return empty responses if data is unavailable in db

shared/src/commitment_tree.rs

@@ -0,0 +1,13 @@
+use std::sync::LazyLock;
+
+use namada_sdk::borsh::BorshSerializeExt;
+use namada_sdk::masp_primitives::merkle_tree::CommitmentTree;
+use namada_sdk::masp_primitives::sapling::Node;
+
+/// Return an empty serialized [`CommitmentTree`].
+#[inline]
+pub fn empty() -> Vec<u8> {
+    static EMPTY_TREE: LazyLock<Vec<u8>> =
+        LazyLock::new(|| CommitmentTree::<Node>::empty().serialize_to_vec());
+    EMPTY_TREE.clone()
+}

shared/src/lib.rs

@@ -1,5 +1,6 @@
 pub mod block;
 pub mod block_results;
+pub mod commitment_tree;
 pub mod error;
 pub mod extracted_masp_tx;
 pub mod header;

webserver/src/error/tree.rs

@@ -6,16 +6,13 @@ use crate::response::api::ApiErrorResponse;
 
 #[derive(Error, Debug)]
 pub enum TreeError {
-    #[error("Commitment Tree not found")]
-    NotFound,
     #[error("Database error: {0}")]
     Database(String),
 }
 
 impl IntoResponse for TreeError {
     fn into_response(self) -> Response {
         let status_code = match self {
-            TreeError::NotFound => StatusCode::NOT_FOUND,
             TreeError::Database(_) => StatusCode::INTERNAL_SERVER_ERROR,
         };
 

webserver/src/error/witness_map.rs

@@ -6,16 +6,13 @@ use crate::response::api::ApiErrorResponse;
 
 #[derive(Error, Debug)]
 pub enum WitnessMapError {
-    #[error("WitnessMap not found")]
-    NotFound,
     #[error("Database error: {0}")]
     Database(String),
 }
 
 impl IntoResponse for WitnessMapError {
     fn into_response(self) -> Response {
         let status_code = match self {
-            WitnessMapError::NotFound => StatusCode::NOT_FOUND,
             WitnessMapError::Database(_) => StatusCode::INTERNAL_SERVER_ERROR,
         };
 

webserver/src/handler/tree.rs

@@ -2,6 +2,7 @@ use axum::extract::{Query, State};
 use axum::Json;
 use axum_macros::debug_handler;
 use axum_trace_id::TraceId;
+use shared::commitment_tree::empty as empty_tree;
 use shared::error::InspectWrap;
 
 use crate::dto::tree::TreeQueryParams;
@@ -23,12 +24,11 @@ pub async fn get_commitment_tree(
             TreeError::Database(err.to_string())
         })?;
 
-    if let Some((commitment_tree, block_height)) = maybe_commitment_tree {
-        Ok(Json(TreeResponse {
-            commitment_tree,
-            block_height,
-        }))
-    } else {
-        Err(TreeError::NotFound)
-    }
+    let (commitment_tree, block_height) = maybe_commitment_tree
+        .unwrap_or_else(|| (empty_tree(), query_params.height));
+
+    Ok(Json(TreeResponse {
+        commitment_tree,
+        block_height,
+    }))
 }

webserver/src/handler/witness_map.rs

@@ -24,12 +24,11 @@ pub async fn get_witness_map(
             WitnessMapError::Database(err.to_string())
         })?;
 
-    if let Some((witnesses, block_height)) = witnesses_and_height {
-        Ok(Json(WitnessMapResponse::new(
-            BlockHeight(block_height),
-            witnesses,
-        )))
-    } else {
-        Err(WitnessMapError::NotFound)
-    }
+    let (witnesses, block_height) =
+        witnesses_and_height.unwrap_or((Vec::new(), query_params.height));
+
+    Ok(Json(WitnessMapResponse::new(
+        BlockHeight(block_height),
+        witnesses,
+    )))
 }

webserver/src/repository/witness_map.rs

@@ -1,5 +1,8 @@
 use anyhow::Context;
-use diesel::{ExpressionMethods, QueryDsl, RunQueryDsl, SelectableHelper};
+use diesel::{
+    ExpressionMethods, OptionalExtension, QueryDsl, RunQueryDsl,
+    SelectableHelper,
+};
 use orm::schema::witness;
 use orm::witness::WitnessDb;
 use shared::error::ContextDbInteractError;
@@ -35,17 +38,21 @@ impl WitnessMapRepositoryTrait for WitnessMapRepository {
         )?;
 
         conn.interact(move |conn| {
-            let closest_height = witness::table
+            let Some(closest_height) = witness::table
                 .order(abs(witness::dsl::block_height - block_height).asc())
                 .filter(witness::dsl::block_height.le(block_height))
                 .select(witness::dsl::block_height)
                 .first(conn)
+                .optional()
                 .with_context(|| {
                     format!(
                         "Failed to fetch height from the db closest to the \
                          provided height {block_height}"
                     )
-                })?;
+                })?
+            else {
+                return anyhow::Ok((vec![], block_height));
+            };
 
             let witnesses = witness::table
                 .filter(witness::dsl::block_height.eq(closest_height))