Incorrect import by auto-complete when pkgname != last part of pkg path

[AlekSi]

That's a continuation of #613. Get code from https://github.com/AlekSi/vscode-bug and then edit main.go as shown:

Two things are wrong after hitting Enter:

1. It adds sarama.v1 to code. As I explained in Format removes imports of vendored packages in use #613, the package name is sarama, not sarama.v1. Package name != last part of import path.
2. It adds vendor/gopkg.in/Shopify/sarama.v1 which is incorrect import path. vendor/ is treated differently by Go toolchain. goreturns does the right thing:

$ goreturns -d src/bugger/cmd/bugger/main.go
diff src/bugger/cmd/bugger/main.go gofmt/src/bugger/cmd/bugger/main.go
--- /var/folders/fl/c3xvc0tj1js__3jnrnbkjll40000gn/T/gofmt002523159	2016-11-24 16:22:09.000000000 +0300
+++ /var/folders/fl/c3xvc0tj1js__3jnrnbkjll40000gn/T/gofmt440158346	2016-11-24 16:22:09.000000000 +0300
@@ -1,5 +1,7 @@
 package main

+import sarama "gopkg.in/Shopify/sarama.v1"
+
 func main() {
 	sarama.V0_10_0_0
 }

[ramya-rao-a]

@AlekSi There are 2 separate things at play here.

• Auto-complete completes sara to sarama.v1 instead of sarama. This will happen to all packages from gopkg.in due to the versioning supported there.
• vendor included in the import path. This will happen only when the vendor folder is the immediate child of $GOPATH/src.

For the first issue, I have a PR out: #659

For the second, I am curious. Is it very common to have the vendor folder right under #GOPATH/src ?
Most of the projects I have seen, have the vendor folder under the Go project.

[AlekSi]

Auto-complete completes sara to sarama.v1 instead of sarama. This will happen to all packages from gopkg.in due to the versioning supported there.

It has nothing to do with v1 and gopkg.in. For example, try with go-xerial-snappy:

As mentioned several times before, package name is defined by package clause in source code, not by last component of import path. cb0d2bc is incorrect.

[ramya-rao-a]

@AlekSi First off, thanks for your patience.

I now understand that the last element in the import path need not always be the package name. It is just convention for predictability's sake that most of the time the package name is the same as the last element in the import path.

The list of packages that appear in the auto-complete comes from the output of the gopkgs tool which simply returns the import paths to all the packages in $GOPATH/pkg folder. The extension tries to fetch the package name from these import paths and has no knowledge of the source code of the packages themselves.

go list all on the other hand can return package names along with import paths as well.
gopkgs was preferred over running go list all as the latter was slow in comparision

The difference of go list all and gopkgs is that go list all looks for go packages in your $GOPATH/src while gopkgs looks in your $GOPATH/pkg. As a result of this, only importable packages that have been installed (either by go get or go install) are listed by gopkgs.

We could try out a few options and compare performance

• Use go list -f '{{ .Name }} {{ .ImportPath }}' all
• Use gopkgs and feed the output to go list -f '{{ .Name }} {{ .ImportPath }}' space-separated-output-from-gopkgs
• Update gopkgs to do second option above and return both name and import path

Until then, I would keep the fix in cb0d2bc because it atleast takes us one step closer to the ideal solution where versioned packages from gopkg.in will get the package name without the version number.

Thoughts?

[AlekSi]

I think a long-term solution would be to import packages normally, without relying on gopkgs (which does not work correctly in this case), and keep them in memory in the long-running process (gocode? Go language server? something new?).

And thank you for all your work on this extenstion. I'm in love with it. ❤️

[ramya-rao-a]

Language server is a good idea here.

For now, I have a working solution where I am thinking of doing the below

• go list -f {{.Name}};{{.ImportPath}} all runs once on extension activation (like when you open a new VS Code window)
• Form mapping between package import path and package name from the above output.
• Use this for the auto-completion

And thanks for your kind words. I'll try and keep up the good work :)

[ramya-rao-a]

The fix for this issue is now out in the latest update (0.6.63) to the Go extension

Thanks for your patience @AlekSi, I know this took a while :)