update "attribute not found" message to include span details

server/expression/data_store.go

@@ -27,14 +27,15 @@ func (ds AttributeDataStore) Source() string {
 
 func (ds AttributeDataStore) getFromAlias(name string) (string, error) {
 	alias, found := attributeAlias[name]
+	notMatchingErr := fmt.Errorf(`attribute "%s" not found in span "%s" (ID: %s)`, name, ds.Span.Name, ds.Span.ID.String())
 
 	if !found {
-		return "", fmt.Errorf(`attribute "%s" not found`, name)
+		return "", notMatchingErr
 	}
 
 	value := ds.Span.Attributes.Get(alias)
 	if value == "" {
-		return "", fmt.Errorf(`attribute "%s" not found`, name)
+		return "", notMatchingErr
 	}
 
 	return value, nil
@@ -45,7 +46,7 @@ func (ds AttributeDataStore) Get(name string) (string, error) {
 		// It's probably a nil span and we never got a matching selector,
 		// so instead of returning a resolution error, let's return a non-matching
 		// span error instead
-		return "", fmt.Errorf(`there are no matching spans to retrieve the attribute "%s" from`, name)
+		return "", fmt.Errorf(`there are no matching spans to retrieve the attribute "%s" from. To fix this error, create a selector matching at least one span.`, name)
 	}
 
 	value := ds.Span.Attributes.Get(name)

server/expression/executor_test.go

@@ -96,6 +96,7 @@ func TestBasicOperationExecution(t *testing.T) {
 }
 
 func TestAttributeExecution(t *testing.T) {
+	notMatchingAttributeSpanID := id.NewRandGenerator().SpanID()
 	testCases := []executorTestCase{
 		{
 			Name:       "should_get_values_from_attributes",
@@ -129,19 +130,20 @@ func TestAttributeExecution(t *testing.T) {
 			Name:                 "should_return_error_when_attribute_doesnt_exist",
 			Query:                "attr:dapr-app-id = 43",
 			ShouldPass:           false,
-			ExpectedErrorMessage: `resolution error: attribute "dapr-app-id" not found`,
+			ExpectedErrorMessage: fmt.Sprintf(`resolution error: attribute "dapr-app-id" not found in span "Span name" (ID: %s)`, notMatchingAttributeSpanID.String()),
 
 			AttributeDataStore: expression.AttributeDataStore{
 				Span: traces.Span{
-					ID: id.NewRandGenerator().SpanID(),
+					Name: "Span name",
+					ID:   notMatchingAttributeSpanID,
 				},
 			},
 		},
 		{
 			Name:                 "should_return_error_when_no_matching_spans",
 			Query:                "attr:dapr-app-id = 42",
 			ShouldPass:           false,
-			ExpectedErrorMessage: `resolution error: there are no matching spans to retrieve the attribute "dapr-app-id" from`,
+			ExpectedErrorMessage: `resolution error: there are no matching spans to retrieve the attribute "dapr-app-id" from. To fix this error, create a selector matching at least one span.`,
 
 			AttributeDataStore: expression.AttributeDataStore{
 				Span: traces.Span{