Add async alignment reader

[mbhall88]

See #286 for more details.

Creating this as a draft so if I am too slow and you want to work on this sooner you can use where I got to (if you want).

Checklist

• async Reader
  • Builder
  • Documentation examples
  • examples/ entry

[mbhall88]

I think the async Reader is complete. I haven't added doc examples yet as these will be easier to do once I have implemented the Builder for the Reader.

I'll move on to the Builder after you're happy with everything up to this point @zaeleus. Also, I figured doing all of this in one PR, with reviews at each stage on the checklist, would be best. Though I guess we could do separate PRs for the Reader and Writer. Up to you.

[zaeleus]

so if I am too slow and you want to work on this sooner you can use where I got to (if you want).

No rush and no worries.

I haven't added doc examples yet as these will be easier to do once I have implemented the Builder for the Reader.

Examples are not dependent on the builder. The enum variants are public, and one can be selected for the test, e.g., this example written before the builder was available:

noodles/noodles-util/src/variant/async/io/reader.rs

Lines 22 to 40 in 21486a1

	/// Reads the VCF header.
	///
	/// # Examples
	///
	/// ```
	/// # #[tokio::main]
	/// # async fn main() -> tokio::io::Result<()> {
	/// use noodles_util::variant::r#async::io::Reader;
	/// use noodles_vcf as vcf;
	///
	/// let data = b"##fileformat=VCFv4.5
	/// #CHROM\tPOS\tID\tREF\tALT\tQUAL\tFILTER\tINFO
	/// ";
	///
	/// let mut reader = Reader::Vcf(vcf::r#async::io::Reader::new(&data[..]));
	/// let _header = reader.read_header().await?;
	/// # Ok(())
	/// # }
	/// ```

Though I guess we could do separate PRs for the Reader and Writer.

I recommend splitting the reader and writer into two PRs. The features are independent, and smaller patches are always easier to reason.

[mbhall88]

I've nearly added the Builder. There is one error when trying to build. The compiler is being ever so patient with me but I seem to be too thick to understand how to resolve the problem

error[E0308]: mismatched types
   --> noodles-util/src/alignment/async/io/reader/builder.rs:168:40
    |
168 |             Format::Bam => Reader::Bam(bam::r#async::io::Reader::new(reader)),
    |                            ----------- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `AsyncReader<Box<dyn AsyncBufRead + Unpin>>`, found `AsyncReader<AsyncReader<Box<dyn AsyncBufRead + Unpin>>>`
    |                            |
    |                            arguments to this enum variant are incorrect
    |
    = note: expected struct `noodles_bam::AsyncReader<Box<dyn tokio::io::AsyncBufRead + Unpin>>`
               found struct `noodles_bam::AsyncReader<noodles_bgzf::AsyncReader<Box<dyn tokio::io::AsyncBufRead + Unpin>>>`
note: tuple variant defined here
   --> noodles-util/src/alignment/async/io/reader.rs:20:5
    |
20  |     Bam(bam::r#async::io::Reader<R>),
    |     ^^^

I can see that this seems to be coming from having an AsyncReader inside another AsyncReader, and I think it might be coming from the bgzf::AsyncReader? Not really sure how to get around this.

No doubt you'll see a simple solution that I am to naive to think of myself (as always) 😅

[zaeleus]

Great work, thanks!