You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: alter_source_column.rs
    path of file: ./repos/risingwave/src/frontend/src/handler
    
    the code of the file until where you have to start completion: // Copyright 2024 RisingWave Labs
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use itertools::Itertools;
use pgwire::pg_response::{PgResponse, StatementType};
use risingwave_common::catalog::ColumnId;
use risingwave_connector::source::{extract_source_struct, SourceEncode, 
    
    async fn test_alter_source_column_handler() {
        let frontend = LocalFrontend::new(Default::default()).await;
        let session = frontend.session_ref();
        let schema_path = SchemaPath::Name(DEFAULT_SCHEMA_NAME);

        let sql = r#"create source s (v1 int) with (
            connector = 'kafka',
            topic = 'abc',
            properties.bootstrap.server = 'localhost:29092',
          ) FORMAT PLAIN ENCODE JSON;"#;

        frontend.run_sql(sql).await.unwrap();

        let get_source = || {
            let catalog_reader = session.env().catalog_reader().read_guard();
            catalog_reader
                .get_source_by_name(DEFAULT_DATABASE_NAME, schema_path, "s")
                .unwrap()
                .0
                .clone()
        };

        let source = get_source();
        let columns: HashMap<_, _> = source
            .columns
            .iter()
            .map(|col| (col.name(), (col.data_type().clone(), col.column_id())))
            .collect();

        let sql = "alter source s add column v2 varchar;";
        frontend.run_sql(sql).await.unwrap();

        let altered_source = get_source();

        let altered_columns: HashMap<_, _> = altered_source
            .columns
            .iter()
            .map(|col| (col.name(), (col.data_type().clone(), col.column_id())))
            .collect();

        // Check the new column.
        assert_eq!(columns.len() + 1, altered_columns.len());
        assert_eq!(altered_columns["v2"].0, DataType::Varchar);

        // Check the old columns and IDs are not changed.
        assert_eq!(columns["v1"], altered_columns["v1"]);

        // Check version
        assert_eq!(source.version + 1, altered_source.version);

        // Check definition
        let altered_sql = r#"CREATE SOURCE s (v1 INT, v2 CHARACTER VARYING) WITH (connector = 'kafka', topic = 'abc', properties.bootstrap.server = 'localhost:29092') FORMAT PLAIN ENCODE JSON"#;
        assert_eq!(altered_sql, altered_source.definition);
    }