Add platform expression strategy runtime

crates/fidc-core/src/data.rs

@@ -843,6 +843,19 @@ impl DataSet {
                 symbol: symbol.to_string(),
             })
     }
+
+    pub fn require_factor(
+        &self,
+        date: NaiveDate,
+        symbol: &str,
+    ) -> Result<&DailyFactorSnapshot, DataSetError> {
+        self.factor(date, symbol)
+            .ok_or_else(|| DataSetError::MissingSnapshot {
+                kind: "factor",
+                date,
+                symbol: symbol.to_string(),
+            })
+    }
 }
 
 fn read_instruments(path: &Path) -> Result<Vec<Instrument>, DataSetError> {