fix: ChainReader fails on find intersect without agency

When the chain sync client does not have agency (i.e. is waiting for the server to callback),
the find intersect point triggered is not allowed and is now skipped.

Author: jpraynaud

mithril-common/src/chain_reader/pallas_chain_reader.rs

@@ -54,9 +54,11 @@ impl PallasChainReader {
         let client = self.get_client().await?;
         let chainsync = client.chainsync();
 
-        chainsync
-            .find_intersect(vec![point.to_owned().into()])
-            .await?;
+        if chainsync.has_agency() {
+            chainsync
+                .find_intersect(vec![point.to_owned().into()])
+                .await?;
+        }
 
         Ok(())
     }
@@ -327,6 +329,19 @@ mod tests {
             let client = chain_reader.get_client().await.unwrap();
             client.chainsync().request_next().await.unwrap();
 
+            // make sure that the chainsync client returns an error when attempting to find intersection without agency
+            client
+                .chainsync()
+                .find_intersect(vec![known_point.clone()])
+                .await
+                .expect_err("chainsync find_intersect without agency should fail");
+
+            // make sure that setting the chain point is harmless when the chainsync client does not have agency
+            chain_reader
+                .set_chain_point(&ChainPoint::from(known_point.clone()))
+                .await
+                .unwrap();
+
             chain_reader.get_next_chain_block().await.unwrap().unwrap()
         });