Simplify the code when array_each failed

meilisearch-types/src/document_formats.rs

@@ -4,10 +4,8 @@ use std::fs::File;
 use std::io::{self, Seek, Write};
 use std::marker::PhantomData;
 
-use either::Either;
 use memmap2::MmapOptions;
 use milli::documents::{DocumentsBatchBuilder, Error};
-use milli::Object;
 use serde::de::{SeqAccess, Visitor};
 use serde::{Deserialize, Deserializer};
 use serde_json::error::Category;
@@ -135,37 +133,28 @@ fn read_json_inner(
     let mmap = unsafe { MmapOptions::new().map(file)? };
     let mut deserializer = serde_json::Deserializer::from_slice(&mmap);
 
-    match array_each(&mut deserializer, |obj: Object| builder.append_json_object(&obj)) {
-        // The json data has been successfully deserialised and does not need to be processed again.
-        // the data has been successfully transferred to the "update_file" during the deserialisation process.
-        // count ==0 means an empty array
+    match array_each(&mut deserializer, |obj| builder.append_json_object(&obj)) {
+        // The json data has been deserialized and does not need to be processed again.
+        // The data has been transferred to the writer during the deserialization process.
         Ok(Ok(count)) => {
             if count == 0 {
                 return Ok(count as usize);
             }
         }
         Ok(Err(e)) => return Err(DocumentFormatError::Internal(Box::new(e))),
-        // Prefer deserialization as a json array. Failure to do deserialisation using the traditional method.
-        Err(_e) => {
-            #[derive(Deserialize, Debug)]
-            #[serde(transparent)]
-            struct ArrayOrSingleObject {
-                #[serde(with = "either::serde_untagged")]
-                inner: Either<Vec<Object>, Object>,
-            }
-
-            let content: ArrayOrSingleObject = serde_json::from_reader(file)
+        Err(_) => {
+            // If we cannot deserialize the content as an array of object then
+            // we try to deserialize it as a single JSON object.
+            let object = serde_json::from_reader(file)
                 .map_err(Error::Json)
                 .map_err(|e| (payload_type, e))?;
 
-            for object in content.inner.map_right(|o| vec![o]).into_inner() {
             builder
                 .append_json_object(&object)
                 .map_err(Into::into)
                 .map_err(DocumentFormatError::Internal)?;
         }
     }
-    }
 
     let count = builder.documents_count();
     let _ = builder.into_inner().map_err(Into::into).map_err(DocumentFormatError::Internal)?;
@@ -173,12 +162,12 @@ fn read_json_inner(
     Ok(count as usize)
 }
 
-/**
- * The actual handling of the deserialization process in the serde avoids storing the deserialized object in memory.
- * Reference:
- * https://serde.rs/stream-array.html
- * https://github.com/serde-rs/json/issues/160
- */
+/// The actual handling of the deserialization process in serde
+/// avoids storing the deserialized object in memory.
+///
+/// ## References
+/// <https://serde.rs/stream-array.html>
+/// <https://github.com/serde-rs/json/issues/160>
 fn array_each<'de, D, T, F>(deserializer: D, f: F) -> std::result::Result<io::Result<u64>, D::Error>
 where
     D: Deserializer<'de>,