autocomplete unimported packages

[lloiser]

This is done by (temporarily) adding an import "..." statement into the code so that gocode can find the package and provide suggestions for it.

It is still rough on the edges especially for vendored packages.

Possible improvements:

• automatically add the import "..." when a suggestion is selected (nice to have, will be added by goimports on save anyway)
• the pkg map in go.js does not grow if new packages are added (low prio)

Fixes #665

[zmb3]

Have you considered gopkgs instead of go list? It reads $GOPATH/pkg instead of $GOPATH/src and is orders of magnitude faster.

[lloiser]

Nice! I will check it out.

[lloiser]

I choose gopkgs atm even though it does not resolve the actual package name but only the folder its in.
microsoft/vscode-go#647 shows that this can be an issue we will face sooner or later.

[lloiser]

@zmb3 or @joefitzgerald can anybody pls review this 😁

[zmb3]

Can we add a spec with a fixture that doesn't import a package to actually flesh this out?

[zmb3]

This looks pretty similar to the locator code. Can we reuse any of that? Are we duplicating work here?

[joefitzgerald]

Thanks @lloiser!!