tests: Check that we handle missing fields

Adds a check that we return "continue" on the htlc_accepted_hook if we
don't understand an onion payload in the lsp client plugin because of
missing fields.

Signed-off-by: Peter Neuroth <[email protected]>

libs/gl-plugin/src/lsp.rs

@@ -62,8 +62,12 @@ pub async fn on_htlc_accepted(plugin: Plugin, v: Value) -> Result<Value, anyhow:
     let onion_amt = match req.onion.forward_msat {
         Some(a) => a,
         None => {
-            // An onion without an `amt_to_forward` is unorthodox and can not
-            // be processed by this plugin. Skip it.
+            // An onion payload without an `amt_to_forward` is unorthodox and
+            // can not be processed by this plugin. Skip it.
+            log::debug!(
+                "lsp-plugin: got an onion payload={} without an amt forward_msat.",
+                req.onion.payload
+            );
             return Ok(serde_json::to_value(HtlcAcceptedResponse {
                 result: "continue".to_string(),
                 ..Default::default()

libs/gl-plugin/src/tlv.rs

@@ -191,6 +191,13 @@ impl<'de> Deserialize<'de> for SerializedTlvStream {
     }
 }
 
+impl std::fmt::Display for SerializedTlvStream {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let s = hex::encode(SerializedTlvStream::to_bytes(self.clone()));
+        write!(f, "{s}")
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;