Enabled required features from examples automatically

[DaAlbrecht]

Objective

Enable the required features from examples automatically. If all examples should be built/checked, enable --all-features.

Testing

❯ bevy run --example web_asset -v
debug: running: `cargo metadata --format-version 1`
debug: enabling required_features: ["https"], for example: web_asset
debug: running: `cargo run --example web_asset --features https --profile dev`
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.14s

❯ bevy build --example web_asset -v
debug: running: `cargo metadata --format-version 1`
debug: enabling required_features: ["https"], for example: web_asset
debug: running: `cargo build --example web_asset --features https --profile dev`
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.14s

Note

Building and lining all examples does not work until #629

Closes #622

[alice-i-cecile]

Yay! That's very nice.

[BD103]

I haven't had a chance to look over the code yet, but could you please add some basic docs on this feature? I don't want to diverge from Cargo without documenting it :)

[DaAlbrecht]

I haven't had a chance to look over the code yet, but could you please add some basic docs on this feature? I don't want to diverge from Cargo without documenting it :)

yea good point! Alice mentioned she would like a yes/no prompt i think that would be self documenting and no longer silently diverge from cargo what do you think?

[BD103]

yea good point! Alice mentioned she would like a yes/no prompt i think that would be self documenting and no longer silently diverge from cargo what do you think?

While I think a prompt would be good with users who are unaware of the feature, I think it would also be really annoying for users who are aware and actively want the example's required features to be enabled. Maybe a good alternative would be switching the enabling required_features log message from debug!() to info!()?

But I also don't think that replaces having documentation on our website. A user shouldn't have to install the CLI or read the changelog to see all the features supported by a program. I can draft up something if you want me to!

[DaAlbrecht]

I can draft up something if you want me to!

I added a section but I always appreciate your docs/writing style, so feel free to delete it ^^