Disable auto-fix when source has syntax errors (#12134)

## Summary

This PR updates Ruff to **not** generate auto-fixes if the source code
contains syntax errors as determined by the parser.

The main motivation behind this is to avoid infinite autofix loop when
the token-based rules are run over any source with syntax errors in
#11950.

Although even after this, it's not certain that there won't be an
infinite autofix loop because the logic might be incorrect. For example,
#12094 and
#12136.

This requires updating the test infrastructure to not validate for fix
availability status when the source contained syntax errors. This is
required because otherwise the fuzzer might fail as it uses the test
function to run the linter and validate the source code.

resolves: #11455 

## Test Plan

`cargo insta test`

crates/ruff_linter/resources/test/fixtures/flake8_commas/COM81.py

@@ -565,10 +565,6 @@ def foo(
     **kwargs
 }
 
-(
-    *args
-)
-
 {
     *args
 }

crates/ruff_linter/resources/test/fixtures/flake8_commas/COM81_syntax_error.py

@@ -0,0 +1,3 @@
+(
+    *args
+)

crates/ruff_linter/src/linter.rs

@@ -288,23 +288,30 @@ pub fn check_path(
         }
     }
 
-    // Remove fixes for any rules marked as unfixable.
-    for diagnostic in &mut diagnostics {
-        if !settings.rules.should_fix(diagnostic.kind.rule()) {
-            diagnostic.fix = None;
+    if parsed.is_valid() {
+        // Remove fixes for any rules marked as unfixable.
+        for diagnostic in &mut diagnostics {
+            if !settings.rules.should_fix(diagnostic.kind.rule()) {
+                diagnostic.fix = None;
+            }
         }
-    }
 
-    // Update fix applicability to account for overrides
-    if !settings.fix_safety.is_empty() {
-        for diagnostic in &mut diagnostics {
-            if let Some(fix) = diagnostic.fix.take() {
-                let fixed_applicability = settings
-                    .fix_safety
-                    .resolve_applicability(diagnostic.kind.rule(), fix.applicability());
-                diagnostic.set_fix(fix.with_applicability(fixed_applicability));
+        // Update fix applicability to account for overrides
+        if !settings.fix_safety.is_empty() {
+            for diagnostic in &mut diagnostics {
+                if let Some(fix) = diagnostic.fix.take() {
+                    let fixed_applicability = settings
+                        .fix_safety
+                        .resolve_applicability(diagnostic.kind.rule(), fix.applicability());
+                    diagnostic.set_fix(fix.with_applicability(fixed_applicability));
+                }
             }
         }
+    } else {
+        // Avoid fixing in case the source code contains syntax errors.
+        for diagnostic in &mut diagnostics {
+            diagnostic.fix = None;
+        }
     }
 
     diagnostics

crates/ruff_linter/src/rules/flake8_commas/mod.rs

@@ -13,6 +13,7 @@ mod tests {
     use crate::{assert_messages, settings};
 
     #[test_case(Path::new("COM81.py"))]
+    #[test_case(Path::new("COM81_syntax_error.py"))]
     fn rules(path: &Path) -> Result<()> {
         let snapshot = path.to_string_lossy().into_owned();
         let diagnostics = test_path(

crates/ruff_linter/src/rules/flake8_commas/snapshots/ruff_linter__rules__flake8_commas__tests__COM81.py.snap

@@ -796,192 +796,184 @@ COM81.py:565:13: COM812 [*] Trailing comma missing
     565 |+    **kwargs,
 566 566 | }
 567 567 | 
-568 568 | (
+568 568 | {
 
-COM81.py:569:5: SyntaxError: Starred expression cannot be used here
+COM81.py:569:10: COM812 [*] Trailing comma missing
     |
-568 | (
+568 | {
 569 |     *args
-    |     ^
-570 | )
+    |           COM812
+570 | }
     |
+    = help: Add trailing comma
+
+ℹ Safe fix
+566 566 | }
+567 567 | 
+568 568 | {
+569     |-    *args
+    569 |+    *args,
+570 570 | }
+571 571 | 
+572 572 | [
 
 COM81.py:573:10: COM812 [*] Trailing comma missing
     |
-572 | {
+572 | [
 573 |     *args
     |           COM812
-574 | }
+574 | ]
     |
     = help: Add trailing comma
 
