panic: shouldn't be possible unable to deduce repository and source type for: "golang.org/x/sys/unix"

[bsed]

 $ dep ensure -update
panic: shouldn't be possible unable to deduce repository and source type for: "golang.org/x/sys/unix"

goroutine 1 [running]:
github.com/golang/dep/internal/gps.(*solver).selectRoot(0xc0421a4000, 0xc0420f5500, 0x1b)
        E:/gocode/src/github.com/golang/dep/internal/gps/solver.go:502 +0xb18
github.com/golang/dep/internal/gps.(*solver).Solve(0xc0421a4000, 0x12, 0xa71d00, 0xabf608, 0xc0420fbf6e)
        E:/gocode/src/github.com/golang/dep/internal/gps/solver.go:348 +0x8e
main.(*ensureCommand).Run(0xc0421484a0, 0xc04210bb40, 0xc04204e3b0, 0x0, 0x0, 0x0, 0x0)
        E:/gocode/src/github.com/golang/dep/cmd/dep/ensure.go:148 +0x389
main.(*Config).Run(0xc04200b320, 0xc04200b320)
        E:/gocode/src/github.com/golang/dep/cmd/dep/main.go:159 +0x8ba
main.main()
        E:/gocode/src/github.com/golang/dep/cmd/dep/main.go:44 +0x25a

[bsed]

sm.DeduceProjectRoot: unable to deduce repository and source type for: "golang.org/x/crypto/acme/autocert"

[sdboyer]

The ultimate reason for the error is detailed in #292, but it's not great that there's a panic case that can be triggered by this. Let's treat this issue as being about covering that panic.

[ibrasho]

Any specific error message instead of the panic?

[sdboyer]

Looking at the source line, I see it's preceded by a note from me:

// TODO(sdboyer) this could well happen; handle it with a more graceful error

So yeah 😄 Problem is, at that specific point, there are a number of things that could cause the error. Still, for now, the best thing to do is probably just return the error out directly.

[ibrasho]

Should it be handled somewhere else? Otherwise, dep will be print this error anyway:

ensure Solve(): unable to deduce repository and source type for: "golang.org/x/sys/unix"

[ibrasho]

#561 Seems like an improvement to the errors that are returned:

panic: shouldn't be possible unable to deduce repository and source type for "golang.org/x/sys/unix": unable to determine remote metadata protocol: failed to access url "http://golang.org/x/sys/unix?go-get=1"

[sdboyer]

Yes, #561 would improve the message - but it absolutely does have to return out the error, as it's not possible to continue solving if this occurs.

It could be handled earlier, e.g. in Prepare(). We'd have to iterate through each of the imports in the project, attempt deduction, and collect a slice of failures. That work should be parallelized. Kind of akin to what we do in init, but with a waitgroup and using DeduceProjectRoot() instead of SyncSourceFor().

[ibrasho]

Prepare() doesn't have access to the logger ctx.Loggers.Err unless verbose mode is toggled. Any pointers on what could be done in that case?

BTW, I noticed that Prepare() is called twice in Run() (in init.go). I'm not sure if this intentional or not.

[sdboyer]

Right, we never print anything directly from within gps. There's only one single solitary exception to that rule, and it needs to be gotten rid of, too 😄 apart from the fs funcs you're working on in the other PR, gps should be considered self-contained, and import only things at or below its level in the project.

Instead, follow the pattern that's in that function - return a badOptsFailure with an appropriate message. It's not great, but it's consistent, and good enough for now.

BTW, I noticed that Prepare() is called twice in Run() (in init.go). I'm not sure if this intentional or not.

It is - the comments say a bit about it. It's run the second time in order to get the modified input hash for the Gopkg.lock memo field.

[ibrasho]

@sdboyer Somehow this issue is not reproducible using dep v0.1.0-88-gce194b4fb9f3.

I'm getting the following error instead of a panic: ensure Solve(): unable to deduce repository and source type for "golang.org/x/sys": unable to read metadata: unable to fetch raw metadata: failed HTTP request to URL "http://golang.org/x/sys?go-get=1": Get http://golang.org/x/sys?go-get=1: dial tcp 127.0.0.1:80: getsockopt: connection refused

@bsed Could you update dep and check now?