Summary

This PR enhances the #[cgp_component, #[cgp_provider] and #[cgp_context] macros, so that the attribute arguments can be simplified.

#[cgp_component]

If the user only wants to specify the provider key, the expression can be simplified from #[cgp_component{ provider: ProviderName } to #[cgp_component(ProviderName].

#[cgp_provider]

If no attribute is provided, the component name is deduced from the provider name, in the format "{ProviderName}Component"

#[cgp_context]

If no attribute is provided, the context provider name is deduced from the context struct name, in the format "{ContextName}Components".

Example

Prior to this, the macro requires at least the component name and the provider name to be specified, such as:

#[cgp_component {
    provider: Greeter,
}]
pub trait CanGreet {
    fn greet(&self);
}

#[cgp_new_provider(GreeterComponent)]
impl<Context> Greeter<Context> for GreetHello {
    fn greet(&self) {
        println!("Hello, World!");
    }
}

#[cgp_context(MyContextComponents)]
pub struct MyContext;

delegate_components! {
    MyContextComponents {
        GreeterComponent: GreetHello,
    }
}

After this PR, the names can omitted and simplified to:

#[cgp_component(Greeter)]
pub trait CanGreet {
    fn greet(&self);
}

#[cgp_new_provider]
impl<Context> Greeter<Context> for GreetHello {
    fn greet(&self) {
        println!("Hello, World!");
    }
}

#[cgp_context]
pub struct MyContext;

delegate_components! {
    MyContextComponents {
        GreeterComponent: GreetHello,
    }
}