cli-output: Minor refactor of CliFees

cli-output/src/cli_output.rs

@@ -1457,17 +1457,17 @@ impl fmt::Display for CliSupply {
 
 #[derive(Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
-pub struct CliFees {
+pub struct CliFeesInner {
     pub slot: Slot,
     pub blockhash: String,
     pub lamports_per_signature: u64,
-    pub last_valid_slot: Slot,
+    pub last_valid_slot: Option<Slot>,
 }
 
-impl QuietDisplay for CliFees {}
-impl VerboseDisplay for CliFees {}
+impl QuietDisplay for CliFeesInner {}
+impl VerboseDisplay for CliFeesInner {}
 
-impl fmt::Display for CliFees {
+impl fmt::Display for CliFeesInner {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         writeln_name_value(f, "Blockhash:", &self.blockhash)?;
         writeln_name_value(
@@ -1480,6 +1480,46 @@ impl fmt::Display for CliFees {
     }
 }
 
+#[derive(Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct CliFees {
+    #[serde(flatten, skip_serializing_if = "Option::is_none")]
+    pub inner: Option<CliFeesInner>,
+}
+
+impl QuietDisplay for CliFees {}
+impl VerboseDisplay for CliFees {}
+
+impl fmt::Display for CliFees {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self.inner.as_ref() {
+            Some(inner) => write!(f, "{}", inner),
+            None => write!(f, "Fees unavailable"),
+        }
+    }
+}
+
+impl CliFees {
+    pub fn some(
+        slot: Slot,
+        blockhash: Hash,
+        lamports_per_signature: u64,
+        last_valid_slot: Option<Slot>,
+    ) -> Self {
+        Self {
+            inner: Some(CliFeesInner {
+                slot,
+                blockhash: blockhash.to_string(),
+                lamports_per_signature,
+                last_valid_slot,
+            }),
+        }
+    }
+    pub fn none() -> Self {
+        Self { inner: None }
+    }
+}
+
 #[derive(Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub struct CliTokenAccount {

cli/src/cluster_query.rs

@@ -823,12 +823,12 @@ pub fn process_cluster_version(rpc_client: &RpcClient, config: &CliConfig) -> Pr
 pub fn process_fees(rpc_client: &RpcClient, config: &CliConfig) -> ProcessResult {
     let result = rpc_client.get_recent_blockhash_with_commitment(config.commitment)?;
     let (recent_blockhash, fee_calculator, last_valid_slot) = result.value;
-    let fees = CliFees {
-        slot: result.context.slot,
-        blockhash: recent_blockhash.to_string(),
-        lamports_per_signature: fee_calculator.lamports_per_signature,
+    let fees = CliFees::some(
+        result.context.slot,
+        recent_blockhash,
+        fee_calculator.lamports_per_signature,
         last_valid_slot,
-    };
+    );
     Ok(config.output_format.formatted_string(&fees))
 }