aws_config default provider (incorrectly?) requires rustls

[ereOn]

I am in the process of cleaning up the dependency graph of our monorepo, and I noticed we are still pulling hyper 0.14 due to aws_config still referencing it.

I understand it still references it mainly through rustls and possibly also the "hyper 0.14 connector" facility.

Looking through the code I noticed here that the default provider seems to be gated for the rustls feature.

#[cfg(feature = "rustls")]
/// Default Credentials Provider chain
///
/// The region from the default region provider will be used
pub async fn default_provider() -> impl ProvideCredentials {
    DefaultCredentialsChain::builder().build().await
}

This seems to be confirmed by the comment here too:

/// Creates a `DefaultCredentialsChain`
    ///
    /// ## Panics
    /// This function will panic if no connector has been set or the `rustls`
    /// feature has been disabled.
    pub async fn build(self) -> DefaultCredentialsChain {
        let region = match self.region_override {
            Some(provider) => provider.region().await,
            None => self.region_chain.build().region().await,
        };

        let conf = self.conf.unwrap_or_default().with_region(region);

        let env_provider = EnvironmentVariableCredentialsProvider::new_with_env(conf.env());
        let profile_provider = self.profile_file_builder.configure(&conf).build();
        let web_identity_token_provider = self.web_identity_builder.configure(&conf).build();
        let imds_provider = self.imds_builder.configure(&conf).build();
        let ecs_provider = self.ecs_builder.configure(&conf).build();

        let provider_chain = CredentialsProviderChain::first_try("Environment", env_provider)
            .or_else("Profile", profile_provider)
            .or_else("WebIdentityToken", web_identity_token_provider)
            .or_else("EcsContainer", ecs_provider)
            .or_else("Ec2InstanceMetadata", imds_provider);

        DefaultCredentialsChain { provider_chain }
    }

Looking a all the referenced providers, it seems that none of those actually depends on rustls so I'm not sure whether the feature-gate is still legitimate or if I'm missing something obvious.

Also, if the rustls feature-gate is still legitimate, the comment seems to indicate that one might avoid the panic by specifying a connector. Is there any example of that ?

Thank you and sorry if this turns out to be a false positive.

[aajtodd]

This is a bit convoluted and I'm probably missing some historical context but effectively this boils down to the default HTTP client plugin from aws-smithy-runtime requires both the tls-rustls and connector-hyper-0-14-x which are both enabled by the rustls feature of aws-config. So in other words this rustls feature flag is being used as a proxy for enabling a default HTTP client supplied by the runtime (which is required for several of the credential providers of the default chain to work).

This should eventually be addressed by #1925