[flake8-pie] Omit bound tuples passed to .startswith or `.endswit…

…h` (#9661)

## Summary

This review contains a fix for
[PIE810](https://docs.astral.sh/ruff/rules/multiple-starts-ends-with/)
(multiple-starts-ends-with)

The problem is that ruff suggests combining multiple startswith/endswith
calls into a single call even though there might be a call with tuple of
strs. This leads to calling startswith/endswith with tuple of tuple of
strs which is incorrect and violates startswith/endswith conctract and
results in runtime failure.

However the following will be valid and fixed correctly => 
```python
x = ("hello", "world")
y = "h"
z = "w"
msg = "hello world"

if msg.startswith(x) or msg.startswith(y) or msg.startswith(z) :
      sys.exit(1)
```
```
ruff --fix --select PIE810 --unsafe-fixes
```
=> 
```python
if msg.startswith(x) or msg.startswith((y,z)):
      sys.exit(1)
```

See: #8906

## Test Plan

```bash
cargo test
```

crates/ruff_linter/resources/test/fixtures/flake8_pie/PIE810.py

@@ -9,6 +9,22 @@
 # error
 obj.endswith(foo) or obj.startswith(foo) or obj.startswith("foo")
 
+def func():
+    msg = "hello world"
+
+    x = "h"
+    y = ("h", "e", "l", "l", "o")  
+    z = "w"
+
+    if msg.startswith(x) or msg.startswith(y) or msg.startswith(z): # Error
+        print("yes") 
+
+def func():
+    msg = "hello world"
+
+    if msg.startswith(("h", "e", "l", "l", "o")) or msg.startswith("h") or msg.startswith("w"): # Error
+        print("yes") 
+
 # ok
 obj.startswith(("foo",  "bar"))
 # ok
@@ -17,3 +33,46 @@
 obj.startswith("foo") or obj.endswith("bar")
 # ok
 obj.startswith("foo") or abc.startswith("bar")
+
+def func():
+    msg = "hello world"
+
+    x = "h"
+    y = ("h", "e", "l", "l", "o")  
+
+    if msg.startswith(x) or msg.startswith(y): # OK
+        print("yes") 
+
+def func():
+    msg = "hello world"
+
+    y = ("h", "e", "l", "l", "o")  
+
+    if msg.startswith(y): # OK
+        print("yes") 
+
+def func():
+    msg = "hello world"
+
+    y = ("h", "e", "l", "l", "o")  
+
+    if msg.startswith(y) or msg.startswith(y): # OK
+        print("yes") 
+
+def func():
+    msg = "hello world"
+
+    y = ("h", "e", "l", "l", "o")  
+    x = ("w", "o", "r", "l", "d")
+
+    if msg.startswith(y) or msg.startswith(x) or msg.startswith("h"): # OK
+        print("yes") 
+
+def func():
+    msg = "hello world"
+
+    y = ("h", "e", "l", "l", "o")  
+    x = ("w", "o", "r", "l", "d")
+
+    if msg.startswith(y) or msg.endswith(x) or msg.startswith("h"): # OK
+        print("yes")

crates/ruff_linter/src/rules/flake8_pie/rules/multiple_starts_ends_with.rs

@@ -3,6 +3,7 @@ use std::iter;
 
 use itertools::Either::{Left, Right};
 
+use ruff_python_semantic::{analyze, SemanticModel};
 use ruff_text_size::{Ranged, TextRange};
 
 use ruff_python_ast::{self as ast, Arguments, BoolOp, Expr, ExprContext, Identifier};
@@ -36,6 +37,14 @@ use crate::checkers::ast::Checker;
 ///     print("Greetings!")
 /// ```
 ///
+/// ## Fix safety
+/// This rule's fix is unsafe, as in some cases, it will be unable to determine
+/// whether the argument to an existing `.startswith` or `.endswith` call is a
+/// tuple. For example, given `msg.startswith(x) or msg.startswith(y)`, if `x`
+/// or `y` is a tuple, and the semantic model is unable to detect it as such,
+/// the rule will suggest `msg.startswith((x, y))`, which will error at
+/// runtime.
+///
 /// ## References
 /// - [Python documentation: `str.startswith`](https://docs.python.org/3/library/stdtypes.html#str.startswith)
 /// - [Python documentation: `str.endswith`](https://docs.python.org/3/library/stdtypes.html#str.endswith)
@@ -84,10 +93,14 @@ pub(crate) fn multiple_starts_ends_with(checker: &mut Checker, expr: &Expr) {
             continue;
         };
 
