Support for async_fs

[bitdriftr]

Hello, this PR adds a new disk implementation using async-fs. I want to support async-fs because it does not require a Tokio reactor, which I don't have in my current context.

This PR is gated behind a new feature asyncfs.

Let me know if you are interested in this feature. If so, I can work more on the PR to get it upstreamed.

[Copilot]

Pull Request Overview

Adds an optional async-fs based disk backend (feature flag asyncfs) to provide an async file implementation that does not depend on a Tokio reactor.

• Introduces AsyncFile wrapper and NativeFs implementation using async-fs.
• Adds feature flag and dependency wiring in Cargo.toml.
• Re-exports async-fs filesystem types when enabled.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
fusio/src/impls/disk/mod.rs	Adds asyncfs module and re-exports behind feature flag.
fusio/src/impls/disk/asyncfs/mod.rs	Implements AsyncFile with Read/Write traits using async-fs.
fusio/src/impls/disk/asyncfs/fs.rs	Implements NativeFs (Fs trait) using async-fs for filesystem operations.
fusio/Cargo.toml	Adds asyncfs feature and async-fs dependency.

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[Copilot]

The close method does not set self.file to None after closing, so subsequent operations (which use unwrap/expect) will proceed on a closed handle and the panic messages like "write file after closed" will never trigger, leading instead to I/O errors on a logically closed file. Either remove the Option wrapper (if double-close protection is not required) or replace lines 52-53 with something like if let Some(file) = self.file.take() { file.close().await?; } to make the state transition explicit and future unwraps fail predictably.

Suggested change

	let file = self.file.as_mut().expect("close file after closed");
	File::close(file).await?;
	if let Some(file) = self.file.take() {
	File::close(&file).await?;
	} else {
	panic!("close file after closed");
	}

[Copilot]

The error message says "option.create" but the variable is options; adjust the message to "Path not found and options.create is false" (or reference the actual OpenOptions field name) for clarity.

Suggested change

	"Path not found and option.create is false",
	"Path not found and options.create is false",

[Copilot]

unwrap() here can panic (e.g. race deletion, permission issues); propagate the error instead to avoid unexpected panics: let absolute_path = std::fs::canonicalize(&local_path).map_err(|e| Error::Path(Box::new(e)))?;.

Suggested change

	let absolute_path = std::fs::canonicalize(&local_path).unwrap();
	let absolute_path = std::fs::canonicalize(&local_path)
	.map_err(|e| Error::Path(Box::new(e)))?;

[Copilot]

local_path.exists() performs a blocking filesystem call in an async context; prefer using async_fs::metadata (and handling the error) to avoid a potential blocking operation on the async executor thread. Example: let exists = async_fs::metadata(&local_path).await.is_ok(); then branch on exists.

Suggested change

	if !local_path.exists() {
	if !async_fs::metadata(&local_path).await.is_ok() {

[ethe]

Hi @bitdriftr , I'm absolutely insterested in another backend implementation, I'll take a look once it is ready for review.