Use gopls rather than godoctor for extract refactorings

[sorenisanerd]

Is your feature request related to a problem? Please describe.
If a project uses go.mod mode, the extract refactorings don't work as it depends on godoctor which does not yet support modules.

Describe the solution you'd like
gopls now supports these extract refactorings. The vscode plugin should use that instead of godoctor.

Describe alternatives you've considered
There's work in progress to make godoctor support modules, but a) it has stalled and b) since gopls provides the functionality it makes sense to use that instead.

Additional context
The most recent releases(s?) of gopls has this functionality, so we should be able to safely rely on it.

[hyangah]

@sorenh thanks! Yes, that's the directory we are heading. I was told both extract function and extract variable features are available since gopls v0.4.4.

Some prerequisite decision making necessary before transitioning to gopls

• gopls refactoring feature is already available through Code Action -> Command.
  Do we want to keep Go: Extract to function and Go: Extract to variable commands?
  Note: if shortcut or keybinding is necessary, custom keybinding on code action is already possible.

• If the answer is yes, we need to sort out x/tools/gopls: provide a way to run ExecuteCommand features in one step go#40438.

• If the answer is no, we need to disable (or remove) the commands when gopls is used. But without improvements in LSP (Allow CodeActions to specify cursor position microsoft/language-server-protocol#724, How can a server implement "extract method" (how can it trigger rename?) microsoft/language-server-protocol#764, ...), it will be still somewhat different user experience.

I am leaning towards dropping the commands and waiting for the LSP improvement.

/cc @joshbaum @stamblerre

[sorenisanerd]

If I invoke the "Source Action" command, I'm told "No source actions available". What am I doing wrong? "gopls version" tells me I'm running version 0.4.4.

[stamblerre]

@sorenh: If you highlight a range of text, you should see a lightbulb appear with a suggestion to "Extract to function". Does that work?

[sorenisanerd]

@stamblerre Nope. It does for e.g. Typescript (check with the vscode source).

[sorenisanerd]

@stamblerre Er... Now it does. I have absolutely no clue what I changed. I opened the "Typescript" output as well as the "gopls" and "gopls (server)" outputs to see if that might give me some clues. When I looked at my own source code, the light bulb was there.

[sorenisanerd]

@stamblerre I just tried with code-insiders. Didn't do anything at all and now it works. I'm so confused.

[stamblerre]

Hm..not sure what was going on there, but glad it works now!
@hyangah: Do we want to keep this issue open to track deprecating the existing commands or is this good to close?

[hyangah]

I will close this bug now and track the command migration separately.