SQLX unwraps internally when there are comments in the query

[PonasKovas]

Hello, my program panics because sqlx unwraps on sqlx-core/src/sqlite/statement.rs:97:43. No error messages or anything.

I'll try to isolate the code that causes this right now, any idea what this could be?

[PonasKovas]

Isolated:

use sqlx::{Connect, Executor};
use sqlx::sqlite::SqliteConnection;

#[tokio::main]
async fn main() {
    let mut conn = SqliteConnection::connect("sqlite://test.db").await.unwrap();
    
    conn.execute("-- comment").await.unwrap();
}

Apparently I can't have comments in my queries.

[PonasKovas]

And this is not because there is no actual query (just a comment), as the same error happens when there are comments alongside normal queries.

[mehcode]

Interesting edge case. I would expect this to just work.

[izik1]

Hi! This seems to occur when the last statement of a query is empty, as conn.execute("") triggers this, however, conn.execute("select 1 -- comment") does not.
Looking at the sqlite docs: (https://www.sqlite.org/c3ref/prepare.html) it appears that we aren't handling the cases where the query is empty or a complete comment.

summary:

• successfully reproduced your example
• reproduced "comments in normal query" via:

select 1; -- comment

• failed to reproduce "comments in normal query" via:

-- comment
select 1

select 1;
-- comment
select 1;

• found a new case:

use sqlx::{Connect, Executor};
use sqlx::sqlite::SqliteConnection;

#[async_std::main]
async fn main() {
    let mut conn = SqliteConnection::connect("sqlite::memory:").await.unwrap();
    conn.execute("").await.unwrap();
}

• completed diagnosis of bug

conclusion:
As a temporary workaround while we work on fixing this, you can write your queries such that:

1. They aren't just a comment
2. There is no ; after the final statement in a query OR there is no comment after the final statement in a query (statement -- comment is fine, statement; is fine, statement; -- comment is bugged).

[mehcode]

@izik1 Thanks for the detailed investigation.

---

@PonasKovas This should be fixed on master. If you don't mind trying it out when you have a moment to see if it does indeed fix your case; that would help validate the fix.

[PonasKovas]

@mehcode Yep, everything woks now, thanks.