cmd/go: unhelpful error message from go get when custom import has moved

[robpike]

% go get -u rsc.io/github/issue
package rsc.io/github/issue
imports 9fans.net/go/acme
imports 9fans.net/go/plan9
imports 9fans.net/go/plan9/client
imports 9fans.net/go/draw
imports 9fans.net/go/draw/drawfcall
imports github.com/google/go-github/github
imports github.com/google/go-querystring/query
imports golang.org/x/oauth2
imports golang.org/x/net/context: /Users/r/src/golang.org/x/net is from https://code.google.com/p/go.net, should be from https://go.googlesource.com/net

The error is the last line, but "should be" doesn't tell me much, as this is a transitive dependency I don't know about. It should say something about what went wrong (vanity import has changed target) or how to fix it (remove stale repo) or .... ?

I found this difficult to understand but easy to fix, implying the error message could be improved.

[rsc]

We don't know exactly what went wrong. We can't say that the custom import changed target, because maybe it was never code.google.com/p/go.net and you just happened to run an hg command to populate /Users/r/src/golang.org/x/net from there. We could suggest removing the directory and re-running go get, but that assumes there are no changes that need to be kept. I am always wary of tools suggesting that people remove directories: people will do it blindly.

We could make the error more explicit about the operations, saying

imports golang.org/x/net/context: /Users/r/src/golang.org/x/net is checked out from https://code.google.com/p/go.net, but golang.org/x/net should be checked out from https://go.googlesource.com/net

Is that enough to make the problem clearer?

[adg]

Perhaps the message should say why "golang.org/x/net should be checked out from xxx". Otherwise it's like "uhh, but why should it be checked out from there?"

[rsc]

golang.org/x/net is a custom import path for https://go.googlesource.com/net, but /Users/r/src/golang.org/x/net is checked out from https://code.google.com/p/go.net
?

[adg]

That's much clearer IMO. LGTM.

On 14 January 2015 at 14:50, Russ Cox notifications@github.com wrote:

golang.org/x/net is a custom import path for
https://go.googlesource.com/net, but /Users/r/src/golang.org/x/net is
checked out from https://code.google.com/p/go.net
?

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#9540 (comment).

[rsc]

Fixed but forgot to write the magic line. https://golang.org/cl/2808