x/tools/gopls: show diagnostic for for circular dependency

[inliquid]

VS Code. Say, we have a circular dependency. In this case go vet would warn that it's not allowed. However it seems that gopls doesn't check this and just stops working (not providing hover outputs, references, what so ever) with these non-informative errors in output:

[Error - 21:27:10] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:10] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:10] Request textDocument/hover failed.
  Message: no AST for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go
  Code: 0 
[Error - 21:27:12] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:13] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:13] Request textDocument/definition failed.
  Message: no AST for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go
  Code: 0 
[Error - 21:27:13] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:14] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:14] Request textDocument/hover failed.
  Message: no AST for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go
  Code: 0 
[Error - 21:27:15] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:16] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:16] Request textDocument/definition failed.
  Message: no AST for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go
  Code: 0 
[Error - 21:27:16] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:17] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:17] Request textDocument/hover failed.
  Message: no AST for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go
  Code: 0 
[Error - 21:27:18] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:18] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:18] Request textDocument/definition failed.
  Message: no AST for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go
  Code: 0 
[Error - 21:27:19] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:20] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking
[Error - 21:27:20] no highlight for c:\Users\***\go\src\path\to\workdir\pkg\client\ui\ui.go:21:25: no AST for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go
[Error - 21:27:21] unable to check package for file:///c:/Users/***/go/src/path/to/workdir/pkg/client/ui/ui.go: package path/to/workdir/pkg/client/ui has errors, skipping type-checking

[stamblerre]

Good catch, thank you for noticing this. You are right, gopls will not even bother to check your package if it notices a circular dependency (https://github.com/golang/tools/blob/d5f455491e2f028578d3349b43426ca65e2e0ee0/internal/lsp/cache/check.go#L51), so we should show a diagnostic for those cases.

[jbszczepaniak]

I would like to claim this one ;)

[stamblerre]

Great! Let me know if you need any advice on how to tackle it, or please feel free to reach out to me directly on Gophers Slack.

[jbszczepaniak]

As @stamblerre suggested I will take something easier for first task. Leaving this for now.

[gopherbot]

Change https://golang.org/cl/209857 mentions this issue: internal/lsp: add error handling for self imports

[ridersofrohan]

After #35964 gets fixed. We need to adjust/write the diagnostic tests inside (tools/internal/lsp/testdata/circular/) to test the behavior and ensure that it is working.

[gopherbot]

Change https://golang.org/cl/210942 mentions this issue: internal/lsp: add diagnostic on import causing import cycle