support go.mod replace version pinning

[jpughcs]

Fix for error caused by replace directives with version pinning:

2020/08/06 10:53:59 [INFO] Temporary folder: /go/src/x/y/service/cta-proxy/buildenv_2020-08-06-1053.131880924
2020/08/06 10:53:59 [INFO] Writing main module: /go/src/x/y/service/cta-proxy/buildenv_2020-08-06-1053.131880924/main.go
2020/08/06 10:53:59 [INFO] Initializing Go module
2020/08/06 10:53:59 [INFO] exec (timeout=10s): /usr/local/bin/go mod init caddy 
go: creating new go.mod: module caddy
2020/08/06 10:53:59 [INFO] Replace x/y => /go/src/x/y
2020/08/06 10:53:59 [INFO] exec (timeout=10s): /usr/local/bin/go mod edit -replace x/y=/go/src/x/y 
2020/08/06 10:53:59 [INFO] Replace github.com/apache/thrift => github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02
2020/08/06 10:53:59 [INFO] exec (timeout=10s): /usr/local/bin/go mod edit -replace github.com/apache/thrift=github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02 
go mod: -replace=github.com/apache/thrift=github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02: invalid new path: malformed import path "github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02": invalid char ' '
2020/08/06 10:53:59 [ERROR] exit status 1

[mholt]

Thanks, but I don't think I can accept this as-is. I'm not even aware of any problems in xcaddy right now.

What is the problem? You'll have to motivate the reason for this change.

[jpughcs]

My apologies, I should have created a formal issue first...

Expected Behavior

Using a replace directive in go.mod with a versioned pinned ModulePath should correctly execute go mod edit -replace with the given replacement during buildenv initialization.

go.mod:

replace github.com/apache/thrift => github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02

buildenv initialization:

[INFO] exec (timeout=10s): /usr/local/bin/go mod edit -replace github.com/apache/thrift=github.com/apache/thrift@v0.0.0-20190309152529-a9b748bb0e02

Current Behavior

go.mod:

replace github.com/apache/thrift => github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02

buildenv initialization:

[INFO] Replace github.com/apache/thrift => github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02
[INFO] exec (timeout=10s): /usr/local/bin/go mod edit -replace github.com/apache/thrift=github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02 
go mod: -replace=github.com/apache/thrift=github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02: invalid new path: malformed import path "github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02": invalid char ' '

Note the space in the replacement directive between the new ModulePath and Version. xcaddy currently builds the mod edit -replace command from these ModulePaths verbatim. This is incompatible with the mod edit -replace command as it requires there to be an @ symbol between the ModulePath and Version.

Steps to Reproduce

1. Add a version pinned replacement directive to go.mod
2. Run an xcaddy command that initializes a buildenv

[mholt]

What is your xcaddy command though? Like, how can I reproduce the problem? I use --replace all the time and it works fine.

[jpughcs]

I am running simply xcaddy and xcaddy list-modules. The output in my first comment, yesterday, was from running xcaddy list-modules.

[jpughcs]

This is what xcaddy is trying to run with my replace directive in go.mod:

go mod edit -replace 'github.com/apache/thrift=github.com/apache/thrift v0.0.0-20190309152529-a9b748bb0e02'

If you run that manually, you will see the same error invalid char ' '

However,

go mod edit -replace 'github.com/apache/thrift=github.com/apache/thrift@v0.0.0-20190309152529-a9b748bb0e02'

... works, but there is nothing currently in xcaddy, that I can tell, which reformats the components of the replace directive like this.

[mholt]

I see. I usually use replace for local copies, like:

replace github.com/caddyserver/certmagic => ../certmagic

And so there is no version string.

What is the use case for replace with a version string, rather than simply using go get (i.e. changing the version in go.mod's require statement)?

[mholt]

Elegant fix though, thanks for the test cases too!

[mholt]

I don't think there's any need for regular expressions, and we can't assume the version starts with v (it could be a commit or branch name):

Suggested change

	if r == "" {
	return ""
	}
	return regexp.MustCompile(`\sv`).ReplaceAllString(string(r), "@v")
	return strings.Replace(string(r), " ", "@", 1)

[jpughcs]

From what I understand, the "version" here will always start with a v. See: https://golang.org/ref/mod#versions

[mholt]

We can try it, but go get accepts commits and branches too.

Make this change anyway (with a v if you want) and I can merge this.

[jpughcs]

What is the use case for replace with a version string, rather than simply using go get (i.e. changing the version in go.mod's require statement)?

See:
uber-go/cadence-client#523
uber-go/cadence-client#812

Quite an annoying problem...

[mholt]

Cool, thanks for the fix! This works for you then?

[jpughcs]

Yes this works. Thank you! 😃

[mholt]

Okay, thanks again! (I just pushed a couple minor tweaks.) I appreciate the contribution!