-        if !(args.len() == 1 && keywords.is_empty()) {
+        if !keywords.is_empty() {
             continue;
         }
 
+        let [arg] = args.as_slice() else {
+            continue;
+        };
+
         let Expr::Attribute(ast::ExprAttribute { value, attr, .. }) = func.as_ref() else {
             continue;
         };
@@ -99,6 +112,13 @@ pub(crate) fn multiple_starts_ends_with(checker: &mut Checker, expr: &Expr) {
             continue;
         };
 
+        // If the argument is bound to a tuple, skip it, since we don't want to suggest
+        // `startswith((x, y))` where `x` or `y` are tuples. (Tuple literals are okay, since we
+        // inline them below.)
+        if is_bound_to_tuple(arg, checker.semantic()) {
+            continue;
+        }
+
         duplicates
             .entry((attr.as_str(), arg_name.as_str()))
             .or_insert_with(Vec::new)
@@ -149,7 +169,7 @@ pub(crate) fn multiple_starts_ends_with(checker: &mut Checker, expr: &Expr) {
                             Right(iter::once(*value))
                         }
                     })
-                    .map(Clone::clone)
+                    .cloned()
                     .collect(),
                 ctx: ExprContext::Load,
                 range: TextRange::default(),
@@ -202,3 +222,18 @@ pub(crate) fn multiple_starts_ends_with(checker: &mut Checker, expr: &Expr) {
         }
     }
 }
+
+/// Returns `true` if the expression definitively resolves to a tuple (e.g., `x` in `x = (1, 2)`).
+fn is_bound_to_tuple(arg: &Expr, semantic: &SemanticModel) -> bool {
+    let Expr::Name(ast::ExprName { id, .. }) = arg else {
+        return false;
+    };
+
+    let Some(binding_id) = semantic.lookup_symbol(id.as_str()) else {
+        return false;
+    };
+
+    let binding = semantic.binding(binding_id);
+
+    analyze::typing::is_tuple(binding, semantic)
+}

crates/ruff_linter/src/rules/flake8_pie/snapshots/ruff_linter__rules__flake8_pie__tests__PIE810_PIE810.py.snap

@@ -89,7 +89,7 @@ PIE810.py:10:1: PIE810 [*] Call `startswith` once with a `tuple`
 10 | obj.endswith(foo) or obj.startswith(foo) or obj.startswith("foo")
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PIE810
 11 | 
-12 | # ok
+12 | def func():
    |
    = help: Merge into a single `startswith` call
 
@@ -100,7 +100,47 @@ PIE810.py:10:1: PIE810 [*] Call `startswith` once with a `tuple`
 10    |-obj.endswith(foo) or obj.startswith(foo) or obj.startswith("foo")
    10 |+obj.endswith(foo) or obj.startswith((foo, "foo"))
 11 11 | 
-12 12 | # ok
-13 13 | obj.startswith(("foo",  "bar"))
+12 12 | def func():
+13 13 |     msg = "hello world"
+
+PIE810.py:19:8: PIE810 [*] Call `startswith` once with a `tuple`
+   |
+17 |     z = "w"
+18 | 
+19 |     if msg.startswith(x) or msg.startswith(y) or msg.startswith(z): # Error
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PIE810
+20 |         print("yes") 
+   |
+   = help: Merge into a single `startswith` call
+
+ℹ Unsafe fix
+16 16 |     y = ("h", "e", "l", "l", "o")  
+17 17 |     z = "w"
+18 18 | 
+19    |-    if msg.startswith(x) or msg.startswith(y) or msg.startswith(z): # Error
+   19 |+    if msg.startswith((x, z)) or msg.startswith(y): # Error
+20 20 |         print("yes") 
+21 21 | 
+22 22 | def func():
+
+PIE810.py:25:8: PIE810 [*] Call `startswith` once with a `tuple`
+   |
+23 |     msg = "hello world"
+24 | 
+25 |     if msg.startswith(("h", "e", "l", "l", "o")) or msg.startswith("h") or msg.startswith("w"): # Error
+   |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PIE810
+26 |         print("yes") 
+   |
+   = help: Merge into a single `startswith` call
+
+ℹ Unsafe fix
+22 22 | def func():
+23 23 |     msg = "hello world"
+24 24 | 
+25    |-    if msg.startswith(("h", "e", "l", "l", "o")) or msg.startswith("h") or msg.startswith("w"): # Error
+   25 |+    if msg.startswith(("h", "e", "l", "l", "o", "h", "w")): # Error
+26 26 |         print("yes") 
+27 27 | 
+28 28 | # ok