Return whether file has been deleted succesfully when delete is used.

[QazCetelic]

This avoids needing to stat the object afterwards beforehand

delete currently returns Result<()>. This could be changed to bool or Option<bool> if some backends don't provide that information.

[Xuanwo]

We don't need that. Because what we ensure is "if delete returns Ok(()), this file must be non-exist". Here are two conditions: the file has been deleted or the file didn't exist for the first place.

In either cases, you don't need to check object metadata after calling delete().

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If you do find that a file is still exist after delete() returns Ok(()). It's likely to be a bug, please report which service you are using.

[QazCetelic]

Thanks for taking the time to answer. Apologies for the delayed response. I was quite busy.

I've been experimenting with OpenDAL by trying to implement a distributed FIFO message queue. My specific use case is that I want to "move" a file once (this often means copying and deleting a file) and want to detect if another process connected to the same storage backend does so concurrently to avoid duplicating files.

sequenceDiagram
    participant ProcessA
    participant ProcessB
    participant StorageBackend

    Note over StorageBackend: Initial state: File exists at /source/file.txt
    
    ProcessA->>StorageBackend: Check if /source/file.txt exists
    ProcessB->>StorageBackend: Check if /source/file.txt exists
    
    StorageBackend-->>ProcessA: File exists
    StorageBackend-->>ProcessB: File exists
    
    ProcessA->>StorageBackend: COPY /source/file.txt to /destA/file.txt
    ProcessB->>StorageBackend: COPY /source/file.txt to /destB/file.txt
    
    StorageBackend-->>ProcessA: COPY successful
    StorageBackend-->>ProcessB: COPY successful
    
    ProcessA->>StorageBackend: DELETE /source/file.txt
    ProcessB->>StorageBackend: DELETE /source/file.txt
    
    StorageBackend-->>ProcessA: DELETE successful
    StorageBackend-->>ProcessB: DELETE successful
    
    Note over ProcessA,ProcessB: Both processes think they "moved" the file
    Note over StorageBackend: File duplicated at /destA/file.txt AND /destB/file.txt

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However, considering S3 apparently always returns the same response when deleting a file, I'll just implement it using the following procedure:

1. Copy file
2. Wait
3. Stat file to see if it exists
   4a. Delete source file
   4b. Delete new file