x/tools/gopls: detect tools.go files, and suppress warning

[Jyosua]

I've been looking for a way to fix this for quite a bit of time and nothing I've tried has worked. I'm using oapi-codegen to generate boilerplate for my webserver. The authors of this library recommend the tools.go pattern for managing the dependency, so that go.mod can act as the single source of truth for versioning. For transparency, their readme recommends this here. Doing this actually works -- I can run go generate just fine and my code builds. However, VSCode insists on showing an error and warning in this tools.go file, marking the file and the module folder red:

This is driving me crazy. I'd like to at least suppress these, but I can't find any way to do so. I've tried using the lintFlags to exclude it, but it appears to be gopls and not staticcheck, so this doesn't do anything. I can't find a gopls configuration setting that will allow me to ignore this file or any issues with it, either.

For what it's worth, someone else noticed the same thing with a different library in this issue.

What version of Go, VS Code & VS Code Go extension are you using?

Version Information

• Run go version to get version of Go from the VS Code integrated terminal.
  • go version go1.22.5 darwin/arm64
• Run gopls -v version to get version of Gopls from the VS Code integrated terminal.
  • golang.org/x/tools/gopls v0.16.1
• Run code -v or code-insiders -v to get version of VS Code or VS Code Insiders.
  • Version: 1.92.1
• Check your installed extensions to get the version of the VS Code Go extension
  • v0.42.0
• Run Ctrl+Shift+P (Cmd+Shift+P on Mac OS) > Go: Locate Configured Go Tools command.

# Tools Configuration


## Environment

GOBIN: undefined
toolsGopath: 
gopath: /Users/[username]/go
GOROOT: /opt/homebrew/Cellar/go/1.22.5/libexec
PATH: /opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/Users/[username]/Library/Application Support/JetBrains/Toolbox/scripts:/Users/[username]/go/bin

## Tools

	go:	/opt/homebrew/bin/go: go version go1.22.5 darwin/arm64

	gopls:	/Users/[username]/go/bin/gopls	(version: v0.16.1 built with go: go1.22.5)
	gotests:	not installed
	gomodifytags:	not installed
	impl:	not installed
	goplay:	not installed
	dlv:	/Users/[username]/go/bin/dlv	(version: v1.23.0 built with go: go1.22.5)
	staticcheck:	/Users/[username]/go/bin/staticcheck	(version: v0.4.7 built with go: go1.22.5)

## Go env

Workspace Folder (point-system): /Users/[username]/Documents/Repositories/point-system

	GO111MODULE=''
	GOARCH='arm64'
	GOBIN=''
	GOCACHE='/Users/[username]/Library/Caches/go-build'
	GOENV='/Users/[username]/Library/Application Support/go/env'
	GOEXE=''
	GOEXPERIMENT=''
	GOFLAGS=''
	GOHOSTARCH='arm64'
	GOHOSTOS='darwin'
	GOINSECURE=''
	GOMODCACHE='/Users/[username]/go/pkg/mod'
	GONOPROXY=''
	GONOSUMDB=''
	GOOS='darwin'
	GOPATH='/Users/[username]/go'
	GOPRIVATE=''
	GOPROXY='https://proxy.golang.org,direct'
	GOROOT='/opt/homebrew/Cellar/go/1.22.5/libexec'
	GOSUMDB='sum.golang.org'
	GOTMPDIR=''
	GOTOOLCHAIN='auto'
	GOTOOLDIR='/opt/homebrew/Cellar/go/1.22.5/libexec/pkg/tool/darwin_arm64'
	GOVCS=''
	GOVERSION='go1.22.5'
	GCCGO='gccgo'
	AR='ar'
	CC='cc'
	CXX='c++'
	CGO_ENABLED='1'
	GOMOD='/dev/null'
	GOWORK=''
	CGO_CFLAGS='-O2 -g'
	CGO_CPPFLAGS=''
	CGO_CXXFLAGS='-O2 -g'
	CGO_FFLAGS='-O2 -g'
	CGO_LDFLAGS='-O2 -g'
	PKG_CONFIG='pkg-config'
	GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/by/cxzl4qc57c3c8dd9p9snhn680000gn/T/go-build3419525479=/tmp/go-build -gno-record-gcc-switches -fno-common'

Share the Go related settings you have added/edited

{
    "go.lintTool": "staticcheck",
    "go.lintFlags": [
        "-exclude=gateway/tools/tools.go"
    ]
}

[hyangah]

Yes, the error and warning messages come from the gopls (the language server).
Since the tools.go file has //go:build tools build tag, gopls processes and analyzes the file only it is open. The diagnostics will disappear as soon as you close the tools.go file.

The warning message ("No packages found for open file ...") seems intentional, but I think we can consider different wording and info-level.

The error message ("import X is a program, not an importable package") is not great for tools.go style dependency management practice. Can we teach gopls this special case and suppress this specific error message?

cc @findleyr

[findleyr]

I'd be happy to accept a change suppressing errors that match this pattern. The heuristic seems accurate enough. Moving this to the Go issue tracker as a gopls issue.

A couple quick notes:

• this error is from go list, by way of go/packages, which means it needs to be suppressed when processing go list errors, for example here
• the warning only appears if the file is open, which is probably benign enough. However, if we have a heuristic for detecting a tools.go file, perhaps we could suppress all other diagnostics, and have an information diagnostic explaining that this file is not considered for builds, and linking to some documentation (or even just this issue)