fix build, skip serialize None

src/core/index.rs

@@ -526,7 +526,6 @@ mod tests {
     use crate::schema::Field;
     use crate::schema::{Schema, INDEXED, TEXT};
     use crate::IndexReader;
-    use crate::IndexSettings;
     use crate::ReloadPolicy;
     use crate::{Directory, Index};
 
@@ -548,12 +547,7 @@ mod tests {
     fn test_index_exists() {
         let directory = RamDirectory::create();
         assert!(!Index::exists(&directory).unwrap());
-        assert!(Index::create(
-            directory.clone(),
-            throw_away_schema(),
-            IndexSettings::default()
-        )
-        .is_ok());
+        assert!(Index::create(directory.clone(), throw_away_schema(), None).is_ok());
         assert!(Index::exists(&directory).unwrap());
     }
 

src/core/index_meta.rs

@@ -207,6 +207,7 @@ pub struct IndexSettings {}
 #[derive(Clone, Serialize)]
 pub struct IndexMeta {
     /// `IndexSettings` to configure index options.
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub index_settings: Option<IndexSettings>,
     /// List of `SegmentMeta` informations associated to each finalized segment of the index.
     pub segments: Vec<SegmentMeta>,
@@ -308,7 +309,7 @@ mod tests {
         let json = serde_json::ser::to_string(&index_metas).expect("serialization failed");
         assert_eq!(
             json,
-            r#"{"index_settings":{},"segments":[],"schema":[{"name":"text","type":"text","options":{"indexing":{"record":"position","tokenizer":"default"},"stored":false}}],"opstamp":0}"#
+            r#"{"segments":[],"schema":[{"name":"text","type":"text","options":{"indexing":{"record":"position","tokenizer":"default"},"stored":false}}],"opstamp":0}"#
         );
     }
 }

src/directory/mmap_directory.rs

@@ -487,7 +487,6 @@ mod tests {
     use super::*;
     use crate::schema::{Schema, SchemaBuilder, TEXT};
     use crate::Index;
-    use crate::IndexSettings;
     use crate::ReloadPolicy;
     use crate::{common::HasLen, indexer::LogMergePolicy};
 
@@ -586,8 +585,7 @@ mod tests {
         let schema = schema_builder.build();
 
         {
-            let index =
-                Index::create(mmap_directory.clone(), schema, IndexSettings::default()).unwrap();
+            let index = Index::create(mmap_directory.clone(), schema, None).unwrap();
 
             let mut index_writer = index.writer_for_tests().unwrap();
             let mut log_merge_policy = LogMergePolicy::default();