 ℹ Safe fix
-570 570 | )
+570 570 | }
 571 571 | 
-572 572 | {
+572 572 | [
 573     |-    *args
     573 |+    *args,
-574 574 | }
+574 574 | ]
 575 575 | 
-576 576 | [
+576 576 | def foo(
 
-COM81.py:577:10: COM812 [*] Trailing comma missing
+COM81.py:579:10: COM812 [*] Trailing comma missing
     |
-576 | [
-577 |     *args
+577 |     ham,
+578 |     spam,
+579 |     *args
     |           COM812
-578 | ]
+580 |     ):
+581 |     pass
     |
     = help: Add trailing comma
 
 ℹ Safe fix
-574 574 | }
-575 575 | 
-576 576 | [
-577     |-    *args
-    577 |+    *args,
-578 578 | ]
-579 579 | 
-580 580 | def foo(
-
-COM81.py:583:10: COM812 [*] Trailing comma missing
-    |
-581 |     ham,
-582 |     spam,
-583 |     *args
-    |           COM812
-584 |     ):
-585 |     pass
-    |
-    = help: Add trailing comma
+576 576 | def foo(
+577 577 |     ham,
+578 578 |     spam,
+579     |-    *args
+    579 |+    *args,
+580 580 |     ):
+581 581 |     pass
+582 582 | 
 
-ℹ Safe fix
-580 580 | def foo(
-581 581 |     ham,
-582 582 |     spam,
-583     |-    *args
-    583 |+    *args,
-584 584 |     ):
-585 585 |     pass
-586 586 | 
-
-COM81.py:590:13: COM812 [*] Trailing comma missing
+COM81.py:586:13: COM812 [*] Trailing comma missing
     |
-588 |     ham,
-589 |     spam,
-590 |     **kwargs
+584 |     ham,
+585 |     spam,
+586 |     **kwargs
     |              COM812
-591 |     ):
-592 |     pass
+587 |     ):
+588 |     pass
     |
     = help: Add trailing comma
 
 ℹ Safe fix
-587 587 | def foo(
-588 588 |     ham,
-589 589 |     spam,
-590     |-    **kwargs
-    590 |+    **kwargs,
-591 591 |     ):
-592 592 |     pass
-593 593 | 
+583 583 | def foo(
+584 584 |     ham,
+585 585 |     spam,
+586     |-    **kwargs
+    586 |+    **kwargs,
+587 587 |     ):
+588 588 |     pass
+589 589 | 
 
-COM81.py:598:15: COM812 [*] Trailing comma missing
+COM81.py:594:15: COM812 [*] Trailing comma missing
     |
-596 |     spam,
-597 |     *args,
-598 |     kwarg_only
+592 |     spam,
+593 |     *args,
+594 |     kwarg_only
     |                COM812
-599 |     ):
-600 |     pass
+595 |     ):
+596 |     pass
     |
     = help: Add trailing comma
 
 ℹ Safe fix
-595 595 |     ham,
-596 596 |     spam,
-597 597 |     *args,
-598     |-    kwarg_only
-    598 |+    kwarg_only,
-599 599 |     ):
-600 600 |     pass
-601 601 | 
+591 591 |     ham,
+592 592 |     spam,
+593 593 |     *args,
+594     |-    kwarg_only
+    594 |+    kwarg_only,
+595 595 |     ):
+596 596 |     pass
+597 597 | 
 
-COM81.py:627:20: COM812 [*] Trailing comma missing
+COM81.py:623:20: COM812 [*] Trailing comma missing
     |
-625 |     foo,
-626 |     bar,
-627 |     **{'ham': spam}
+621 |     foo,
+622 |     bar,
+623 |     **{'ham': spam}
     |                     COM812
-628 | )
+624 | )
     |
     = help: Add trailing comma
 
 ℹ Safe fix
-624 624 | result = function(
-625 625 |     foo,
-626 626 |     bar,
-627     |-    **{'ham': spam}
-    627 |+    **{'ham': spam},
-628 628 | )
-629 629 | 
-630 630 | # Make sure the COM812 and UP034 rules don't fix simultaneously and cause a syntax error.
+620 620 | result = function(
+621 621 |     foo,
+622 622 |     bar,
+623     |-    **{'ham': spam}
+    623 |+    **{'ham': spam},
+624 624 | )
+625 625 | 
+626 626 | # Make sure the COM812 and UP034 rules don't fix simultaneously and cause a syntax error.
 
