-        call_path.as_slice(),
-        ["", "open"]
-            | ["time", "sleep"]
-            | [
-                "subprocess",
-                "run"
-                    | "Popen"
-                    | "call"
-                    | "check_call"
-                    | "check_output"
-                    | "getoutput"
-                    | "getstatusoutput"
-            ]
-            | ["os", "wait" | "wait3" | "wait4" | "waitid" | "waitpid"]
-    )
+/// Returns `true` if the expression resolves to a blocking call, like `time.sleep` or
+/// `subprocess.run`.
+fn is_open_sleep_or_subprocess_call(func: &Expr, semantic: &SemanticModel) -> bool {
+    semantic.resolve_call_path(func).is_some_and(|call_path| {
+        matches!(
+            call_path.as_slice(),
+            ["", "open"]
+                | ["time", "sleep"]
+                | [
+                    "subprocess",
+                    "run"
+                        | "Popen"
+                        | "call"
+                        | "check_call"
+                        | "check_output"
+                        | "getoutput"
+                        | "getstatusoutput"
+                ]
+                | ["os", "wait" | "wait3" | "wait4" | "waitid" | "waitpid"]
+        )
+    })
+}
+
+/// Returns `true` if an expression resolves to a call to `pathlib.Path.open`.
+fn is_open_call_from_pathlib(func: &Expr, semantic: &SemanticModel) -> bool {
+    let Expr::Attribute(ast::ExprAttribute { attr, value, .. }) = func else {
+        return false;
+    };
+
+    if attr.as_str() != "open" {
+        return false;
+    }
+
+    // First: is this an inlined call to `pathlib.Path.open`?
+    // ```python
+    // from pathlib import Path
+    // Path("foo").open()
+    // ```
+    if let Expr::Call(call) = value.as_ref() {
+        let Some(call_path) = semantic.resolve_call_path(call.func.as_ref()) else {
+            return false;
+        };
+        if call_path.as_slice() == ["pathlib", "Path"] {
+            return true;
+        }
+    }
+
+    // Second, is this a call to `pathlib.Path.open` via a variable?
+    // ```python
+    // from pathlib import Path
+    // path = Path("foo")
+    // path.open()
+    // ```
+    let Expr::Name(name) = value.as_ref() else {
+        return false;
+    };
+
+    let Some(binding_id) = semantic.resolve_name(name) else {
+        return false;
+    };
+
+    let binding = semantic.binding(binding_id);
+
+    let Some(Expr::Call(call)) = analyze::typing::find_binding_value(&name.id, binding, semantic)
+    else {
+        return false;
+    };
+
+    semantic
+        .resolve_call_path(call.func.as_ref())
+        .is_some_and(|call_path| call_path.as_slice() == ["pathlib", "Path"])
 }

crates/ruff_linter/src/rules/flake8_async/snapshots/ruff_linter__rules__flake8_async__tests__ASYNC101_ASYNC101.py.snap

@@ -1,45 +1,83 @@
 ---
 source: crates/ruff_linter/src/rules/flake8_async/mod.rs
 ---
-ASYNC101.py:7:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
-  |
-6 | async def foo():
-7 |     open("foo")
-  |     ^^^^ ASYNC101
-  |
+ASYNC101.py:10:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+   |
+ 9 | async def func():
+10 |     open("foo")
+   |     ^^^^ ASYNC101
+   |
 
-ASYNC101.py:11:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+ASYNC101.py:14:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
    |
-10 | async def foo():
-11 |     time.sleep(1)
+13 | async def func():
+14 |     time.sleep(1)
    |     ^^^^^^^^^^ ASYNC101
    |
 
-ASYNC101.py:15:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+ASYNC101.py:18:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
    |
-14 | async def foo():
-15 |     subprocess.run("foo")
+17 | async def func():
+18 |     subprocess.run("foo")
    |     ^^^^^^^^^^^^^^ ASYNC101
    |
 
-ASYNC101.py:19:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+ASYNC101.py:22:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
    |
-18 | async def foo():
-19 |     subprocess.call("foo")
+21 | async def func():
+22 |     subprocess.call("foo")
    |     ^^^^^^^^^^^^^^^ ASYNC101
    |
 
-ASYNC101.py:27:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+ASYNC101.py:30:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
    |
-26 | async def foo():
-27 |     os.wait4(10)
+29 | async def func():
+30 |     os.wait4(10)
    |     ^^^^^^^^ ASYNC101
    |
 
-ASYNC101.py:31:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+ASYNC101.py:34:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+   |
+33 | async def func():
+34 |     os.wait(12)
+   |     ^^^^^^^ ASYNC101
+   |
+
+ASYNC101.py:41:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+   |
+40 | async def func():
+41 |     Path("foo").open()  # ASYNC101
+   |     ^^^^^^^^^^^^^^^^ ASYNC101
+   |
+
+ASYNC101.py:46:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+   |
+44 | async def func():
+45 |     p = Path("foo")
+46 |     p.open()  # ASYNC101
+   |     ^^^^^^ ASYNC101
+   |
+
+ASYNC101.py:50:10: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+   |
+49 | async def func():
+50 |     with Path("foo").open() as f:  # ASYNC101
+   |          ^^^^^^^^^^^^^^^^ ASYNC101
+51 |         pass
+   |
+
+ASYNC101.py:58:9: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
+   |
+57 |     async def bar():
+58 |         p.open()  # ASYNC101
+   |         ^^^^^^ ASYNC101
+   |
+
+ASYNC101.py:64:5: ASYNC101 Async functions should not call `open`, `time.sleep`, or `subprocess` methods
    |
-30 | async def foo():
-31 |     os.wait(12)
+62 |     (p1, p2) = (Path("foo"), Path("bar"))
+63 | 
+64 |     p1.open()  # ASYNC101
    |     ^^^^^^^ ASYNC101
    |