gate syntax error reporting behind preview

Author: ntBre

crates/ruff/tests/lint.rs

@@ -2653,7 +2653,7 @@ match 2:
     "
     );
 
-    // syntax error on 3.9
+    // ok on 3.9 without preview
     assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
         .args(STDIN_BASE_OPTIONS)
         .args(["--stdin-filename", "test.py"])
@@ -2664,6 +2664,30 @@ match 2:
 match 2:
     case 1:
         print("it's one")
+"#
+        ),
+        @r"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+    All checks passed!
+
+    ----- stderr -----
+    "
+    );
+
+    // syntax error on 3.9 with preview
+    assert_cmd_snapshot!(Command::new(get_cargo_bin(BIN_NAME))
+        .args(STDIN_BASE_OPTIONS)
+        .args(["--stdin-filename", "test.py"])
+        .arg("--target-version=py39")
+        .arg("--preview")
+        .arg("-")
+        .pass_stdin(
+            r#"
+match 2:
+    case 1:
+        print("it's one")
 "#
         ),
         @r"

crates/ruff_linter/src/linter.rs

@@ -429,11 +429,17 @@ pub fn lint_only(
         &parsed,
     );
 
+    let syntax_errors = if settings.preview.is_enabled() {
+        parsed.syntax_errors()
+    } else {
+        &[]
+    };
+
     LinterResult {
         messages: diagnostics_to_messages(
             diagnostics,
             parsed.errors(),
-            parsed.syntax_errors(),
+            syntax_errors,
             path,
             &locator,
             &directives,
@@ -582,12 +588,18 @@ pub fn lint_fix<'a>(
             report_failed_to_converge_error(path, transformed.source_code(), &diagnostics);
         }
 
+        let syntax_errors = if settings.preview.is_enabled() {
+            parsed.syntax_errors()
+        } else {
+            &[]
+        };
+
         return Ok(FixerResult {
             result: LinterResult {
                 messages: diagnostics_to_messages(
                     diagnostics,
                     parsed.errors(),
-                    parsed.syntax_errors(),
+                    syntax_errors,
                     path,
                     &locator,
                     &directives,