fix handling empty data

src/logfile/logline.rs

@@ -247,17 +247,36 @@ pub struct FullLogLine {
     pub user_agent: String,
     pub version: TinyAsciiStr<16>,
     pub exception: Option<FullException>,
-    #[serde(default)]
+    #[serde(default, deserialize_with = "deserialize_data")]
     pub data: HashMap<String, String>,
 }
 
+fn deserialize_data<'de, D: Deserializer<'de>>(
+    deserializer: D,
+) -> Result<HashMap<String, String>, D::Error> {
+    #[derive(Deserialize)]
+    #[serde(untagged)]
+    enum Data {
+        Data(HashMap<String, String>),
+        #[allow(dead_code)]
+        Empty(Vec<()>),
+    }
+    let data = Data::deserialize(deserializer)?;
+    Ok(match data {
+        Data::Data(data) => data,
+        Data::Empty(_) => HashMap::default(),
+    })
+}
+
 impl FullLogLine {
     pub fn has_data(&self) -> bool {
         self.data.keys().any(|key| key.as_str() != "app")
     }
 
     pub fn data(&self) -> impl Iterator<Item = (&str, &str)> {
-        self.data.iter().map(|(key, value)| (key.as_str(), value.as_str()))
+        self.data
+            .iter()
+            .map(|(key, value)| (key.as_str(), value.as_str()))
             .filter(|(key, _)| *key != "app")
     }
 }