Fix bug on filter for empty group

[code28]

When using the QueryBuilder and a filter group with or, the resulting SQL statement is incorrect, if no filters are provided.

Since this is a mix between an issue and a proposition of a solution, I'm first describing the issue:

Steps to reproduce

User.query(on: req).group(.or) { query in
    // No filters here...
}.all()

Expected behavior

No filters, so no restrictions on the query, so the statement should be:
SELECT * FROM "User" WHERE [].

Actual behavior

I get the following error: [ ERROR ] SQLiteError.error: near ")": syntax error (SQLiteStatement.swift:15), caused by the SQL statement SELECT * FROM "User" WHERE () [].

My solution

Since Fluent 4 seems to work quite differently, I chose to apply this PR on version 3. This feels a bit "hacky", and I'm not sure if it should be at another point inside the query building stack, but this is a solution to the error.

But... why?

Why should you use .group without any filters? Because sometimes you loop over an array of filters, which could be empty.

[tanner0101]

This fix LGTM, thanks. To get CI passing, we need to change this line in circle CI config to checkout branch 1 not master: https://github.com/vapor/fluent/blob/3/circle.yml#L42

Additionally, could you open an issue against https://github.com/vapor/fluent-kit to ensure we fix this in the Fluent 4 code, too?

[code28]

This fix LGTM, thanks. To get CI passing, we need to change this line in circle CI config to checkout branch 1 not master: https://github.com/vapor/fluent/blob/3/circle.yml#L42

Do you mean branch 3 or indeed 1? And I assume, it should be changed for mysql and sqlite as well..?

Additionally, could you open an issue against https://github.com/vapor/fluent-kit to ensure we fix this in the Fluent 4 code, too?

Sure!

[tanner0101]

PostgreSQL was a new package for Vapor 3, so its stable version is 1.0: https://github.com/vapor/fluent-postgresql/tree/1

[code28]

PostgreSQL was a new package for Vapor 3, so its stable version is 1.0: https://github.com/vapor/fluent-postgresql/tree/1

Oops, that one was stupid, sorry. Obviously didn't read the circle.yml correctly... 🙈

[penny-coin]

Hey @code28, you just merged a pull request, have a coin!

You now have 1 coins.

[tanner0101]

Thanks :)