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refactor: use cfg-aliases for feature flags #3865

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77 changes: 77 additions & 0 deletions build.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,77 @@
fn main() {
// Add to the list of expected config names and values that is used when checking the reachable
// cfg expressions with the unexpected_cfgs lint.
//
// See https://doc.rust-lang.org/cargo/reference/build-scripts.html#rustc-check-cfg
println!("cargo:rustc-check-cfg=cfg(http1)");
println!("cargo:rustc-check-cfg=cfg(http2)");
println!("cargo:rustc-check-cfg=cfg(client)");
println!("cargo:rustc-check-cfg=cfg(server)");
println!("cargo:rustc-check-cfg=cfg(ffi)");
println!("cargo:rustc-check-cfg=cfg(full)");
println!("cargo:rustc-check-cfg=cfg(nightly)");
println!("cargo:rustc-check-cfg=cfg(runtime)"); // TODO evaluate if this is needed (see below)
println!("cargo:rustc-check-cfg=cfg(tracing)");
println!("cargo:rustc-check-cfg=cfg(http_client)");
println!("cargo:rustc-check-cfg=cfg(http1_client)");
println!("cargo:rustc-check-cfg=cfg(http2_client)");
println!("cargo:rustc-check-cfg=cfg(http_server)");
println!("cargo:rustc-check-cfg=cfg(http1_server)");
println!("cargo:rustc-check-cfg=cfg(http2_server)");

// Add cfg flags that simplify using cfg expressions in the code. e.g. instead of
// `#[cfg(all(any(feature = "http1", feature = "http2"), feature = "server")]` you can use
// `#[cfg(http_server)]`
//
// See https://doc.rust-lang.org/cargo/reference/build-scripts.html#rustc-cfg
#[cfg(feature = "http1")]
println!("cargo:rustc-cfg=http1");

#[cfg(feature = "http2")]
println!("cargo:rustc-cfg=http2");

#[cfg(any(feature = "http1", feature = "http2"))]
println!("cargo:rustc-cfg=http");

#[cfg(feature = "client")]
println!("cargo:rustc-cfg=client");

#[cfg(feature = "server")]
println!("cargo:rustc-cfg=server");

#[cfg(feature = "ffi")]
println!("cargo:rustc-cfg=ffi");

#[cfg(feature = "full")]
println!("cargo:rustc-cfg=full");

#[cfg(feature = "nightly")]
println!("cargo:rustc-cfg=nightly");

// TODO: this feature doesn't actually exist in the cargo.toml
// this condition was added to simplify the conditions in src/mock.rs, but I'm not sure if those
// conditions were actually working as intended
// #[cfg(feature = "runtime")]
// println!("cargo:rustc-cfg=runtime");

#[cfg(feature = "tracing")]
println!("cargo:rustc-cfg=tracing");

#[cfg(all(any(feature = "http1", feature = "http2"), feature = "client"))]
println!("cargo:rustc-cfg=http_client");

#[cfg(all(feature = "http1", feature = "client"))]
println!("cargo:rustc-cfg=http1_client");

#[cfg(all(feature = "http2", feature = "client"))]
println!("cargo:rustc-cfg=http2_client");

#[cfg(all(any(feature = "http1", feature = "http2"), feature = "server"))]
println!("cargo:rustc-cfg=http_server");

#[cfg(all(feature = "http1", feature = "server"))]
println!("cargo:rustc-cfg=http1_server");

#[cfg(all(feature = "http2", feature = "server"))]
println!("cargo:rustc-cfg=http2_server");
}
8 changes: 4 additions & 4 deletions examples/hello-http2.rs
Original file line number Diff line number Diff line change
@@ -3,7 +3,7 @@

use http_body_util::Full;
use hyper::body::Bytes;
#[cfg(feature = "server")]
#[cfg(server)]
use hyper::server::conn::http2;
use hyper::service::service_fn;
use hyper::{Request, Response};
@@ -19,7 +19,7 @@ use support::TokioIo;

// An async function that consumes a request, does nothing with it and returns a
// response.
#[cfg(feature = "server")]
#[cfg(server)]
async fn hello(_: Request<hyper::body::Incoming>) -> Result<Response<Full<Bytes>>, Infallible> {
Ok(Response::new(Full::new(Bytes::from("Hello, World!"))))
}
@@ -42,7 +42,7 @@ where
}
}

#[cfg(feature = "server")]
#[cfg(server)]
#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
pretty_env_logger::init();
@@ -83,7 +83,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
}
}

#[cfg(not(feature = "server"))]
#[cfg(not(server))]
fn main() {
panic!("This example requires the 'server' feature to be enabled");
}
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