fix(migrate): emit a single --check when rewriting prettier scripts

Author: shulaoda

crates/vite_migration/src/prettier.rs

@@ -225,6 +225,15 @@ mod tests {
             rewrite_prettier_script("prettier --check --list-different ."),
             "vp fmt --check ."
         );
+
+        // --list-different + --check (the other order) → still a single --check
+        assert_eq!(
+            rewrite_prettier_script("prettier --list-different --check ."),
+            "vp fmt --check ."
+        );
+
+        // two literal --check → still a single --check
+        assert_eq!(rewrite_prettier_script("prettier --check --check ."), "vp fmt --check .");
     }
 
     #[test]

crates/vite_migration/src/script_rewrite.rs

@@ -497,7 +497,14 @@ fn strip_flags_from_suffix(
                     break;
                 }
                 if val == conv.dedup_flag {
-                    conversion_emitted[ci] = true;
+                    // Drop a duplicate if the target flag was already emitted;
+                    // otherwise keep this one and mark it emitted.
+                    if conversion_emitted[ci] {
+                        converted = true;
+                    } else {
+                        conversion_emitted[ci] = true;
+                    }
+                    break;
                 }
             }
             if converted {