go get with branch results in 500 error

[rogpeppe]

Describe the bug
If I use go get $module@$branchname, I get a 500 response from the Athens proxy.

Error Message

go get github.com/juju/errors@master: unexpected status (http://localhost:3000/github.com/juju/errors/@v/master.info): 500 Internal Server Error

To Reproduce
Steps to reproduce the behavior:

% cd /tmp
% mkdir m
% cd m
% go mod init example.com/foo
go: creating new go.mod: module example.com/foo
% cat main.go
package main

import _ "github.com/juju/errors"

func main() {
}
% cat go.mod
module example.com/foo

go 1.12

require github.com/juju/errors v0.0.0-20180806074554-22422dad46e1
% echo $GOPROXY
http://localhost:3000
% go get github.com/juju/errors@master
go: finding github.com/juju/errors master
go: finding github.com/juju master
go: finding github.com master
go get github.com/juju/errors@master: unexpected status (http://localhost:3000/github.com/juju/errors/@v/master.info): 500 Internal Server Error

Expected behavior
I would expect this command to fetch the latest commit from the master branch of github.com/juju/errors.

Environment (please complete the following information):

• OS: Linux 64 bit
• Go version : go version devel +22dbc96d8a Tue Nov 27 09:26:16 2018 +0000 linux/amd64
• Buffalo Version : no sure how to find this out
• Proxy version : gomods/athens:v0.2.0
• Storage (fs/mongodb/s3 etc.) : fs

Docker logs:

I observed the following docker log messages when running the above script:

handler: GET /github.com/juju/errors/@v/list/ [200]
time="2018-11-27T12:37:57Z" level=error msg="not in cache" http-method=GET http-path=/github.com/juju/errors/@v/master.info http-url=/github.com/juju/errors/@v/master.info kind="Internal Server Error" module=github.com/juju/errors operation=download.VersionInfoHandler ops="[download.VersionInfoHandler pool.Info protocol.Info stash.Pool stasher.Stash stasher.fetchModule goGetFetcher.Fetch module.downloadModule]" version=master
handler: GET /github.com/juju/errors/@v/master.info [500]
time="2018-11-27T12:37:57Z" level=error msg="invalid version \"master\"" http-method=GET http-path=/github.com/juju/@v/master.info http-url=/github.com/juju/@v/master.info kind="Internal Server Error" module=github.com/juju operation=download.VersionInfoHandler ops="[download.VersionInfoHandler pool.Info protocol.Info stash.Pool stasher.Stash stasher.fetchModule goGetFetcher.Fetch module.downloadModule]" version=master
handler: GET /github.com/juju/@v/master.info [500]
time="2018-11-27T12:37:58Z" level=error msg="invalid version \"master\"" http-method=GET http-path=/github.com/@v/master.info http-url=/github.com/@v/master.info kind="Internal Server Error" module=github.com operation=download.VersionInfoHandler ops="[download.VersionInfoHandler pool.Info protocol.Info stash.Pool stasher.Stash stasher.fetchModule goGetFetcher.Fetch module.downloadModule]" version=master
handler: GET /github.com/@v/master.info [500]

[michalpristas]

Related #949

[rogpeppe]

Note that go get github.com/juju/errors did not update to the latest version either.

[marpio]

@rogpeppe this is a known limitation Documentation mentions commit hash but it applies also to branches.
What you can do is go get this module without using proxy (so GOPROXY="")
This will add something like require github.com/juju/errors v0.0.0-20181118221551-089d3ea4e4d5 // indirect to the go.mod file. The build using proxy will work because now the proxy will use the pseudo-version v0.0.0-20181118221551-089d3ea4e4d5.
Ref golang/go#27947

[rogpeppe]

FWIW the known limitation page says:

When you want to include a new library in your program by “branch”, just do go get github.com/my/pkg@master. This will put a real semver pseudo version inside your go.mod file. From that point on, you can use the GOPROXY to get the same exact version.

which sounds like the branch code works.

[marpio]

You're right, we should make the docs more explicit/clear.
go get github.com/juju/errors@master wont work if $GOPROXY env var is set. It will work though, if it's not set.
Once you have a record like this require github.com/juju/errors v0.0.0-20180806074554-22422dad46e1 in your go.mod, go will use the pseudo version while building and so athens will get requests like /github.com/juju/@v/v0.0.0-20180806074554-22422dad46e1.info which are all fine.
So to summarize:

• go get github.com/juju/errors@master will work only if GOPROXY is not set.
• go get github.com/juju/errors@v0.0.0-20180806074554-22422dad46e1 will work with GOPROXY set

[arschles]

Another useful addition would be to include the error message in the response body. When you run go get github.com/juju/errors@master against an Athens server, here's what the server logs look like:

time="2018-12-06T19:14:13Z" level=error msg="invalid version \"master\"" http-method=GET http-path=/github.com/juju/@v/master.info http-url=/github.com/juju/@v/master.info kind="Internal Server Error" module=github.com/juju operation=download.VersionInfoHandler ops="[download.VersionInfoHandler pool.Info protocol.Info stash.Pool stasher.Stash stasher.fetchModule goGetFetcher.Fetch module.downloadModule]" version=master
handler: GET /github.com/juju/@v/master.info [500]
time="2018-12-06T19:14:13Z" level=error msg="invalid version \"master\"" http-method=GET http-path=/github.com/@v/master.info http-url=/github.com/@v/master.info kind="Internal Server Error" module=github.com operation=download.VersionInfoHandler ops="[download.VersionInfoHandler pool.Info protocol.Info stash.Pool stasher.Stash stasher.fetchModule goGetFetcher.Fetch module.downloadModule]" version=master

We could return the msg (invalid version "master") to the client. That would be a good start for us

Maybe in the future we can match against this string on the server and return a 404 if we find it.....

[marpio]

We're now able to go get by branch!

[stubbornTanzhe]

We're now able to go get by branch!

is this feature merged to master branch? I checked athen docker but found not supported yet.

[marpio]

@stubbornTanzhe
Please try again, now that #1063 is merged - this fix requires go 1.12 to work properly.