[Adding Matthew]

On Mon, Oct 25, 2021 at 04:45:03PM +0300, Nir Soffer wrote:
> I'm playing with libnbd go module, planning to use it in a new command[1]
>
> The biggest obstacle for me is that the module is not published in a way that
> Go developers expect.
>
> The module is listed in:
> https://pkg.go.dev/github.com/libguestfs/libnbd/golang
>
> But the module actually lives in:
> https://github.com/libguestfs/libnbd/tree/master/golang/src/libguestfs.org/libnbd
>
> So the pkg.go.dev page is broken, .e.g no there is no documation or license, and
> the suggested import is wrong.
>
> The module name is "libguestfs.org/libnbd". But if you try to use it,
> for example
> in the (improved) example from libnbd-golang.pod:
>
> $ cat test.go
> package main
>
> import "fmt"
> import "libguestfs.org/libnbd"
>
> func main() {
>     h, err := libnbd.Create()
>     if err != nil {
>         panic(err)
>     }
>     defer h.Close()
>     uri := "nbd://localhost"
>     err = h.ConnectUri(uri)
>     if err != nil {
>         panic(err)
>     }
>     size, err := h.GetSize()
>     if err != nil {
>         panic(err)
>     }
>     fmt.Printf("size of %s = %d\n", uri, size)
> }
>
> $ go mod init example/test
> go: creating new go.mod: module example/test
> go: to add module requirements and sums:
>         go mod tidy
>
> $ go mod tidy
> go: finding module for package libguestfs.org/libnbd
> example/test imports
>         libguestfs.org/libnbd: cannot find module providing package
> libguestfs.org/libnbd: unrecognized import path
> "libguestfs.org/libnbd": reading
> https://libguestfs.org/libnbd?go-get=1: 404 Not Found

That website is entirely static so if it involves fetching stuff from
there it's probably not going to work.

> If we use libguestfs.org, https://libguestfs.org/libnbd?go-get=1
> should return the expected
> metadata instead of 404.
>
> But even if "libguestfs.org/libnbd" would work, we cannot use the
> module from the source
> since the source is missing the generated files (wrappers.go, binding.go, ...).

I believe that Matthew hit this problem too ...

> It looks like the only ways to use the module are:
>
> - Vendor the go code from the tarball.
>
> I did not try this since I don't want to copy libnbd into source into
> my project.
>
> - Clone and build libnbd locally, and replace libguestfs.org with the
> path to your local source
>
> $ go mod edit -replace
> libguestfs.org/libnbd=../../src/libnbd/golang/src/libguestfs.org/libnbd
> $ go mod tidy
> go: found libguestfs.org/libnbd in libguestfs.org/libnbd
> v0.0.0-00010101000000-000000000000
>
> $ cat go.mod
> module example/test
>
> go 1.16
>
> replace libguestfs.org/libnbd =>
> ../../src/libnbd/golang/src/libguestfs.org/libnbd
>
> require libguestfs.org/libnbd v0.0.0-00010101000000-000000000000
>
>
> But the version is wrong - it should be v1.10.0.
> I think the issue is missing tag:
> https://golang.org/ref/mod#vcs-version
>
>     If a module is defined in a subdirectory within the repository,
> that is, the module subdirectory
>     portion of the module path is not empty, then each tag name must
> be prefixed with the module
>     subdirectory, followed by a slash. For example, the module
> golang.org/x/tools/gopls is defined
>     in the gopls subdirectory of the repository with root path
> golang.org/x/tools. The version v0.4.0
>     of that module must have the tag named gopls/v0.4.0 in that repository.
>
> So the linbd project needs a tag like:
> golang/src/libguestfs.org/libnbd/v1.10.0

I'm not sure I understand what this all means.  Is that the literal
name of the git tag (ie.
git tag golang/src/libguestfs.org/libnbd/v1.10.0 )?

> Removing the "src/libguestfs.org" directories will clean things up:
> golang/libnbd/v1.10.0
>
> I hope we can solve this issue. Making the go binding easy to use for
> developers is
> important for making libnbd more popular in the Go community.
>
> [1] https://gerrit.ovirt.org/c/ovirt-imageio/+/117277

Rich.

--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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