From 834aed420b9926a78b39455c1274465c7b574a0b Mon Sep 17 00:00:00 2001
From: David Newell <d.newell1@outlook.com>
Date: Thu, 24 Oct 2024 14:50:06 +0100
Subject: [PATCH] chore: skip when exception list is missing (#25784)

---
 rust/cymbal/src/main.rs      |  9 +++++++--
 rust/cymbal/src/resolver.rs  |  2 +-
 rust/cymbal/src/types/mod.rs | 30 ++++++++----------------------
 3 files changed, 16 insertions(+), 25 deletions(-)

diff --git a/rust/cymbal/src/main.rs b/rust/cymbal/src/main.rs
index 079aa5c92a6bf..699b4bbd64310 100644
--- a/rust/cymbal/src/main.rs
+++ b/rust/cymbal/src/main.rs
@@ -99,12 +99,17 @@ async fn main() -> Result<(), Error> {
             }
         };
 
-        if properties.exception_list.is_empty() {
+        let Some(exception_list) = &properties.exception_list else {
+            // Known issue that $exception_list didn't exist on old clients
+            continue;
+        };
+
+        if exception_list.is_empty() {
             metrics::counter!(ERRORS, "cause" => "no_exception_list").increment(1);
             continue;
         }
 
-        let Some(trace) = properties.exception_list[0].stacktrace.as_ref() else {
+        let Some(trace) = exception_list[0].stacktrace.as_ref() else {
             metrics::counter!(ERRORS, "cause" => "no_stack_trace").increment(1);
             continue;
         };
diff --git a/rust/cymbal/src/resolver.rs b/rust/cymbal/src/resolver.rs
index d2016cd06eba3..cd277cb654cc0 100644
--- a/rust/cymbal/src/resolver.rs
+++ b/rust/cymbal/src/resolver.rs
@@ -91,7 +91,7 @@ mod test {
 
         let exception: ClickHouseEvent = serde_json::from_str(EXAMPLE_EXCEPTION).unwrap();
         let props: ErrProps = serde_json::from_str(&exception.properties.unwrap()).unwrap();
-        let mut test_stack: Vec<RawFrame> = props.exception_list[0]
+        let mut test_stack: Vec<RawFrame> = props.exception_list.unwrap()[0]
             .stacktrace
             .as_ref()
             .unwrap()
diff --git a/rust/cymbal/src/types/mod.rs b/rust/cymbal/src/types/mod.rs
index 134a0fcb7420c..3a420e6410601 100644
--- a/rust/cymbal/src/types/mod.rs
+++ b/rust/cymbal/src/types/mod.rs
@@ -44,7 +44,7 @@ pub struct Exception {
 #[derive(Debug, Deserialize, Serialize, Clone)]
 pub struct ErrProps {
     #[serde(rename = "$exception_list")]
-    pub exception_list: Vec<Exception>, // Required from exception producers - we will not process events without this
+    pub exception_list: Option<Vec<Exception>>, // Required from exception producers - we will not process events without this. Optional to support older clients, should eventually be removed
     #[serde(skip_serializing_if = "Option::is_none")]
     #[serde(rename = "$exception_type")]
     pub exception_type: Option<String>, // legacy, overridden by exception_list
@@ -69,21 +69,6 @@ mod test {
 
     use super::ErrProps;
 
-    #[test]
-    fn it_requires_exception_list() {
-        let raw: &'static str = include_str!("../../tests/static/raw_ch_exception.json");
-
-        let raw: ClickHouseEvent = serde_json::from_str(raw).unwrap();
-
-        // errors out because of missing exception_list property, which is required
-        let props: Result<ErrProps, Error> = serde_json::from_str(&raw.properties.unwrap());
-        assert!(props.is_err());
-        assert_eq!(
-            props.unwrap_err().to_string(),
-            "missing field `$exception_list` at line 275 column 5"
-        );
-    }
-
     #[test]
     fn it_deserialises_error_props() {
         let raw: &'static str = include_str!("../../tests/static/raw_ch_exception_list.json");
@@ -91,23 +76,24 @@ mod test {
         let raw: ClickHouseEvent = serde_json::from_str(raw).unwrap();
 
         let props: ErrProps = serde_json::from_str(&raw.properties.unwrap()).unwrap();
+        let exception_list = &props.exception_list.unwrap();
 
-        assert_eq!(props.exception_list.len(), 1);
+        assert_eq!(exception_list.len(), 1);
         assert_eq!(
-            props.exception_list[0].exception_type,
+            exception_list[0].exception_type,
             "UnhandledRejection".to_string()
         );
         assert_eq!(
-            props.exception_list[0].exception_message,
+            exception_list[0].exception_message,
             "Unexpected usage".to_string()
         );
-        let mechanism = props.exception_list[0].mechanism.as_ref().unwrap();
+        let mechanism = exception_list[0].mechanism.as_ref().unwrap();
         assert_eq!(mechanism.handled, Some(false));
         assert_eq!(mechanism.mechanism_type, None);
         assert_eq!(mechanism.source, None);
         assert_eq!(mechanism.synthetic, Some(false));
 
-        let stacktrace = props.exception_list[0].stacktrace.as_ref().unwrap();
+        let stacktrace = exception_list[0].stacktrace.as_ref().unwrap();
         assert_eq!(stacktrace.frames.len(), 2);
         let RawFrame::JavaScript(frame) = &stacktrace.frames[0];
 
@@ -144,7 +130,7 @@ mod test {
 
         let props: Result<ErrProps, Error> = serde_json::from_str(raw);
         assert!(props.is_ok());
-        assert_eq!(props.unwrap().exception_list.len(), 0);
+        assert_eq!(props.unwrap().exception_list.unwrap().len(), 0);
 
         let raw: &'static str = r#"{
             "$exception_list": [{