Try not to panic with a weird composite index

introspection-engine/connectors/mongodb-introspection-connector/src/sampler/statistics/indices.rs

@@ -216,13 +216,10 @@ fn add_missing_types_from_index(
                 .iter()
                 .find(|f| f.database_name.as_deref() == Some(field_name) || f.name == field_name);
 
-            next_type = match cf {
-                Some(_) if i + 1 == path_length => None,
-                Some(cf) => {
-                    let type_name = cf.r#type.as_composite_type().unwrap();
-                    Some(type_name.to_string())
-                }
-                None => {
+            next_type = match (cf, cf.and_then(|cf| cf.r#type.as_composite_type())) {
+                (Some(_), _) if i + 1 == path_length => None,
+                (Some(_), Some(type_name)) => Some(type_name.to_string()),
+                (None, _) | (_, None) => {
                     let docs = String::from("Field referred in an index, but found no data to define the type.");
 
                     let (field_name, database_name) = match super::sanitize_string(field_name) {

introspection-engine/connectors/mongodb-introspection-connector/tests/index/mod.rs

@@ -1985,3 +1985,46 @@ fn composite_type_index_without_corresponding_data_should_not_crash() {
 
     expected.assert_eq(res.datamodel());
 }
+
+#[test]
+fn composite_type_index_with_non_composite_fields_in_the_middle_should_not_crash() {
+    let res = introspect(|db| async move {
+        db.create_collection("A", None).await?;
+        let collection = db.collection::<mongodb::bson::Document>("A");
+
+        let model = IndexModel::builder().keys(doc! { "a.b.c": 1 }).build();
+        collection.create_index(model, None).await?;
+
+        let docs = vec![doc! { "a": { "b": 1, "d": { "c": 1 } } }];
+        collection.insert_many(docs, None).await.unwrap();
+
+        Ok(())
+    });
+
+    let expected = expect![[r#"
+        type AA {
+          b Int
+          d AaD
+          /// Field referred in an index, but found no data to define the type.
+          b AaB?
+        }
+
+        type AaB {
+          /// Field referred in an index, but found no data to define the type.
+          c Json?
+        }
+
+        type AaD {
+          c Int
+        }
+
+        model A {
+          id String @id @default(auto()) @map("_id") @db.ObjectId
+          a  AA
+
+          @@index([a.b.c], map: "a.b.c_1")
+        }
+    "#]];
+
+    expected.assert_eq(res.datamodel());
+}