Crash unwrapping lastInsertRowid after insert when primary key may contain 0

[ewanmellor]

This bug is similar to #235 and #383, but is not fixed by the changes in #383.

The crash is the same: Query.run(query: Insert) successfully runs the insert, but sqlite3_last_insert_rowid returns 0 afterwards, which means that Connection.lastInsertRowid returns nil, and Query.run crashes when it force-unwraps that nil.

    public func run(query: Insert) throws -> Int64 {
        let expression = query.expression
        return try sync {
            try self.run(expression.template, expression.bindings)     // This succeeds
            return self.lastInsertRowid!                               // This crashes
        }
    }

This can happen in two situations according to the SQLite last_insert_row_id documentation. The first is the one that I hit:

1. The rowid is an alias for a declared integer primary key column in the table, and the insert sets the primary key to 0. As documented: "If the table has a column of type INTEGER PRIMARY KEY then that column is another alias for the rowid."
2. The table has been created with WITHOUT ROWID. As documented: "Inserts into WITHOUT ROWID tables are not recorded."

To reproduce the first crash, you can do something like this:

    let tblTest = Table("test")
    let colIndex = Expression<Int>("index")

    db.run(tblTest.create() { t in
                t.column(colIndex, primaryKey: true)
            })

    db.run(tblTest.insert(colIndex <- 0))

In #383, @stephencelis said "My take: the main insert() method shouldn't return an optional." I think that is OK, but it's at odds with the assumption inside Connection.lastInsertRowid that sqlite3_last_insert_rowid() == 0 always means "not set". I think that, since rowid can be an alias to a user-defined column, it's lastInsertRowid that is wrong, and it should always return the integer that it gets, even if that is 0.

Technically that's a breaking API change; I don't know if you have a policy about that.

[jberkel]

Fixed in 0.11.1 / #532