bug#54097: bug#63631: [PATCH] import: go: Handle subpackage versioning correctly.

[Timo Wilken]

Hi Ludo', (hi everyone,)

On Wed Jun 14, 2023 at 11:09 PM CEST, Ludovic Courtès wrote:
> Timo Wilken <guix@twilken.net> skribis:
> > Here's a patch that fixes the reported issue (bug#54097) for me. I've only
> > tested this on the github.com/googleapis/google-cloud-go/compute package so
> > far, though it seems to work there. Perhaps others have more testcases?
> >
> > I don't know enough about Go tooling to use it, so I've just patched the 
> > Guile
> > logic of the importer. (I don't write Go, I just want to package stuff 
> > written
> > in it.) In terms of performance, at least the repo contents are apparently
> > cached by the first `git-checkout-hash' call, even if it fails, so the 
> > second
> > call doesn't have to redownload them.

I've been testing my patch further this weekend, and I have a couple more
patches in the pipeline; I suppose I ought to clean those up and submit them.

In particular, I've got fixes for the following queued up locally:

1. Finding the `module-path-subdir' needs another case for e.g.
   cloud.google.com/go/*.

2. My patch sometimes generates an unnecessary `go-version->git-ref' call.

3. Go versions need to be parsed from go.mod, since some packages require a
   newer Go compiler than our default. This I've got a patch for, but this Go
   version also ought to propagate up the dependency tree. I haven't found an
   easy way to do that, since the importer seems to generate top-level
   packages first, before descending the dep tree...

4. `fetch-module-meta-data' ought to ignore 4xx HTTP errors to follow the
   spec; gonum.org/v1/gonum specifically depends on this behaviour.

I've been trying to recursively import github.com/matrix-org/dendrite, which
has a particularly large and hairy dependency tree. While I can now import it
without crashes, I can't build it from the imported package definitions yet --
mainly because of lots of dependency cycles in the generated packages, but
there may be more issues hidden beneath that.

Still, I can recommend it as a test of everyone's importer patches, since
it'll find a lot of edge cases in importing alone!

> What you propose looks similar to part of the work Simon Tournier
> submitted at <https://issues.guix.gnu.org/63647>.

It seems lots of people have been working on the same problem -- in addition
to Simon's patches, I found a patch submitted by Elbek (issues 64035 & 64036;
Cc'd). I also forgot about the issue I submitted months ago (63001)...

> What would you suggest?  Simon?

Here's a brief comparison between Simon's patches and mine -- Simon's seem to
contain fixes for a couple more things than mine currently does:

1. Simon sorts available versions in an error message; this can presumably be
   merged independently since it doesn't conflict with other patches.

2. Simon always prepends a "SUBDIR/" prefix to the tag if found, whereas I try
   to find the plain "vX" tag first, then fall back to "SUBDIR/vX". Judging by
   https://go.dev/ref/mod#vcs-version, Simon's approach seems more correct.
   I'll change my implementation to match and try it out.

3. For detecting the `module-path-subdirectory' in Simon's patches: that's the
   same approach I used initially, but I found I have to try `(substring
   module-path (string-length import-prefix))' first (to handle e.g.
   cloud.google.com/go/*). This is one of the things I haven't submitted
   yet...

> Thanks for the patch, Timo!

Thanks for your work in sorting through all of this, Ludo'!

Cheers,
Timo

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