fix: return error instead of panicing (#83)

* chore: add failing test

* fix: return an error instead of panicing in duckdb convertor

Author: gadomski

src/duckdb.rs

@@ -195,11 +195,40 @@ impl ToDuckSQL for Expr {
                         {
                             format!("{} {} {}", a[0], op, a[1])
                         } else {
-                            unreachable!()
+                            return Err(Error::InvalidOperator(op.to_string()));
                         }
                     }
                 }
             }
         })
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::ToDuckSQL;
+    use crate::{Error, Expr};
+
+    #[test]
+    fn unreachable_code() {
+        // https://github.com/stac-utils/rustac-py/issues/135
+        let expr: Expr = serde_json::from_value(serde_json::json!({
+            "op": "and",
+            "args": [
+                {
+                    "op": "eq",
+                    "args": [{"property": "forecast:horizon"}, "PT48H"]
+                },
+                {
+                    "op": "gte",
+                    "args": [{"property": "forecast:reference_time"}, "2025-05-15T00:00:00Z"]
+                },
+            ],
+        }))
+        .unwrap();
+        assert!(matches!(
+            expr.to_ducksql().unwrap_err(),
+            Error::InvalidOperator(_)
+        ));
+    }
+}

src/error.rs

@@ -87,6 +87,10 @@ pub enum Error {
     #[error("Operator {0} is not implemented for this type.")]
     OpNotImplemented(&'static str),
 
+    /// Invalid operator
+    #[error("{0} is not a valid operator.")]
+    InvalidOperator(String),
+
     /// Expression not reduced to boolean
     #[error("Could not reduce expression to boolean")]
     NonReduced(),