Use default value if present

Signed-off-by: Adam Cattermole <[email protected]>

src/policy.rs

@@ -1,4 +1,4 @@
-use crate::attribute::get_attribute;
+use crate::attribute::Attribute;
 use crate::configuration::{DataItem, DataType, PatternExpression};
 use crate::envoy::{RateLimitDescriptor, RateLimitDescriptor_Entry};
 use crate::filter::http_context::Filter;
@@ -126,7 +126,25 @@ impl Policy {
                         Some(key) => key.to_owned(),
                     };
 
-                    let value = get_attribute(filter, selector_item.selector.as_str()).ok()?;
+                    let attribute_path = selector_item.path();
+                    let value = match filter.get_property(attribute_path.tokens()) {
+                        None => {
+                            debug!(
+                                "#{} build_single_descriptor: selector not found: {}",
+                                filter.context_id, attribute_path
+                            );
+                            match &selector_item.default {
+                                None => return None, // skipping the entire descriptor
+                                Some(default_value) => default_value.clone(),
+                            }
+                        }
+                        // TODO(eastizle): not all fields are strings
+                        // https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/advanced/attributes
+                        Some(attribute_bytes) => Attribute::parse(attribute_bytes)
+                            .inspect_err(|e| debug!("#{} build_single_descriptor: failed to parse selector value: {}, error: {}",
+                                    filter.context_id, attribute_path, e))
+                            .ok()?,
+                    };
                     let mut descriptor_entry = RateLimitDescriptor_Entry::new();
                     descriptor_entry.set_key(descriptor_key);
                     descriptor_entry.set_value(value);