feat: Add write_can_empty in Capability and related tests

core/src/raw/adapters/kv/backend.rs

@@ -84,6 +84,7 @@ impl<S: Adapter> Accessor for Backend<S> {
         }
 
         if cap.write {
+            cap.write_can_empty = true;
             cap.create_dir = true;
             cap.delete = true;
         }

core/src/raw/adapters/typed_kv/backend.rs

@@ -84,6 +84,7 @@ impl<S: Adapter> Accessor for Backend<S> {
 
         if kv_cap.set {
             cap.write = true;
+            cap.write_can_empty = true;
             cap.create_dir = true;
         }
 

core/src/raw/oio/write/multipart_upload_write.rs

@@ -258,7 +258,13 @@ where
                                     (w, res)
                                 }));
                             }
-                            None => return Poll::Ready(Ok(())),
+                            None => {
+                                // Call write_once if there is no data in cache and no upload_id.
+                                self.state = State::Close(Box::pin(async move {
+                                    let res = w.write_once(0, AsyncBody::Empty).await;
+                                    (w, res)
+                                }));
+                            }
                         },
                     }
                 }

core/src/raw/oio/write/range_write.rs

@@ -223,7 +223,13 @@ impl<W: RangeWrite> oio::Write for RangeWriter<W> {
                                     (w, res)
                                 }));
                             }
-                            None => return Poll::Ready(Ok(())),
+                            None => {
+                                // Call write_once if there is no data in buffer and no location.
+                                self.state = State::Complete(Box::pin(async move {
+                                    let res = w.write_once(0, AsyncBody::Empty).await;
+                                    (w, res)
+                                }));
+                            }
                         },
                     }
                 }

core/src/services/azblob/backend.rs

@@ -529,6 +529,7 @@ impl Accessor for AzblobBackend {
                 read_with_override_content_disposition: true,
 
                 write: true,
+                write_can_empty: true,
                 write_can_append: true,
                 write_with_cache_control: true,
                 write_with_content_type: true,

core/src/services/cos/backend.rs

@@ -265,6 +265,7 @@ impl Accessor for CosBackend {
                 read_with_if_none_match: true,
 
                 write: true,
+                write_can_empty: true,
                 write_can_append: true,
                 write_can_multi: true,
                 write_with_content_type: true,

core/src/services/fs/backend.rs

@@ -267,6 +267,7 @@ impl Accessor for FsBackend {
                 read_with_range: true,
 
                 write: true,
+                write_can_empty: true,
                 write_can_append: true,
                 write_can_multi: true,
                 create_dir: true,

core/src/services/gcs/backend.rs

@@ -334,6 +334,7 @@ impl Accessor for GcsBackend {
                 read_with_if_none_match: true,
 
                 write: true,
+                write_can_empty: true,
                 write_can_multi: true,
                 write_with_content_type: true,
                 // The buffer size should be a multiple of 256 KiB (256 x 1024 bytes), unless it's the last chunk that completes the upload.

core/src/services/obs/backend.rs

@@ -272,6 +272,7 @@ impl Accessor for ObsBackend {
                 read_with_if_none_match: true,
 
                 write: true,
+                write_can_empty: true,
                 write_can_append: true,
                 write_can_multi: true,
                 write_with_content_type: true,

core/src/services/oss/backend.rs

@@ -398,6 +398,7 @@ impl Accessor for OssBackend {
                 read_with_if_none_match: true,
 
                 write: true,
+                write_can_empty: true,
                 write_can_append: true,
                 write_can_multi: true,
                 write_with_cache_control: true,

core/src/services/s3/backend.rs

@@ -913,6 +913,7 @@ impl Accessor for S3Backend {
                 read_with_override_content_type: true,
 
                 write: true,
+                write_can_empty: true,
                 write_can_multi: true,
                 write_with_cache_control: true,
                 write_with_content_type: true,

core/src/services/webdav/backend.rs

@@ -238,6 +238,7 @@ impl Accessor for WebdavBackend {
                 read_with_range: true,
 
                 write: true,
+                write_can_empty: true,
 
                 create_dir: true,
                 delete: true,

core/src/types/capability.rs

@@ -76,6 +76,8 @@ pub struct Capability {
     pub write: bool,
     /// If operator supports write can be called in multi times.
     pub write_can_multi: bool,
+    /// If operator supports write with empty content.
+    pub write_can_empty: bool,
     /// If operator supports write by append.
     pub write_can_append: bool,
     /// If operator supports write with content type.

core/tests/behavior/write.rs

@@ -48,6 +48,7 @@ pub fn behavior_write_tests(op: &Operator) -> Vec<Trial> {
         test_create_dir,
         test_create_dir_existing,
         test_write_only,
+        test_write_with_empty_content,
         test_write_with_dir_path,
         test_write_with_special_chars,
         test_write_with_cache_control,
@@ -136,6 +137,23 @@ pub async fn test_write_only(op: Operator) -> Result<()> {
     Ok(())
 }
 
+/// Write a file with empty content.
+pub async fn test_write_with_empty_content(op: Operator) -> Result<()> {
+    if !op.info().full_capability().write_can_empty {
+        return Ok(());
+    }
+
+    let path = uuid::Uuid::new_v4().to_string();
+
+    op.write(&path, vec![]).await?;
+
+    let meta = op.stat(&path).await.expect("stat must succeed");
+    assert_eq!(meta.content_length(), 0);
+
+    op.delete(&path).await.expect("delete must succeed");
+    Ok(())
+}
+
 /// Write file with dir path should return an error
 pub async fn test_write_with_dir_path(op: Operator) -> Result<()> {
     let path = format!("{}/", uuid::Uuid::new_v4());