Impl OptionalFromRequest on MultipartFile and change behaviour on MultipartFiles to contain 0 files

src/axum/extractor.rs

@@ -1,10 +1,11 @@
-use axum::{
-    extract::{
-        FromRequest, Multipart, Request,
-        multipart::{Field, MultipartError, MultipartRejection},
-    },
-    response::IntoResponse,
-};
+use axum::extract::FromRequest;
+use axum::extract::Multipart;
+use axum::extract::OptionalFromRequest;
+use axum::extract::Request;
+use axum::extract::multipart::Field;
+use axum::extract::multipart::MultipartError;
+use axum::extract::multipart::MultipartRejection;
+use axum::response::IntoResponse;
 use mime::Mime;
 use std::str::FromStr;
 use thiserror::Error;
@@ -140,6 +141,40 @@ where
     }
 }
 
+impl<S> OptionalFromRequest<S> for MultipartFile
+where
+    S: Send + Sync,
+{
+    type Rejection = MultipartFileRejection;
+
+    /// Extracts a single file from a multipart request.
+    /// Expects exactly one file. A file must have a name, bytes and optionally a content type.
+    /// This extractor consumes the request and must ble placed last in the handler.
+    /// # Example
+    /// ```
+    /// use std::io::Read;
+    /// use axum::response::Html;
+    /// use lib::axum::extractor::{MultipartFile, MultipartFiles};
+    ///
+    /// async fn upload_file(opt_file: Option<MultipartFile>) -> Html<String> {
+    ///     Html(opt_file
+    ///         .map(|MultipartFile(file)| String::from_utf8(file.bytes).unwrap())
+    ///         .unwrap_or_else(|| String::from("<p>Not Found</p>"))
+    ///     )
+    /// }
+    /// ```
+    async fn from_request(req: Request, state: &S) -> Result<Option<Self>, Self::Rejection> {
+        let multipart = Multipart::from_request(req, state).await?;
+        let files = get_files(multipart).await?;
+        if files.len() > 1 {
+            Err(MultipartFileRejection::SeveralFiles)
+        } else {
+            let file = files.first().ok_or(MultipartFileRejection::NoFiles)?;
+            Ok(Some(MultipartFile(file.clone())))
+        }
+    }
+}
+
 impl<S> FromRequest<S> for MultipartFiles
 where
     S: Send + Sync,
@@ -147,7 +182,7 @@ where
     type Rejection = MultipartFileRejection;
 
     /// Extracts multiple files from a multipart request.
-    /// Expects at least one file. A file must have a name, bytes and optionally a content type.
+    /// Can contain 0 files. A file must have a name, bytes and optionally a content type.
     /// This extractor consumes the request and must ble placed last in the handler.
     /// # Example
     /// ```
@@ -167,11 +202,7 @@ where
     async fn from_request(req: Request, state: &S) -> Result<Self, Self::Rejection> {
         let multipart = Multipart::from_request(req, state).await?;
         let files = get_files(multipart).await?;
-        if files.is_empty() {
-            Err(MultipartFileRejection::NoFiles)
-        } else {
-            Ok(MultipartFiles(files))
-        }
+        Ok(MultipartFiles(files))
     }
 }