cmd/go: go mod init does not correctly resolve pseudo-versions

[rogpeppe]

What version of Go are you using (go version)?

$ go version
go version devel +ab724d43ef Mon May 20 20:58:14 2019 +0000 linux/amd64

What did you do?

Extract the following files:

-- glide.lock --
imports:
- name: github.com/Shopify/sarama
  version: 4602b5a8c6e826f9e0737865818dd43b2339a092
  subpackages:
  - mocks
- name: github.com/eapache/queue
  version: 093482f3f8ce946c05bcba64badd2c82369e084d
-- glide.yaml --
package: example

-- main.go --
package main

import (
	_ "github.com/Shopify/sarama"
	_ "github.com/eapache/queue"
)

func main() {}

Run go mod init example.

What did you expect to see?

I would expect to see the go.mod file reflect the requirements listed in the glide.lock file. Specifically, I'd expect to see this go.mod file:

module example

require (
	github.com/Shopify/sarama v1.21.0
	github.com/eapache/queue v1.1.1-0.20180227141424-093482f3f8ce
)

go 1.13

which is what you get if you start with this go.mod file, which exactly reflects the glide.lock file:

module example

go 1.12

require (
	github.com/eapache/queue 093482f3f8ce946c05bcba64badd2c82369e084d
	github.com/Shopify/sarama 4602b5a8c6e826f9e0737865818dd43b2339a092
)

What did you see instead?

I see this go.mod file:

module example

go 1.13

require (
	github.com/Shopify/sarama v1.21.0
	github.com/eapache/queue v0.0.0-20180227141424-093482f3f8ce
)

The github.com/eapache/queue dependency has the wrong pseudo-version, which means that when dependencies are later resolved, the dependency in sarama (which depends on epache/queue v1.1.0) supercedes the dependency in the go.mod file, which leads to a version regression.

[myitcv]

cc @bcmills @jayconrod

[cuonglm]

Seems duplicated of #29262

[rogpeppe]

@cuonglm I don't think it's a duplicate of that #29262. With that bug, I can do go get rsc.io/quote@5d9f230bcfba and version stays at v0.0.0-20180710144737-5d9f230bcfba, whereas with this bug, if I do go get github.com/eapache/queue@093482f3f8ce, the version changes to the correct v1.1.1-0.20180227141424-093482f3f8ce.

[bcmills]

Neat example. I can confirm the observed behavior: go mod init produces the wrong pseudo-version, but go get finds the correct one.

[gopherbot]

Change https://golang.org/cl/178497 mentions this issue: cmd/go: fix go mod init resolve wrong pseudo-version

[thepudds]

https://golang.org/cl/178497 I think is trying to get go mod init to create the proper pseudoversion.

If that turns out to be tricky to get right or a bigger change than would work for 1.13, I wonder if an alternative approach might be to simplify what go mod init tries to do in this case.

Instead of go mod init creating the proper pseudoversion, perhaps instead go mod init could just leave the commit hash in the resulting go.mod file?

That should then be automatically converted to the right pseudoversion by the first go list -m all, go build or similar because the commit hash would be treated as a "module query".

However, perhaps that is no simpler than the current https://golang.org/cl/178497 approach.

[cuonglm]

@thepudds I don't know why that change is not sure or hard to understand. When the convert try to make pseudoversion, it does use statVers to query the most recent tag:

// Otherwise make a pseudo-version.
if info2.Version == "" {
        tag, _ := r.code.RecentTag(statVers, p)
        v = tagToVersion(tag)
        // TODO: Check that v is OK for r.pseudoMajor or else is OK for incompatible.
        info2.Version = PseudoVersion(r.pseudoMajor, v, info.Time, info.Short)
}

we passed statVers as empty string, so most recent tag from HEAD was returned instead of most recent tag from commit.

[gopherbot]

Change https://golang.org/cl/179857 mentions this issue: cmd/go/internal/modfetch: use the resolved version to search for tags in (*codeRepo).convert

[bcmills]

It is not correct for convert to use statVers in the RecentTag lookup, but passing in the correct rev moves things in the right direction regardless.