Add test that structure is as expected

Author: nnmm

rclrs/src/dynamic_message.rs

@@ -257,6 +257,11 @@ impl DynamicMessageMetadata {
         let pkg = DynamicMessagePackage::new(package_name)?;
         pkg.message_metadata(type_name)
     }
+
+    /// Returns a description of the message structure.
+    pub fn structure(&self) -> &MessageStructure {
+        &self.structure
+    }
 }
 
 #[cfg(test)]

rclrs_tests/Cargo.toml

@@ -8,11 +8,11 @@ edition = "2021"
 path = "src/lib.rs"
 
 [dependencies]
-anyhow = {version = "1", features = ["backtrace"]}
-test_msgs = {version = "*"}
+test_msgs = "*"
 
 [dependencies.rclrs]
 version = "*"
+features = ["dyn_msg"]
 
 [dependencies.rosidl_runtime_rs]
 version = "*"

rclrs_tests/build.rs

@@ -0,0 +1,19 @@
+use std::env;
+
+const ROS_DISTRO: &str = "ROS_DISTRO";
+
+fn get_env_var_or_abort(env_var: &'static str) -> String {
+    if let Ok(value) = env::var(env_var) {
+        value
+    } else {
+        panic!(
+            "{} environment variable not set - please source ROS 2 installation first.",
+            env_var
+        );
+    }
+}
+
+fn main() {
+    let ros_distro = get_env_var_or_abort(ROS_DISTRO);
+    println!("cargo:rustc-cfg=ros_distro=\"{ros_distro}\"");
+}