x/tools/gopls: excessive packages.Load calls with an ad-hoc package outside of GOPATH/module

[RomanKornev]

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

• Run go version to get version of Go
  • go version go1.15.2 darwin/amd64
• Run gopls -v version to get version of Gopls if you are using the language server.
  • golang.org/x/tools/gopls v0.5.3
    golang.org/x/tools/gopls@v0.5.3 h1:C8QSrqjqaVzlVoHL1R9yWbROoOApRgI8gN1G+cHlPuw=
    github.com/BurntSushi/toml@v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
    github.com/google/go-cmp@v0.5.1 h1:JFrFEBb2xKufg6XkJsJr+WbKb4FQlURi5RUcBveYu9k=
    github.com/sergi/go-diff@v1.1.0 h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0=
    golang.org/x/mod@v0.3.0 h1:RM4zey1++hCTbCVQfnWeKs9/IEsaBLA8vTkd0WVtmH4=
    golang.org/x/sync@v0.0.0-20201020160332-67f06af15bc9 h1:SQFwaSi55rU7vdNs9Yr0Z324VNlrF+0wMqRXT4St8ck=
    golang.org/x/tools@v0.0.0-20201110032815-ae45d7cf37a9 h1:S0ATUNSw92bO7f5Z+1tSQsq48TdQs2Ye2rTGJdtf5qc=
    golang.org/x/xerrors@v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
    honnef.co/go/tools@v0.0.1-2020.1.6 h1:W18jzjh8mfPez+AwGLxmOImucz/IFjpNlrKVnaj2YVc=
    mvdan.cc/gofumpt@v0.0.0-20200927160801-5bfeb2e70dd6 h1:z+/YqapuV7VZPvBb3GYmuEJbA88M3PFUxaHilHYVCpQ=
    mvdan.cc/xurls/v2@v2.2.0 h1:NSZPykBXJFCetGZykLAxaL6SIpvbVy/UFEniIfHAa8A=
• Run code -v or code-insiders -v to get version of VS Code or VS Code Insiders
  • 1.51.1
• Check your installed extensions to get the version of the VS Code Go extension
  • 0.18.1
• Run go env to get the go development environment details
  • GO111MODULE=""
    GOARCH="amd64"
    GOBIN=""
    GOCACHE="/Users/df/Library/Caches/go-build"
    GOENV="/Users/df/Library/Application Support/go/env"
    GOEXE=""
    GOFLAGS=""
    GOHOSTARCH="amd64"
    GOHOSTOS="darwin"
    GOINSECURE=""
    GOMODCACHE="/Users/df/go/pkg/mod"
    GONOPROXY=""
    GONOSUMDB=""
    GOOS="darwin"
    GOPATH="/Users/df/go"
    GOPRIVATE=""
    GOPROXY="https://proxy.golang.org,direct"
    GOROOT="/usr/local/Cellar/go/1.15.2/libexec"
    GOSUMDB="sum.golang.org"
    GOTMPDIR=""
    GOTOOLDIR="/usr/local/Cellar/go/1.15.2/libexec/pkg/tool/darwin_amd64"
    GCCGO="gccgo"
    AR="ar"
    CC="clang"
    CXX="clang++"
    CGO_ENABLED="1"
    GOMOD=""
    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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/gd/ck6ncspn19115_7mxytyzw840000gp/T/go-build473384269=/tmp/go-build -gno-record-gcc-switches -fno-common"

Share the Go related settings you have added/edited

"go.useLanguageServer": true,

Describe the bug

When I save a file, it automatically adds any used package to import section. When that happens, I get a phantom error:

	"owner": "_generated_diagnostic_collection_name_#0",
	"severity": 8,
	"message": "could not import fmt (no package for import fmt)",
	"source": "compiler",

I still compiles, and if I comment/uncomment the import, the error goes away, but it's still very annoying.

Steps to reproduce the behavior:

1. Paste following code - no errors

package main

import (
	"fmt"
)

func main() {
	fmt.Println(10)
}

2. Remove line 8 and save a file - no errors
3. Undo once - no errors
4. Undo again - no errors
5. Save a file - error above
6. Add any code below the import - error still present
7. Comment/uncomment import - error is gone

Screenshots or recordings

[stamblerre]

Can you please share a gopls log from when you see this happen? Instructions on how to capture a log are here: https://github.com/golang/tools/blob/master/gopls/doc/troubleshooting.md#capturing-logs.

[RomanKornev]

Here's the log:
gopls.log

[stamblerre]

It looks like you delete and then replace the full content of the file in this log. My guess is that this is a bug that is actually fixed in Go 1.16. If you're willing to try building Go 1.16 from source, you can confirm that way (https://golang.org/doc/install/source).

Another way to test this out would be to add something like os.Exit(0) to your main function after and hit save. If things go back to working after that, then this bug has already been fixed in 1.16.

[RomanKornev]

Adding os.Exit(0) did not fix the issue.
Here's me reproducing it on WSL Ubuntu as well. First time it worked fine, but second time it failed to import. As you can see, I'm not replacing the whole file:

go version go1.15.5 linux/amd64
golang.org/x/tools/gopls v0.5.3
win10_wsl.log

[stamblerre]

Thanks for the update. It's still a little tricky to see exactly what's going on here, so I will now have to ask you to try reproducing with Go 1.16. Since it's not yet released, you will have to follow the steps for building Go from source here: https://golang.org/doc/install/source.

If the issue persists with Go 1.16, then there is probably a gopls bug somewhere here.

[stamblerre]

One thing to note is that you may be able to resolve the problem by creating a module (go mod init) in this directory. I believe there is a bug here with the way this package is being treated since it is both outside of GOPATH and outside of a module. I will also check if I can reproduce this myself with Go 1.15.

[RomanKornev]

Seems to be fixed in 1.16. Unable to reproduce on go version devel +926994fd7c Thu Nov 26 21:10:09 2020 +0000 darwin/amd64

[gopherbot]

Change https://golang.org/cl/274443 mentions this issue: internal/lsp: don't reload invalid build configurations unconditionally

[gopherbot]

Change https://golang.org/cl/275436 mentions this issue: internal/lsp: don't reload invalid build configurations unconditionally