WIP: PoC support for Valuable

Cargo.toml

@@ -19,6 +19,7 @@ rust-version = "1.75.0"
 default = ["tracing-log", "metrics"]
 # Enables support for exporting OpenTelemetry metrics
 metrics = ["opentelemetry/metrics", "smallvec"]
+valuable = ["dep:valuable", "tracing-core/valuable"]
 
 [dependencies]
 opentelemetry = { version = "0.31.0", default-features = false, features = [
@@ -37,6 +38,8 @@ smallvec = { version = "1.0", optional = true }
 # Fix minimal-versions
 lazy_static = { version = "1.0.2", optional = true }
 
+valuable = { version = "0.1.1", optional = true }
+
 [dev-dependencies]
 criterion = { version = "0.5.1", default-features = false, features = [
     "html_reports",
@@ -79,6 +82,7 @@ bench = false
 
 [lints.rust]
 unnameable_types = "warn"
+unexpected_cfgs = { level = "warn", check-cfg = ["cfg(tracing_unstable)"] }
 
 [[bench]]
 name = "trace"

src/layer.rs

@@ -35,6 +35,7 @@ const SPAN_EVENT_COUNT_FIELD: &str = "otel.tracing_event_count";
 const EVENT_EXCEPTION_NAME: &str = "exception";
 const FIELD_EXCEPTION_MESSAGE: &str = "exception.message";
 const FIELD_EXCEPTION_STACKTRACE: &str = "exception.stacktrace";
+const FIELD_EXCEPTION_TYPE: &str = "exception.type";
 
 /// An [OpenTelemetry] propagation layer for use in a project that uses
 /// [tracing].
@@ -246,6 +247,45 @@ struct SpanEventVisitor<'a, 'b> {
 }
 
 impl field::Visit for SpanEventVisitor<'_, '_> {
+    #[cfg(all(tracing_unstable, feature = "valuable"))]
+    #[cfg_attr(docsrs, doc(cfg(all(tracing_unstable, feature = "valuable"))))]
+    fn record_value(&mut self, field: &field::Field, value: valuable::Value<'_>) {
+        match field.name() {
+            "message" => self.event_builder.name = format!("{value:?}").into(),
+            "error" if self.event_builder.name.is_empty() => {
+                if self.sem_conv_config.error_events_to_status {
+                    self.span_builder_updates
+                        .get_or_insert_with(SpanBuilderUpdates::default)
+                        .status
+                        .replace(otel::Status::error(format!("{value:?}")));
+                }
+                if self.sem_conv_config.error_events_to_exceptions {
+                    self.event_builder.name = EVENT_EXCEPTION_NAME.into();
+                    self.event_builder
+                        .attributes
+                        .push(KeyValue::new(FIELD_EXCEPTION_MESSAGE, format!("{value:?}")));
+
+                    let error_type = match value {
+                        valuable::Value::Structable(s) => s.definition().name().to_string(),
+                        valuable::Value::Enumerable(s) => s.definition().name().to_string(),
+                        _ => "unknown".to_string(),
+                    };
+                    self.event_builder
+                        .attributes
+                        .push(KeyValue::new(FIELD_EXCEPTION_TYPE, error_type));
+                } else {
+                    self.event_builder
+                        .attributes
+                        .push(KeyValue::new("error", format!("{value:?}")));
+                }
+            }
+            // Skip fields that are actually log metadata that have already been handled
+            #[cfg(feature = "tracing-log")]
+            name if name.starts_with("log.") => (),
+            _ => self.record_debug(field, &value),
+        }
+    }
+
     /// Record events on the underlying OpenTelemetry [`Span`] from `bool` values.
     ///
     /// [`Span`]: opentelemetry::trace::Span