Add TYPE_NAME constant to messages and make error fields public (#277)

rosidl_generator_rs/resource/msg_rmw.rs.em

@@ -102,6 +102,7 @@ impl rosidl_runtime_rs::Message for @(type_name) {
 }
 
 impl rosidl_runtime_rs::RmwMessage for @(type_name) where Self: Sized {
+  const TYPE_NAME: &'static str = "@(package_name)/@(subfolder)/@(type_name)";
   fn get_type_support() -> libc::uintptr_t {
     // SAFETY: No preconditions for this function.
     unsafe { rosidl_typesupport_c__get_message_type_support_handle__@(package_name)__@(subfolder)__@(type_name)() }

rosidl_runtime_rs/src/sequence.rs

@@ -75,8 +75,10 @@ pub struct BoundedSequence<T: SequenceAlloc, const N: usize> {
 /// Error type for [`BoundedSequence::try_new()`].
 #[derive(Debug)]
 pub struct SequenceExceedsBoundsError {
-    len: usize,
-    upper_bound: usize,
+    /// The actual length the sequence would have after the operation.
+    pub len: usize,
+    /// The upper bound on the sequence length.
+    pub upper_bound: usize,
 }
 
 /// A by-value iterator created by [`Sequence::into_iter()`] and [`BoundedSequence::into_iter()`].

rosidl_runtime_rs/src/string.rs

@@ -102,8 +102,10 @@ pub struct BoundedWString<const N: usize> {
 /// Error type for [`BoundedString::try_from()`] and [`BoundedWString::try_from()`].
 #[derive(Debug)]
 pub struct StringExceedsBoundsError {
-    len: usize,
-    upper_bound: usize,
+    /// The actual length the string would have after the operation.
+    pub len: usize,
+    /// The upper bound on the string length.
+    pub upper_bound: usize,
 }
 
 // ========================= impls for String and WString =========================

rosidl_runtime_rs/src/traits.rs

@@ -38,6 +38,9 @@ pub trait SequenceAlloc: Sized {
 ///
 /// User code never needs to call this trait's method, much less implement this trait.
 pub trait RmwMessage: Clone + Debug + Default + Send + Sync + Message {
+    /// A string representation of this message's type, e.g. "geometry_msgs/msg/Twist"
+    const TYPE_NAME: &'static str;
+
     /// Get a pointer to the correct `rosidl_message_type_support_t` structure.
     fn get_type_support() -> libc::uintptr_t;
 }