Type mismatch between Field and Ref

[willium]

I've using Mosaic from within TypeScript so I authored some type declarations.

I don't stand by their correctness, but in the process of doing so, I noticed a type mismatch that might lead to bugs.

Coordinator calls a client's fields() method, and expects the client to return an array of objects with roughly this type:

	export interface Field {
		table: string;
		column: string;
		stats?: Set<keyof typeof Stats> | (keyof typeof Stats)[];
	}

As you can see here:

mosaic/packages/core/src/Coordinator.js

Lines 138 to 141 in 04d68e1

	const fields = client.fields();
	if (fields?.length) {
	client.fieldInfo(await queryFieldInfo(this, fields));
	}

and here:

mosaic/packages/core/src/util/field-info.js

Lines 26 to 34 in 04d68e1

	export async function queryFieldInfo(mc, fields) {
	if (fields.length === 1 && `${fields[0].column}` === '*') {
	return getTableInfo(mc, fields[0].table);
	} else {
	return (await Promise
	.all(fields.map(f => getFieldInfo(mc, f))))
	.filter(x => x);
	}
	}

and here:

mosaic/packages/core/src/util/field-info.js

Lines 71 to 80 in 04d68e1

	async function getTableInfo(mc, table) {
	const result = await mc.query(`DESCRIBE ${asRelation(table)}`);
	return Array.from(result).map(desc => ({
	table,
	column: desc.column_name,
	sqlType: desc.column_type,
	type: jsType(desc.column_type),
	nullable: desc.null === 'YES'
	}));
	}

---

However, in some of the clients, like Table, the fields method implementation looks like this:

mosaic/packages/inputs/src/Table.js

Lines 90 to 92 in 04d68e1

	fields() {
	return this.columns.map(name => column(this.from, name));
	}

which uses this method on Ref that returns a new instance of Ref:

mosaic/packages/sql/src/ref.js

Lines 94 to 100 in 04d68e1

	export function column(table, column = null) {
	if (arguments.length === 1) {
	column = table;
	table = null;
	}
	return new Ref(table, column);
	}

However, Ref does not require that the table and column properties are non-null, as you can see in the toString() method:

mosaic/packages/sql/src/ref.js

Lines 27 to 36 in 04d68e1

	toString() {
	const { table, column } = this;
	if (column) {
	const col = column.startsWith('*') ? column : `"${column}"`;
	return `${table ? `${quoteTableName(table)}.` : ''}${col}`;
	} else {
	return table ? quoteTableName(table) : 'NULL';
	}
	}
	}

So, in cases like this where we use a Ref as if it implemented Field without any checks, we might end up using null as if it were a string.