Add FileIO.writeFile

[t-ae]

Adds writeFile method to request's FileIO helper (#2418).

// Writes "hello" to /path/to/file.txt
// Returns a future indicating when the write has completed. 
req.fileio.writeFile(.init(string: "hello"), at: "/path/to/file.txt")

[Joannis]

Thanks for the PR, this is a useful addition! I just wonder what should happen to existing files. Would they append to or overwrite the existing file?

[t-ae]

This method overwrites target file.
For appending, we have to pass O_APPEND flag to NIOFileHandle.

How about to add FileIO.write(fileHandle: NIOFileHandle, buffer: ByteBuffer)?
User can create NIOFileHandle with O_APPEND flag and pass it.
The merit of this method is that user can control when to close fileHandle.
It would be useful especially when appending to single file many times.

[tanner0101]

+1 to adding this. My only concern here is naming.

The other methods on FileIO are named:

• collectFile(at:)
• readFile(at:)
• streamFile(at:)

This newly added method write(to:buffer:) doesn't really fit.

Given that the method creates a new file, what would you think about:

writeFile(_ data: ByteBuffer, at path: String) -> ELFuture<Void>

[t-ae]

@tanner0101
Changed the name as you suggested.

What do you think about appending?
#2418 (comment)
FileIO is just a utility class and users can append files by using NonBlockingFileIO directly.
So I think FileIO doesn't have to have appending method.

[tanner0101]

@t-ae we can always add an append api in the future, I think this is good for now :)

Would you mind including a code example in the PR body? These will auto gen release notes, more info here: https://github.com/vapor/vapor/blob/master/.github/contributing.md#releases

[tanner0101]

Thanks!

[tanner0101]

These changes are now available in 4.24.0