x/tools/gopls: completion doesn't work correctly in some conditions

[worlpaker]

gopls version

v0.14.2

go env

set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\worlpaker\AppData\Local\go-build
set GOENV=C:\Users\worlpaker\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\worlpaker\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\worlpaker\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\Program Files\Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLCHAIN=auto
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.21.6
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=NUL
set GOWORK=
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=C:\Users\worlpaker\AppData\Local\Temp\go-build2689359370=/tmp/go-build -gno-record-gcc-switches

What did you do?

Completion doesn't work correctly in some conditions.

variable completion after comma:

package main

func main(){
	minimum, maximum := 0, 0
	minimum, max
}

Demonstration

test.mp4

What did you see happen?

The completion of max became maxmaximum.

What did you expect to see?

The completion for max should be maximum.

Editor and settings

No response

Logs

No response

[worlpaker]

This also happens when the source code has syntax errors: missing a comma inside parentheses or accidentally putting a comma inside parentheses.

missing comma:

package main

import "fmt"

func main() {
	value := 0
	fmt.Println("value:" val)
}

The completion for val will be valvalue.

accidentally putting comma:

Similar issue from #58833

package main

import (
	"fmt"
	"math"
)

func main() {
	math.Sqrt(,0)
	math.ab
}

The completion for math.ab will be math.abmath.Abs().

[gopherbot]

Change https://go.dev/cl/561417 mentions this issue: gopls/internal/golang/completion: fix completion behavior when the source has syntax errors

[findleyr]

Thank you. This looks like a duplicate of #58833, right?

Thanks for digging into this and working on a fix! As commented on the CL, it would be helpful to explain a theory of how to handle syntax errors.

[worlpaker]

Yes, it is. Although the first scenario (max<>) logically doesn't have any syntax errors.

[findleyr]

Thanks. For what it's worth, the first scenario does have syntax errors (e.g. https://go.dev/play/p/lVxgY6Dczjf notes a syntax error).

[findleyr]

I will take a look at the fix. We can keep this issue open since the other issue is about go/parser.