Re: [Libguestfs] Publishing the libnbd go module

25 Oct 2021

      On Mon, Oct 25, 2021 at 5:01 PM Richard W.M. Jones <rjones@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/l...
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.
So the import path should be:

    gitlab.com/libnbd/golang/src/libguestfs.org/libnbd

Since gitlab (or github) already supports go tools.

...
...
...
$ 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 )?
Yes, this is how I understand the docs. I did not try it yet.

Nir