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Re: packaging a golang package

From: Timmy Douglas
Subject: Re: packaging a golang package
Date: Sat, 09 Jan 2021 16:32:45 -0800 
"Leo Famulari" <leo@famulari.name> writes:

> On Fri, Jan 8, 2021, at 02:01, Timmy Douglas wrote:
>> 
>> I recently installed guix for the first time and I wanted to try to
>> package my first program. The one I decided to try is written in go and
>> uses go.mod (https://github.com/coredns/coredns/blob/master/go.mod) for
>> modules. Running `go build` would normally download those if they don't
>> exist.
>> 
>> I took a look at a couple of other packages, and it looks like the right
>> way to do it would be to package the individual modules as seen in
>> guix/gnu/packages/golang.scm. Has anyone tried automating this sort of
>> thing? There are almost 40 dependencies...
>
> Thanks for working on this!
>
> It's true, Go programs usually have a dependency graph that is
> uncomfortably large — although not impossibly large like Rust.
>
> There is a work-in-progress implementation of a Go package importer
> that I believe should make it easier:
>
> https://issues.guix.gnu.org/issue/44178
>
> You could try it out and, if it works for you, send those patches, and
> give feedback on the importer as well :)

Thanks for the pointer!

I tried both Katherine's patch (with dftxbs3e's mini fix for
recursive-import) and Helio's patch (with a git remote add/cherry-pick)
and had trouble with both of them. I spent a little more time with
Katherine's patch so I'll go into that more below.

Part of the issue is that I haven't used Scheme in like 15 years (and
when I did, it wasn't for anything non-trivial). But I'm also really
struggling to debug what's going on:

I run `make && ./pre-inst-env guix import go -r github.com/coredns/coredns`:

Starting download of /tmp/guix-file.pZqXNO
>From https://proxy.golang.org/k8s.io/klog/@v/v1.0.0.mod...
 v1.0.0.mod  68B                       88KiB/s 00:00 [##################] 100.0%
metadata#f
Backtrace:
In ice-9/boot-9.scm:
  1736:10 13 (with-exception-handler _ _ #:unwind? _ # _)
In unknown file:
          12 (apply-smob/0 #<thunk 7f98846a3740>)
In ice-9/boot-9.scm:
    718:2 11 (call-with-prompt _ _ #<procedure default-prompt-handle?>)
In ice-9/eval.scm:
    619:8 10 (_ #(#(#<directory (guile-user) 7f98842e0f00>)))
In guix/ui.scm:
  2154:12  9 (run-guix-command _ . _)
In guix/scripts/import.scm:
   120:11  8 (guix-import . _)
In ice-9/eval.scm:
    159:9  7 (_ _)
In guix/import/utils.scm:
   468:27  6 (recursive-import _ #:repo->guix-package _ #:guix-name _ ?)
In srfi/srfi-1.scm:
   586:17  5 (map1 (("k8s.io/klog" #f) ("k8s.io/client-go" #f) (?) ?))
In guix/import/utils.scm:
   457:33  4 (lookup-node "k8s.io/klog" #f)
In guix/utils.scm:
    703:8  3 (call-with-temporary-output-file #<procedure 7f9871b8c7?>)
In ice-9/eval.scm:
   293:34  2 (_ #(#(#(#(#(#(#(#(#<directory ?> ?) ?) ?) ?) ?) ?) ?) ?))
    155:9  1 (_ #(#(#<directory (guix import go) 7f9882267f00>) #f))
In unknown file:
           0 (list-ref #f 1)

ERROR: In procedure list-ref:
In procedure list-ref: Wrong type argument in position 1: #f


I understand that (list-ref #f 1) won't work, but I can't figure out
where that code is based on the information in the backtrace. Seems like
the variables/symbols/filenames are missing everywhere where it counts.

I loaded the code up with #'display and found that I needed to add
another git scs/vcs entry for k8s.io, and that the
fetch-module-meta-data method tries to use regexes to parse html:

root-module-path= k8s.io/klog
line=
line=            <html><head>
line=                  <meta name="go-import"
line=                        content="k8s.io/klog
line=                                 git https://github.com/kubernetes/klog";>
line=                  <meta name="go-source"
line=                        content="k8s.io/klog
line=                                 https://github.com/kubernetes/klog
line=                                 
https://github.com/kubernetes/klog/tree/master{/dir}
line=                                 
https://github.com/kubernetes/klog/blob/master{/dir}/{file}#L{line}";>
line=            </head></html>
line=

(define (fetch-module-meta-data module-path)
  "Fetches module meta-data from a module's landing page. This is necessary
because goproxy servers don't currently provide all the information needed to
build a package."
  (let* ((port (http-fetch (string->uri (format #f "https://~a?go-get=1"; 
module-path))))
         (module-metadata #f)
         (meta-tag-prefix "<meta name=\"go-import\" content=\"")
         (meta-tag-prefix-length (string-length meta-tag-prefix)))
    (do ((line (read-line port) (read-line port)))
        ((or (eof-object? line)
             module-metadata))
      (let ((meta-tag-index (string-contains line meta-tag-prefix)))
        (display "line=")
        (display line)
        (newline)
        (when meta-tag-index
          (let* ((start (+ meta-tag-index meta-tag-prefix-length))
                 (end (string-index line #\" start)))
            (set! module-metadata
              (string-split (substring/shared line start end) #\space))))))
    (close-port port)
    module-metadata))


I don't think the regex would match due to content="" being put on
another line--so #f is returned and causes a type exception later. I'm
a little more used to statically typed languages so tracing it back to
there took longer than I would have liked.

Maybe I need to find a video tutorial on writing Scheme for Guix or
similiar? I felt like I was doing the wrong thing with
printf/make/pre-inst-env guix. I tried starting geiser in emacs, but
didn't really know what I should evaluate. It also added an unbearable
lag to typing in the scheme buffer and didn't provide auto-completion or
symbol lookup, so I didn't go too far with it...

Would be interested if Katherine or Helio have any more updates.
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