Add support for hash and url configs to be used in connected_to

[gmcgibbon]

Summary

I noticed when using the new connection switching API, if I use a string database name, it bubbles down to this connection resolution method which thinks strings are database URLs. Do we want to support URLs, or is this acceptable behaviour? If not, we should make DatabaseConfig#spec_name return a symbol instead of a string.

[gmcgibbon]

r? @eileencodes
cc @rafaelfranca

[eileencodes]

Right now connects_to wraps around establish_connection so it should behave the same exact way.

>> ActiveRecord::Base.establish_connection "primary"
ActiveRecord::AdapterNotSpecified: database configuration does not specify adapter
	from (irb):14

>> ActiveRecord::Base.connects_to database: { :writing => "primary" }
ActiveRecord::AdapterNotSpecified: database configuration does not specify adapter
	from (irb):15

To me a string that's not a URL causing an error is the correct behavior. I do think however this error message could be improved to note it expected a database URL instead.

[gmcgibbon]

Ok, I assumed it was different because you can't currently use a connection hash because of this to_sym call. What do you think of DatabaseConfig#spec_name returning a symbol then? I can also improve the error in another PR.

[eileencodes]

Ohhhh I see - I was thinking about connects_to. Yes in that case we should remove the to_sym call in connected_to. That was a mistake on my part. Can you update this PR to remove that and add a test for a URL configuration? Thanks!

[eileencodes]

The underlying problem is that there are a billion ways to make a configuration and connect to the database. Take a look at this test https://github.com/rails/rails/blob/master/activerecord/test/cases/connection_adapters/merge_and_resolve_default_url_config_test.rb and you'll get an idea of some of the possible scenarios. We may eventually want to say some of these are not going to be possible with a multi-db application but I don't think we're there yet. For example, I'm not sure how a DATABASE_URL would work with multiple databases - since you can only pass one at a time.

[gmcgibbon]

Done! I added a test for both hash configs and URLs since they both fail on master.

[gmcgibbon]

I'm not sure how I feel about this. Should we try to lookup the config to store the handler with a symbol key and fallback to this behaviour if its not mentioned in database.yml?

[eileencodes]

Oh 💩 it just occurred to me this isn't going to work. It's fine if it's a symbol but what would the handler be if it was a url? We definitely don't want the handler to be postgres://blah so I think we need to change connects to to take a role and a database at the same time and only if it's a symbol use the database name as a handler. Thoughts?

[gmcgibbon]

Yeah, I think if we always lookup handlers using symbols, that makes the most sense. Does it make sense to always use roles for handler lookup or do we need to still try using the database spec/env/config/url/??? for legacy support?

[eileencodes]

We need the handler/role for when you're connected already and we need the database for connecting to a database that your model doesn't always want to be connected to (for example, readonly_slow). Role should always be symbol. I'm not sure what legacy support we would need? This is a new method so we can change it until 6 is released.

I've been thinking about this and I think we should either accept a symbol or a hash for the database option. If you need to pass a string then you need to also pass a role / name / handler with it.

ActiveRecord::Base.connected_to(database: { my_url_db: "postgres://blah" }) do
  # do something with this db
end

Otherwise a symbol is expected.

[gmcgibbon]

I changed the logic around to use database if its a symbol or role if it isn't. That should solve the issue AFAICT.

[gmcgibbon]

I've been thinking about this and I think we should either accept a symbol or a hash for the database option. If you need to pass a string then you need to also pass a role / name / handler with it.

I've refactored the method to behave this way for both URLs and config hashes. WDYT?

[eileencodes]

We need the handler/role for when you're connected already and we need the database for connecting to a database that your model doesn't always want to be connected to (for example, readonly_slow). Role should always be symbol. I'm not sure what legacy support we would need? This is a new method so we can change it until 6 is released.

I've been thinking about this and I think we should either accept a symbol or a hash for the database option. If you need to pass a string then you need to also pass a role / name / handler with it.

ActiveRecord::Base.connected_to(database: { my_url_db: "postgres://blah" }) do
  # do something with this db
end

Otherwise a symbol is expected.

[eileencodes]

You have a typo in handler 😄

[gmcgibbon]

🤦‍♂️

[eileencodes]

This looks great! Thank you!

[bogdanvlviv]

Great addition. Thank you! Just want to note that we don't add changelog entries about complementing features that haven't been released.