Constructors for Pool and connection types to get configuration from environment

[abonander]

TODO: fill this out when I'm not on a phone

[mehcode]

I think we were discussing something to this effect (not locked in to the naming):

// Equivalent to: Connection::open(env::var("DATABASE_URL").unwrap_or_default())

Connection::open_from_env()

// Equivalent to: Pool::new(env::var("DATABASE_URL").unwrap_or_default())

Pool::from_env()

// Equivalent to: Pool::builder().build(env::var("DATABASE_URL").unwrap_or_default())

Pool::builder().build_from_env()

[tim-harding]

Started jamming on this a bit tonight, hoping to have some updates early next week or sooner.

[nsanta]

Hi. I started to work on this task today and I have two questions:

• Why Connection::open_from_env() should use open since is deprecated?
• Why not use the env DATABASE_URL as the default/fallback value instead of create new functions?

[abonander]

That comment was outdated. The new method I believe should be on the Connect trait now and be called connect_with_env().

Why not use the env DATABASE_URL as the default/fallback value instead of create new functions?

Do you mean for Pool::builder().build_from_env()? I feel like going through the builder is already pretty explicit, might as well be explicit where the database URL is coming from.

[abonander]

However, I think we need to discuss this a bit more as we want to combine this with #78, however that implies that the individual connection type defines what parameters it tries to get from the environment; maybe instead the new method on Connect should look something like this:

fn url_from_env() -> crate::Result<Url>;

Where the implementation populates as many parts of the URL as it can (username, password, host, port, database) with information from the environment and then uses published defaults for the rest.

[nsanta]

I like the second approach @abonander. Thank you!

[mehcode]

Marking this as blocked on doing #174 first

[mehcode]

We now have Connect::connect_with(options) and Connect::connect(url).

I can see adding Connect::connect_from_env().

We should probably also add Pool::new_with(options) and PoolBuilder::build_with(options).