feat(macros.rs): add macro to get version from Cargo.toml

examples/09_AutoVersion.rs

@@ -1,19 +1,28 @@
+#[macro_use]
 extern crate clap;
 
 use clap::App;
 
 fn main() {
     // You can have clap pull the application version directly from your Cargo.toml starting with
-    // clap v0.4.14 on crates.io (or master#a81f915 on github)
+    // clap v0.4.14 on crates.io (or master#a81f915 on github). Using Rust's env! macro like this:
+    //
+    // let version = format!("{}.{}.{}{}",
+    //                  env!("CARGO_PKG_VERSION_MAJOR"),
+    //                  env!("CARGO_PKG_VERSION_MINOR"),
+    //                  env!("CARGO_PKG_VERSION_PATCH"),
+    //                  option_env!("CARGO_PKG_VERSION_PRE").unwrap_or("")); 
+    //
+    // Starting from v0.6.6 on crates.io you can also use the crate_version!() macro instead of 
+    // manually using the env!() macros. Under the hood, the macro uses this exact method to get
+    // the version.
     //
     // Thanks to https://github.com/jhelwig for pointing this out
-    let version = format!("{}.{}.{}{}",
-                          env!("CARGO_PKG_VERSION_MAJOR"),
-                          env!("CARGO_PKG_VERSION_MINOR"),
-                          env!("CARGO_PKG_VERSION_PATCH"),
-                          option_env!("CARGO_PKG_VERSION_PRE").unwrap_or(""));
-
-    let matches = App::new("myapp").about("does awesome things").version(&version[..]).get_matches();
+    let matches = App::new("myapp")
+                      .about("does awesome things")
+                      // use crate_version! to pull the version number
+                      .version(&crate_version!()[..])
+                      .get_matches();
 
     // running the this app with the -v or --version will display whatever version is in your
     // Cargo.toml, the default being: myapp 0.0.1

src/macros.rs

@@ -382,3 +382,27 @@ macro_rules! arg_enum {
 		}
 	};
 }
+
+/// Allows you pull the version for an from your Cargo.toml as MAJOR.MINOR.PATCH_PKGVERSION_PRE
+///
+/// # Example
+/// ```no_run
+/// # #[macro_use]
+/// # extern crate clap;
+/// # use clap::App;
+/// # fn main() {
+/// 	let m = App::new("app")
+///					.version(crate_version!())
+///					.get_matches();
+/// # }
+/// ```
+#[macro_export]
+macro_rules! crate_version {
+	() => {
+		format!("{}.{}.{}{}",
+      		env!("CARGO_PKG_VERSION_MAJOR"),
+      		env!("CARGO_PKG_VERSION_MINOR"),
+      		env!("CARGO_PKG_VERSION_PATCH"),
+      		option_env!("CARGO_PKG_VERSION_PRE").unwrap_or(""))
+	}
+}