FsLoader makes blocking function calls in async context

[damooo]

FsLoader makes blocking function calls like std::fs::File::open(), buf_reader.read_to_string() etc. in async block. This will lead to starvation of async runtime, and also probable panics.

json-ld/core/src/loader/fs.rs

Lines 110 to 130 in 27c0a80

	async move {
	match self.filepath(vocabulary, &url) {
	Some(filepath) => {
	let file = File::open(filepath).map_err(Error::IO)?;
	let mut buf_reader = BufReader::new(file);
	let mut contents = String::new();
	buf_reader
	.read_to_string(&mut contents)
	.map_err(Error::IO)?;
	let doc = (*self.parser)(vocabulary, &url, contents.as_str())
	.map_err(Error::Parse)?;
	Ok(RemoteDocument::new(
	Some(url),
	Some("application/ld+json".parse().unwrap()),
	doc,
	))
	}
	None => Err(Error::NoMountPoint),
	}
	}
	.boxed()

Expected behaviour:

Should use non blocking async functions, like those in tokio::fs instead.

[timothee-haudebourg]

This is a good point, but I am not comfortable with forcing an async runtime. I am not up to date with efforts to provide a runtime independent async I/O API.