New features: "rtu-sync", "tcp-sync", "rtu-server"

Split feature "sync" into "rtu-sync" and "tcp-sync". This is required
to avoid an unused tokio-serial dependency that is only needed for
"rtu-sync" but not for "rtu" (async).

CHANGELOG.md

@@ -7,6 +7,9 @@
 
 ### Breaking Changes
 
+- Features: Added "rtu-sync" as a replacement and superset of "rtu" and "sync"
+- Features: Added "tcp-sync" as a replacement and superset of "tcp" and "sync"
+- Features: Added "rtu-server" as a replacement and superset of "rtu" and "server"
 - Server: Removed inconsistent `server::*` re-exports from `prelude::tcp`
 
 ## v0.6.1 (2023-02-13)

Cargo.toml

@@ -31,28 +31,42 @@ socket2 = { version = "0.4.7", optional = true, default-features = false }
 tokio = { version = "1.25.0", default-features = false }
 # Disable default-features to exclude unused dependency on libudev
 tokio-serial = { version = "5.4.4", optional = true, default-features = false }
-tokio-util = { version = "0.7.7", features = ["codec"] }
+tokio-util = { version = "0.7.7", default-features = false, features = [
+    "codec",
+] }
 
 [dev-dependencies]
 env_logger = "0.10.0"
 futures = "0.3.26"
-tokio = { version = "1.25.0", features = ["net", "macros", "io-util", "rt", "time"] }
+tokio = { version = "1.25.0", default-features = false, features = ["macros", "rt-multi-thread", "time"] }
+tokio-serial = { version = "5.4.4", default-features = false }
 
 [features]
-default = ["tcp", "rtu"]
-rtu = ["tokio-serial", "futures-util/sink"]
+default = ["rtu", "tcp"]
+rtu = ["futures-util/sink"]
 tcp = ["tokio/net", "futures-util/sink"]
-sync = ["tokio/rt"]
-server = ["futures", "socket2/all", "tokio/macros", "tokio/rt", "tokio/rt-multi-thread"]
-tcp-server-unstable = ["tcp", "server"]
+# The internal feature "sync" has no effect when used alone.
+# It is always enabled together with "rtu-sync" or "tcp-sync".
+sync = []
+rtu-sync = ["rtu", "sync", "dep:tokio-serial"]
+tcp-sync = ["tcp", "sync"]
+server = ["dep:futures"]
+rtu-server = ["rtu", "server", "tokio/macros", "dep:tokio-serial"]
+tcp-server-unstable = [
+    "tcp",
+    "server",
+    "socket2/all",
+    "tokio/macros",
+    "tokio/rt-multi-thread",
+]
 
 [badges]
 maintenance = { status = "actively-developed" }
 
 [[example]]
 name = "rtu-client-sync"
 path = "examples/rtu-client-sync.rs"
-required-features = ["rtu", "sync"]
+required-features = ["rtu-sync"]
 
 [[example]]
 name = "rtu-client"
@@ -62,7 +76,7 @@ required-features = ["rtu"]
 [[example]]
 name = "rtu-server"
 path = "examples/rtu-server.rs"
-required-features = ["rtu", "server"]
+required-features = ["rtu-server"]
 
 [[example]]
 name = "rtu-server-address"
@@ -77,7 +91,7 @@ required-features = ["tcp"]
 [[example]]
 name = "tcp-client-sync"
 path = "examples/tcp-client-sync.rs"
-required-features = ["tcp", "sync"]
+required-features = ["tcp-sync"]
 
 [[example]]
 name = "tcp-client"

README.md

@@ -39,25 +39,43 @@ Add this to your `Cargo.toml`:
 tokio-modbus = "*"
 ```
 
-If you like to use Modbus TCP only:
+### Cargo Features
+
+- `"rtu"`: Asynchronous RTU client (default)
+- `"tcp"`: Asynchronous TCP client (default)
+- `"rtu-sync`: Synchronous RTU client
+- `"tcp-sync"`: Synchronous RTU client (default)
+- `"rtu-server"`: (Asynchronous) RTU server
+- `"tcp-server-unstable"`: (Asynchronous) TCP server (experimental)
+
+#### Examples
+
+If you only need an asynchronous TCP client add the following line to your Cargo.toml file:
 
 ```toml
 [dependencies]
 tokio-modbus = { version = "*", default-features = false, features = ["tcp"] }
 ```
 
-If you like to use Modbus RTU only:
+For an asynchronous RTU client:
 
 ```toml
 [dependencies]
 tokio-modbus = { version = "*", default-features = false, features = ["rtu"] }
 ```
 
-If you like to build a TCP server:
+For an RTU server:
+
+```toml
+[dependencies]
+tokio-modbus = { version = "*", default-features = false, features = ["rtu-server"] }
+```
+
+For a TCP server:
 
 ```toml
 [dependencies]
-tokio-modbus = { version = "*", default-features = false, features = ["tcp", "server"] }
+tokio-modbus = { version = "*", default-features = false, features = ["tcp-server-unstable"] }
 ```
 
 ## Examples

src/client/mod.rs

@@ -12,15 +12,15 @@ use async_trait::async_trait;
 
 use crate::{frame::*, slave::*};
 
-#[cfg(feature = "sync")]
-pub mod sync;
-
 #[cfg(feature = "rtu")]
 pub mod rtu;
 
 #[cfg(feature = "tcp")]
 pub mod tcp;
 
+#[cfg(feature = "sync")]
+pub mod sync;
+
 /// Transport independent asynchronous client trait
 #[async_trait]
 pub trait Client: SlaveContext + Send + Debug {

src/client/sync/mod.rs

@@ -3,15 +3,12 @@
 
 //! Synchronous Modbus client
 
-// TODO: Add missing documentation
 #![allow(missing_docs)]
 
-/// RTU client connections
-#[cfg(feature = "rtu")]
+#[cfg(feature = "rtu-sync")]
 pub mod rtu;
 
-/// TCP client connections
-#[cfg(feature = "tcp")]
+#[cfg(feature = "tcp-sync")]
 pub mod tcp;
 
 use super::{

src/lib.rs

@@ -5,13 +5,16 @@
 #![warn(rust_2021_compatibility)]
 #![warn(missing_debug_implementations)]
 #![warn(unreachable_pub)]
+#![warn(clippy::cast_lossless)]
+// TODO (v0.6): Decorate functions with #[must_use]
+//#![warn(clippy::must_use_candidate)]
 #![cfg_attr(not(test), warn(unsafe_code))]
 #![warn(clippy::all)]
 #![warn(clippy::cast_lossless)]
 #![warn(clippy::explicit_deref_methods)]
 #![warn(clippy::explicit_into_iter_loop)]
 #![warn(clippy::explicit_iter_loop)]
-// TODO (v0.6): Decorate functions with #[must_use]
+// TODO: Decorate functions with #[must_use]
 //#![warn(clippy::must_use_candidate)]
 #![cfg_attr(not(test), warn(clippy::panic_in_result_fn))]
 #![cfg_attr(not(test), warn(clippy::cast_possible_truncation))]

src/server/mod.rs

@@ -6,7 +6,7 @@
 // TODO: Add missing documentation
 #![allow(missing_docs)]
 
-#[cfg(feature = "rtu")]
+#[cfg(feature = "rtu-server")]
 pub mod rtu;
 
 #[cfg(feature = "tcp-server-unstable")]