Avoid panic in QueryBuilder::reset

Author: joeydewaal

sqlx-core/src/query_builder.rs

@@ -517,7 +517,9 @@ where
     /// The query is truncated to the initial fragment provided to [`new()`][Self::new] and
     /// the bind arguments are reset.
     pub fn reset(&mut self) -> &mut Self {
-        let query: &mut String = Arc::get_mut(&mut self.query).expect(ERROR);
+        // Someone can hold onto a clone of `self.query` by calling build and not executing the
+        // query. To avoid panicking here we might as well allocate a new `String`.
+        let query: &mut String = Arc::make_mut(&mut self.query);
         query.truncate(self.init_len);
         self.arguments = Some(Default::default());
 

tests/postgres/query_builder.rs

@@ -79,12 +79,10 @@ fn test_reset() {
 fn test_query_builder_reuse() {
     let mut qb: QueryBuilder<'_, Postgres> = QueryBuilder::new("");
 
-    {
-        let _query = qb
-            .push("SELECT * FROM users WHERE id = ")
-            .push_bind(42i32)
-            .build();
-    }
+    let _query = qb
+        .push("SELECT * FROM users WHERE id = ")
+        .push_bind(42i32)
+        .build();
 
     qb.reset();