-COM81.py:632:42: COM812 [*] Trailing comma missing
+COM81.py:628:42: COM812 [*] Trailing comma missing
     |
-630 | # Make sure the COM812 and UP034 rules don't fix simultaneously and cause a syntax error.
-631 | the_first_one = next(
-632 |     (i for i in range(10) if i // 2 == 0)  # COM812 fix should include the final bracket
+626 | # Make sure the COM812 and UP034 rules don't fix simultaneously and cause a syntax error.
+627 | the_first_one = next(
+628 |     (i for i in range(10) if i // 2 == 0)  # COM812 fix should include the final bracket
     |                                           COM812
-633 | )
+629 | )
     |
     = help: Add trailing comma
 
 ℹ Safe fix
-629 629 | 
-630 630 | # Make sure the COM812 and UP034 rules don't fix simultaneously and cause a syntax error.
-631 631 | the_first_one = next(
-632     |-    (i for i in range(10) if i // 2 == 0)  # COM812 fix should include the final bracket
-    632 |+    (i for i in range(10) if i // 2 == 0),  # COM812 fix should include the final bracket
-633 633 | )
-634 634 | 
-635 635 | foo = namedtuple(
+625 625 | 
+626 626 | # Make sure the COM812 and UP034 rules don't fix simultaneously and cause a syntax error.
+627 627 | the_first_one = next(
+628     |-    (i for i in range(10) if i // 2 == 0)  # COM812 fix should include the final bracket
+    628 |+    (i for i in range(10) if i // 2 == 0),  # COM812 fix should include the final bracket
+629 629 | )
+630 630 | 
+631 631 | foo = namedtuple(
 
-COM81.py:644:46: COM819 [*] Trailing comma prohibited
+COM81.py:640:46: COM819 [*] Trailing comma prohibited
     |
-643 | # F-strings
-644 | kwargs.pop("remove", f"this {trailing_comma}",)
+639 | # F-strings
+640 | kwargs.pop("remove", f"this {trailing_comma}",)
     |                                              ^ COM819
-645 | 
-646 | raise Exception(
+641 | 
+642 | raise Exception(
     |
     = help: Remove trailing comma
 
 ℹ Safe fix
-641 641 | )
-642 642 | 
-643 643 | # F-strings
-644     |-kwargs.pop("remove", f"this {trailing_comma}",)
-    644 |+kwargs.pop("remove", f"this {trailing_comma}")
-645 645 | 
-646 646 | raise Exception(
-647 647 |     "first", extra=f"Add trailing comma here ->"
+637 637 | )
+638 638 | 
+639 639 | # F-strings
+640     |-kwargs.pop("remove", f"this {trailing_comma}",)
+    640 |+kwargs.pop("remove", f"this {trailing_comma}")
+641 641 | 
+642 642 | raise Exception(
+643 643 |     "first", extra=f"Add trailing comma here ->"
 
-COM81.py:647:49: COM812 [*] Trailing comma missing
+COM81.py:643:49: COM812 [*] Trailing comma missing
     |
-646 | raise Exception(
-647 |     "first", extra=f"Add trailing comma here ->"
+642 | raise Exception(
+643 |     "first", extra=f"Add trailing comma here ->"
     |                                                  COM812
-648 | )
+644 | )
     |
     = help: Add trailing comma
 
 ℹ Safe fix
-644 644 | kwargs.pop("remove", f"this {trailing_comma}",)
+640 640 | kwargs.pop("remove", f"this {trailing_comma}",)
+641 641 | 
+642 642 | raise Exception(
+643     |-    "first", extra=f"Add trailing comma here ->"
+    643 |+    "first", extra=f"Add trailing comma here ->",
+644 644 | )
 645 645 | 
-646 646 | raise Exception(
-647     |-    "first", extra=f"Add trailing comma here ->"
-    647 |+    "first", extra=f"Add trailing comma here ->",
-648 648 | )
-649 649 | 
-650 650 | assert False, f"<- This is not a trailing comma"
+646 646 | assert False, f"<- This is not a trailing comma"

crates/ruff_linter/src/rules/flake8_commas/snapshots/ruff_linter__rules__flake8_commas__tests__COM81_syntax_error.py.snap

@@ -0,0 +1,10 @@
+---
+source: crates/ruff_linter/src/rules/flake8_commas/mod.rs
+---
+COM81_syntax_error.py:2:5: SyntaxError: Starred expression cannot be used here
+  |
+1 | (
+2 |     *args
+  |     ^
+3 | )
+  |