Support 'reason' argument to pytest.fail (#5040)

## Summary

Per the [API
reference](https://docs.pytest.org/en/7.1.x/reference/reference.html#pytest.fail),
`reason` was added in version 7, and is equivalent to `msg` (but
preferred going forward).

I also grepped for `msg` usages in `flake8_pytest_style`, but found no
others (apart from those that reference `unittest` APIs.)

Closes #3387.

crates/ruff/resources/test/fixtures/flake8_pytest_style/PT016.py

@@ -1,17 +1,25 @@
 import pytest
 
 
-def test_xxx():
+# OK
-    pytest.fail("this is a failure")  # Test OK arg
+def f():
+    pytest.fail("this is a failure")
 
 
-def test_xxx():
+def f():
-    pytest.fail(msg="this is a failure")  # Test OK kwarg
+    pytest.fail(msg="this is a failure")
 
 
-def test_xxx():  # Error
+def f():
+    pytest.fail(reason="this is a failure")
+
+
+# Errors
+def f():
     pytest.fail()
     pytest.fail("")
     pytest.fail(f"")
     pytest.fail(msg="")
     pytest.fail(msg=f"")
+    pytest.fail(reason="")
+    pytest.fail(reason=f"")

crates/ruff/src/rules/flake8_pytest_style/rules/fail.rs

@@ -21,7 +21,12 @@ impl Violation for PytestFailWithoutMessage {
 pub(crate) fn fail_call(checker: &mut Checker, func: &Expr, args: &[Expr], keywords: &[Keyword]) {
     if is_pytest_fail(checker.semantic_model(), func) {
         let call_args = SimpleCallArgs::new(args, keywords);
-        let msg = call_args.argument("msg", 0);
+
+        // Allow either `pytest.fail(reason="...")` (introduced in pytest 7.0) or
+        // `pytest.fail(msg="...")` (deprecated in pytest 7.0)
+        let msg = call_args
+            .argument("reason", 0)
+            .or_else(|| call_args.argument("msg", 0));
 
         if let Some(msg) = msg {
             if is_empty_or_null_string(msg) {

crates/ruff/src/rules/flake8_pytest_style/rules/unittest_assert.rs

@@ -206,9 +206,7 @@ impl UnittestAssert {
         keywords: &'a [Keyword],
     ) -> Result<FxHashMap<&'a str, &'a Expr>> {
         // If we have variable-length arguments, abort.
-        if args.iter().any(|arg| matches!(arg, Expr::Starred(_)))
+        if args.iter().any(Expr::is_starred_expr) || keywords.iter().any(|kw| kw.arg.is_none()) {
-            || keywords.iter().any(|kw| kw.arg.is_none())
-        {
             bail!("Variable-length arguments are not supported");
         }
 
@@ -263,14 +261,14 @@ impl UnittestAssert {
                     .ok_or_else(|| anyhow!("Missing argument `expr`"))?;
                 let msg = args.get("msg").copied();
                 Ok(if matches!(self, UnittestAssert::False) {
-                    let node = expr.clone();
+                    assert(
-                    let node1 = Expr::UnaryOp(ast::ExprUnaryOp {
+                        &Expr::UnaryOp(ast::ExprUnaryOp {
-                        op: Unaryop::Not,
+                            op: Unaryop::Not,
-                        operand: Box::new(node),
+                            operand: Box::new(expr.clone()),
-                        range: TextRange::default(),
+                            range: TextRange::default(),
-                    });
+                        }),
-                    let unary_expr = node1;
+                        msg,
-                    assert(&unary_expr, msg)
+                    )
                 } else {
                     assert(expr, msg)
                 })

crates/ruff/src/rules/flake8_pytest_style/snapshots/ruff__rules__flake8_pytest_style__tests__PT016.snap

@@ -1,49 +1,70 @@
 ---
 source: crates/ruff/src/rules/flake8_pytest_style/mod.rs
 ---
-PT016.py:13:5: PT016 No message passed to `pytest.fail()`
+PT016.py:19:5: PT016 No message passed to `pytest.fail()`
    |
-12 | def test_xxx():  # Error
+17 | # Errors
-13 |     pytest.fail()
+18 | def f():
+19 |     pytest.fail()
    |     ^^^^^^^^^^^ PT016
-14 |     pytest.fail("")
+20 |     pytest.fail("")
-15 |     pytest.fail(f"")
+21 |     pytest.fail(f"")
    |
 
-PT016.py:14:5: PT016 No message passed to `pytest.fail()`
+PT016.py:20:5: PT016 No message passed to `pytest.fail()`
    |
-12 | def test_xxx():  # Error
+18 | def f():
-13 |     pytest.fail()
+19 |     pytest.fail()
-14 |     pytest.fail("")
+20 |     pytest.fail("")
    |     ^^^^^^^^^^^ PT016
-15 |     pytest.fail(f"")
+21 |     pytest.fail(f"")
-16 |     pytest.fail(msg="")
+22 |     pytest.fail(msg="")
    |
 
-PT016.py:15:5: PT016 No message passed to `pytest.fail()`
+PT016.py:21:5: PT016 No message passed to `pytest.fail()`
    |
-13 |     pytest.fail()
+19 |     pytest.fail()
-14 |     pytest.fail("")
+20 |     pytest.fail("")
-15 |     pytest.fail(f"")
+21 |     pytest.fail(f"")
    |     ^^^^^^^^^^^ PT016
-16 |     pytest.fail(msg="")
+22 |     pytest.fail(msg="")
-17 |     pytest.fail(msg=f"")
+23 |     pytest.fail(msg=f"")
    |
 
-PT016.py:16:5: PT016 No message passed to `pytest.fail()`
+PT016.py:22:5: PT016 No message passed to `pytest.fail()`
    |
-14 |     pytest.fail("")
+20 |     pytest.fail("")
-15 |     pytest.fail(f"")
+21 |     pytest.fail(f"")
-16 |     pytest.fail(msg="")
+22 |     pytest.fail(msg="")
    |     ^^^^^^^^^^^ PT016
-17 |     pytest.fail(msg=f"")
+23 |     pytest.fail(msg=f"")
+24 |     pytest.fail(reason="")
    |
 
-PT016.py:17:5: PT016 No message passed to `pytest.fail()`
+PT016.py:23:5: PT016 No message passed to `pytest.fail()`
    |
-15 |     pytest.fail(f"")
+21 |     pytest.fail(f"")
-16 |     pytest.fail(msg="")
+22 |     pytest.fail(msg="")
-17 |     pytest.fail(msg=f"")
+23 |     pytest.fail(msg=f"")
+   |     ^^^^^^^^^^^ PT016
+24 |     pytest.fail(reason="")
+25 |     pytest.fail(reason=f"")
+   |
+
+PT016.py:24:5: PT016 No message passed to `pytest.fail()`
+   |
+22 |     pytest.fail(msg="")
+23 |     pytest.fail(msg=f"")
+24 |     pytest.fail(reason="")
+   |     ^^^^^^^^^^^ PT016
+25 |     pytest.fail(reason=f"")
+   |
+
+PT016.py:25:5: PT016 No message passed to `pytest.fail()`
+   |
+23 |     pytest.fail(msg=f"")
+24 |     pytest.fail(reason="")
+25 |     pytest.fail(reason=f"")
    |     ^^^^^^^^^^^ PT016
    |