Simplify error handling for Query::get_best_header()

src/query.rs

@@ -267,9 +267,10 @@ impl Query {
         result
     }
 
-    pub fn get_best_header(&self) -> Option<HeaderEntry> {
+    pub fn get_best_header(&self) -> Result<HeaderEntry> {
         let header_list = self.app.index().headers_list();
-        Some(header_list.headers().last()?.clone())
+        let last_header = header_list.headers().last();
+        Ok(last_header.chain_err(|| "no headers indexed")?.clone())
     }
 
     pub fn get_merkle_proof(

src/rpc.rs

@@ -58,9 +58,7 @@ impl Connection {
     }
 
     fn blockchain_headers_subscribe(&mut self) -> Result<Value> {
-        let entry = self.query
-            .get_best_header()
-            .chain_err(|| "no headers found")?;
+        let entry = self.query.get_best_header()?;
         self.last_header_entry = Some(entry.clone());
         Ok(jsonify_header(entry.header(), entry.height()))
     }
@@ -210,9 +208,7 @@ impl Connection {
     fn update_subscriptions(&mut self) -> Result<Vec<Value>> {
         let mut result = vec![];
         if let Some(ref mut last_entry) = self.last_header_entry {
-            let entry = self.query
-                .get_best_header()
-                .chain_err(|| "no headers found")?;
+            let entry = self.query.get_best_header()?;
             if *last_entry != entry {
                 *last_entry = entry;
                 let header = jsonify_header(last_entry.header(), last_entry.height());