Thank you for filing a gopls issue! Please take a look at the Troubleshooting guide, and make sure that you have provided all of the relevant information here.

I don't use lsp-mode, but maybe this:

https://github.com/emacs-lsp/lsp-mode/blob/master/lsp-go.el#L145-L148

is what you want?

I don't use lsp-mode, but maybe this:

https://github.com/emacs-lsp/lsp-mode/blob/master/lsp-go.el#L145-L148

is what you want?

I have set it to nil. It had no effect. Then in lsp-mode.el I see that it is not used for gopls client. It is only used for the other two: bingo and go-langserver.

https://github.com/emacs-lsp/lsp-mode/blob/6113e321b107915375e7f3fa8e9f85242f7fc874/lsp-go.el#L87

I don't think there is a way to disable diagnostics. You can set (setq lsp-diagnostic-package :none) in lsp-mode, but I don't think that will stop diagnostics from being generated or sent.

Can you give more details on the lag you are seeing? How big is your workspace? Is gopls using a lot of CPU? How did you determine there are too many diagnostics? Do you have RPC debugging enabled in Emacs (printing out all the back-and-forth kills performance in Emacs)?

I used to use gocode with company-go in emacs before. It works well and smoothly. But it is not supported now. So I switched to lsp-mode.

I have used lsp-mode for saveral monthes. It never works smoothly. The lag includes two:

1. There is a delay before completion menu popups.
2. There is a delay before I can input next char.

The cpu usage just now:

1. emacs: 99%
2. gopls: 34%

My workspace contains about 20 files. But it imports many packages.

I have added some debug message in lsp-mode.el and see that, there are ten of more lsp messages arrived after I input one char in go-mode buffer. Only one of them is completion result. All others are diagnostics messages and most of them are not for the file I'm editing and most of them are empty.

lsp-mode has to parse all of the above messages after user inputs every char. I think this may be the cause of the lag. So I want to disable diagnostic.

Or is it possible for gopls to only publish diagnostics for the file is being edited?

@netjune: What version of gopls are you using (gopls version)? Diagnostics should be cached so you shouldn't be getting this many.

I'm using gopls 0.2.2.

golang.org/x/tools/gopls 0.2.2
    golang.org/x/tools/gopls@(devel)

The 0.3.3 crashes for one of my workspace. So I go back to 0.2.2.

We're not supporting gopls/v0.2.2 because future versions have significant improvements. Would you be willing to share your gopls logs for v0.3.3 so we can help investigate the issue? Details on how to capture logs can be found here: https://github.com/golang/tools/blob/master/gopls/doc/troubleshooting.md#capturing-logs.

It crashes occasionally. And I don't work on that workspace now. I will do it when I go back to that workspace.

I'm using v0.3.4 now. It doesn't crash until now. Maybe the crash bug in 0.3.3 has been fixed in 0.3.4.

With 0.3.4 there is another problem. There are too many window/logMessage messages which make emacs lag. There are about 400 messages during one second.

See https://github.com/netjune/temp_files/blob/master/gopls-3.log

Beside the lag, I still want an option to turn off diagnostics.

I have a directory where I put all my small demo apps. They have names like: demo_foo.go, demo_bar.go... Each of them is a standalone app which has a main function. And they have many global variables and functions with same name. Then the diagnostics is not too usefull. I want to turn off it.

Change https://golang.org/cl/226371 mentions this issue: internal/lsp: avoid logging context cancellation

With 0.3.4 there is another problem. There are too many window/logMessage messages which make emacs lag. There are about 400 messages during one second.

See https://github.com/netjune/temp_files/blob/master/gopls-3.log

Thanks for reporting this! I just mailed a change that should remove those extra log lines.

Beside the lag, I still want an option to turn off diagnostics.

I have a directory where I put all my small demo apps. They have names like: demo_foo.go, demo_bar.go... Each of them is a standalone app which has a main function. And they have many global variables and functions with same name. Then the diagnostics is not too usefull. I want to turn off it.

As @muirdm said, this is not possible as a configuration through gopls, but you can try the setq lsp-diagnostic-package :none) setting. I'm going to close this issue because it's not something we will be handling in gopls itself.