Using a batched junction with non-id column causes the column to not be added to the shape

[bradzacher]

creating a batched junction as follows:

field:  {
    junction: {
        uniqueKey: ['id', 'id'],
        sqlTable: 'junction',
        sqlBatch: {
            parentKey: 'junc_col',
            thisKey: 'junc_col',
            sqlJoin: (a, b) => `${a}.fielda = ${b}.fieldb`,
        },
    },
}

causes the base SQL to be generated correctly:

SELECT id as `id`,
    junc_col as `junc_col`,
FROM base

However it fails to add the junc_col to the shape definition.
This means that when it generates the batch SQL, it has no column data, so it attempts to find WHERE junc_col IN (NULL).

I'm not knowledgable enough with the codebase to be sure, but the problem is either:

• it's not adding it to the SQL AST, which means that the shape definition function doesn't know to pick it up.
  • this would make sense if it wasn't dumped into the base table SQL.
• there is an issue with the _defineShape function; it doesn't look into batched tables to determine if if it needs extra columns.

I'm leaning toward the latter as the bug - it seems to be a mismatch between the logic in the SQL stringifier and the shape definer.

[bradzacher]

note that a workaround for now is to add the required column to the alwaysFetch property.
This will cause JM to always add it correctly to the shape.

[nicoabie]

Can you come up with an example using https://github.com/join-monster/join-monster-sscce ?

Is uniqueKey: ['id', 'id'], correct?