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.