Fix: ensure transaction will have a name (#434)

Author: jessfraz

sentry-tracing/src/layer.rs

@@ -166,11 +166,24 @@ where
         let op = span.name();
         let description = description.as_deref().unwrap_or("");
 
+        // Spans don't always have a description, this ensures our data is not empty,
+        // therefore the Sentry UI will be a lot more valuable for navigating spans.
+        let transaction_name = if description.is_empty() {
+            let target = span.metadata().target();
+            if target.is_empty() {
+                op.to_string()
+            } else {
+                format!("{}::{}", target, op)
+            }
+        } else {
+            description.to_string()
+        };
+
         let parent_sentry_span = sentry_core::configure_scope(|s| s.get_span());
         let sentry_span: sentry_core::TransactionOrSpan = match &parent_sentry_span {
-            Some(parent) => parent.start_child(op, description).into(),
+            Some(parent) => parent.start_child(op, &transaction_name).into(),
             None => {
-                let ctx = sentry_core::TransactionContext::new(description, op);
+                let ctx = sentry_core::TransactionContext::new(&transaction_name, op);
                 sentry_core::start_transaction(ctx).into()
             }
         };