x/tools/gopls: duplicate initial diagnostics sent for a file containing an error

[myitcv]

What version of Go are you using (go version)?

$ go version
go version devel +5c6f42773c Thu Dec 19 22:16:18 2019 +0000 linux/amd64
$ go list -m golang.org/x/tools
golang.org/x/tools v0.0.0-20191219230827-5e752206af05
$ go list -m golang.org/x/tools/gopls
golang.org/x/tools/gopls v0.1.8-0.20191219230827-5e752206af05

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/myitcv/.cache/go-build"
GOENV="/home/myitcv/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/myitcv/gostuff"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/myitcv/gos"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/myitcv/gos/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/myitcv/gostuff/src/github.com/myitcv/govim/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build523619605=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Using govim, open main.go:

package main

blah

func main() {
}

Observe there are two identical (other than the version number) PublishDiagnostic notifications for main.go

fail.log

What did you expect to see?

Only one PublishDiagnostic notification for main.go because the diagnostics have not changed.

What did you see instead?

Per above.

This was spotted as part of govim/govim#637

---

cc @stamblerre

[stamblerre]

Yeah, this is a result of the initial workspace load sending diagnostics for files, followed by the didOpen for the specific file. My reasoning was that we should probably always send a diagnostic for a file after you open it, even if you've already sent the diagnostic before. I'm not sure if that's necessarily correct, but it seemed reasonable to me.

[myitcv]

My reasoning was that we should probably always send a diagnostic for a file after you open it, even if you've already sent the diagnostic before.

Can you expand on why?

The client already has the diagnostics and so if they haven't changed, there's nothing to do no?

[stamblerre]

I think for me it's a combination of version information / the confirmation that the file has been opened. All prior diagnostics will have been sent for an unspecified version of the file, whereas when the client sends the first version on didOpen we will now have a version to reply with. For the gopls check command, we decided that this command is completed once we get a reply of diagnostics for the version of the file we specified, and I don't think that's an unreasonable use case.

[myitcv]

All prior diagnostics will have been sent for an unspecified version of the file, whereas when the client sends the first version on didOpen we will now have a version to reply with

👍 - that's a great point, had totally forgotten that.

we decided that this command is completed once we get a reply of diagnostics for the version of the file we specified

👍 - that also makes complete sense.

In which case, on the basis it doesn't make sense to send initial diagnostics for files where there are no errors (would also be a potentially large overhead too), I'll close this issue. i.e. we'll fix our expectations on the govim side.

Thanks very much for the detail.

cc @findleyr given our conversation by email

[myitcv]

Actually, re-opening to clarify one point. Seemingly the initial diagnostics do not include staticcheck errors.

@stamblerre can you clarify what we can expect in the initial diagnostics?

[myitcv]

One other slight vagary related to that last question: if there are two files, both of which only have go/analysis warnings, it seems that no initial diagnostics are sent, but also that on opening the first file, diagnostics (including the warnings) for both files are sent.

Getting some clarification here will help with the govim integration tests.