GoImpl: support relative (vendor) imports

[boz]

This fixes :GoImpl for cases when the interface package is in vendor or similar. It depends on josharian/impl#18, which adds the -dir argument (-dir defaults to $PWD so hopefully the fallback won't be used much).

[fatih]

I'm not sure why we run another if this fails. If you could give me an example why it fails I can see why you did this. Why if we always pass the -dir? What exactly does this fix?

[boz]

• The current version of the impl command ignores vendor when finding the interface to generate. It will fail if the interface is installed in vendor but not $GOPATH.
• Support vendor imports josharian/impl#18 adds -dir <dir> to root the normal go package resolution rules at <dir>, which fixes the vendor issue. <dir> defaults to $PWD.
• The current version of impl does not take a -dir <dir> argument.

Maybe an example will help. impl.new is from josharian/impl#18 and impl.orig is the current release:

$ mkdir -p $GOPATH/src/test.com/user/vim-go-impl
$ cd $GOPATH/src/test.com/user/vim-go-impl
$ mkdir -p vendor/src/test.com/foo
$ cat > vendor/src/test.com/foo/foo.go <<EOF
> package foo
> type I interface {
>   Bar()
> }
> EOF
$ impl.orig 'i *I' foo.I
interface foo.I not found: couldn't find package src/test.com/foo: cannot find package "src/test.com/foo" in any of:
  /usr/local/Cellar/go/1.8.3/libexec/src/src/test.com/foo (from $GOROOT)
  /Users/abozanich/gopath/src/src/test.com/foo (from $GOPATH)
$ impl.new 'i *I' foo.I
func (i *I) Bar() {
  panic("not implemented")
}

$ cd ..
$ impl.new 'i *I' foo.I
unrecognized interface: foo.I
$ impl.new -dir $PWD/vim-go-impl 'i *I' foo.I
func (i *I) Bar() {
  panic("not implemented")
}

$ impl.orig -dir $PWD/vim-go-impl 'i *I' foo.I
impl <recv> <iface>

impl generates method stubs for recv to implement iface.

Examples:

impl 'f *File' io.Reader
impl Murmur hash.Hash

Don't forget the single quotes around the receiver type
to prevent shell globbing.

It runs another if it fails because I didn't want to break installs with an older impl build. Omitting the -dir <dir> is usually ok for my workflow because I'm generally cd'd into the directory that has vendor.

[arp242]

I think we can remove this workaround now that the impl PR is merged?

If you could rebase on master then I can test and merge it.

[arp242]

Could you tell me how to reproduce this issue? It's not really clear from this PR or the impl PR.

On master (without this patch) I tried using:

:GoImpl l Log github.com/sirupsen/logrus.StdLogger

Which seems to work correct?

This package is vendored for the project I have open. I made sure it's not in my regular GOPATH.

What am I doing wrong?

[boz]

@Carpetsmoker: impl defaults to -dir $PWD. I wrote an example here, take a look at what happens after the cd ...

[arp242]

Ah right, didn't see that because it was collapsed 👍