java.nio.file.FileSystemNotFoundException on FileSystems.getFileSystem

[stefanofornari]

Bug Description

FileSystems.getFileSystem() throws a FileSystemNotFoundException if the file system has not been created before. This could be acceptable if FileSystems.newFileSystem(URI.create(file), new HashMap<>()) would be smart enough to return an existing FS if already created. Instead newFileSystem() throws a FileSystemAlreadyExistsException if called twice.
Alternatively, getFileSystem could return null, so to allow the pattern below (which now does not work):

FileSystem fs = FileSystems.getFileSystem(URI.create(file));
if (fs == null) {
        fs = FileSystems.newFileSystem(URI.create(file), new HashMap<>());
}

Steps To Reproduce

see description

Expected Behavior

• getFileSystem() returns a new FileSystem if not already created?
• getFileSystem() returns null?
• newFileSystem() returns an existing FS if already created?

Environment

• s3fs-nio version: 1.0.0 (also 1.0.1)

[steve-todorov]

Hey @stefanofornari ,

Thanks for reporting this.

There is a bug left in some of the legacy code we've inherited. It was preventing an internal property's state to be visible from other threads and this messed up the getFileSystem method logic. I believe this should be fixed with #717. Could you try it out and let me know?

Your suggestion for returning null is not possible because it contradicts the java.nio.file.FileSystems#getFileSystem method's documentation:

Furthermore, the FileSystems method is a final one so we can't really change anything.
You can wrap your code in a try/catch that catches java.nio.file.ProviderNotFoundException instead of doing a null check and you'll achieve the same result :)

[stefanofornari]

Hi Steve, thanks, I will give it a try and let you know.

Furthermore, the FileSystems method is a final one so we can't really change anything.

I did not mean to extend FileSystems, but to fix the implementation in s3fs-nio provider.

[steve-todorov]

My bad then. Anyway let me know if this fixes it :)