[Libguestfs] Publishing the libnbd go module

[Matthew Arnold]

On Mon, Oct 25, 2021 at 10:01 AM Richard W.M. Jones <rjones at redhat.com>
wrote:
> > 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 ...

(I forgot to reply to all...)

I ended up creating a new repository with the generated files:
    https://github.com/mrnold/go-libnbd

In my case it sort of made sense because I also needed to change it to
use LDFLAGS instead of pkg-config, since Bazel ignores pkg-config.
But I would be happy to get rid of this if there's a better way.

On Mon, Oct 25, 2021 at 10:01 AM Richard W.M. Jones <rjones at redhat.com>
wrote:

> [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
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> libguestfs lets you edit virtual machines.  Supports shell scripting,
> bindings from many languages.  http://libguestfs.org
>
>
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