Unconditional Url parsing breaks NamedPipeConnector on Windows

[blaenk]

On windows, the DEFAULT_DOCKER_HOST is correctly a named pipe path:

testcontainers-rs/testcontainers/src/core/env/config.rs

Lines 32 to 34 in e354b75

	/// The default `DOCKER_HOST` address that a windows client will try to connect to.
	#[cfg(windows)]
	pub const DEFAULT_DOCKER_HOST: &str = "npipe:////./pipe/docker_engine";

However, as part of computing the docker_host() based on the configuration hierarchy, it is unconditionally parsed into a Url:

testcontainers-rs/testcontainers/src/core/env/config.rs

Line 141 in e354b75

Url::from_str(DEFAULT_DOCKER_HOST).expect("default host is valid URL")

This has the effect of normalizing the Url into the following value (note the removed period from the beginning of .pipe):

npipe:////pipe/docker_engine

When bollard attempts to connect through that named pipe, it removes the npipe:// prefix, expecting to be left with just //.pipe/docker_engine, but due to this artifact, it is instead left with //pipe/docker_engine.

https://github.com/fussybeaver/bollard/blob/865805f87e4066dbf1a283139e1c6148b62ccd80/src/docker.rs#L838-L843

This results in:

called `Result::unwrap()` on an `Err` value: Client(CreateContainer(HyperLegacyError { err: hyper_util::client::legacy::Error(Connect, Os { code: 53, kind: NotFound, message: "The network path was not found." }) }))

I confirmed this is a problem by forking this repo and hardcoding the value passed into the bollard client with the named path "npipe:////./pipe/docker_engine"

testcontainers-rs/testcontainers/src/core/client/bollard_client.rs

Lines 31 to 36 in e354b75

	#[cfg(windows)]
	"npipe" => Docker::connect_with_named_pipe(
	host.as_str(),
	DEFAULT_TIMEOUT.as_secs(),
	API_DEFAULT_VERSION,
	),

I think we can still parse into a Url to check the scheme for example, but we probably shouldn't use the parsed Url itself to pass on to clients. Consider that the bollard and hyper clients just take an &str anyway. If there's an error with the url formatting, it'll come out eventually.

Separately, It might be worthwhile adding a matrix to also run tests against Windows.

[DDtKey]

Thank you for the detailed description!
I’ll try to add windows runners into CI matrix

I think the main issue is normalization, and there is no way (currently?) to disable this behavior for Url.

I would like to have stricter and more explicit type used, but it seems related to servo/rust-url#602

So I’m good with proposed solution