x/tools/gopls: crash trying to add an import manually with gopls built using go1.14beta1

[psanford]

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

$ go version
go1.14beta1

Does this issue reproduce with the latest release?

I reproduced this on a gopls build from master.

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/psanford/.cache/go-build"
GOENV="/home/psanford/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/tmp/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/psanford/lib/.go-1.14beta1-ebe68aa4219b673dbd060b8a6d9a339b6b6b0383772aa4349c8183f0a8f339e4"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/psanford/lib/.go-1.14beta1-ebe68aa4219b673dbd060b8a6d9a339b6b6b0383772aa4349c8183f0a8f339e4/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/psanford/projects/thirdparty/gotools/gopls/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-build660370694=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I tried to manually add an import to the import block of the following code (above the "fmt"):

package main

import (
	"fmt"
)

func main() {
	fmt.Println("hello world")
}

After inserting a single non-quote character gopls crashed:

package main

import (
	m
	"fmt"
)

func main() {
	fmt.Println("hello world")
}

The stack trace from gopls:

panic: runtime error: slice bounds out of range [14:0]

goroutine 1797 [running]:
golang.org/x/tools/internal/lsp/source.trimToImports(0xc0002d4540, 0xc0003f7f00, 0xc000226900, 0x50, 0xb7, 0xda4900, 0xc00242ed40, 0x0, 0x0)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/source/format.go:253 +0x505
golang.org/x/tools/internal/lsp/source.computeOneImportFixEdits(0xdb40a0, 0xc00090ce10, 0xdc1a00, 0xc0003c0240, 0xdb42a0, 0xc00242eae0, 0xc002ce85d8, 0xc0022dad00, 0xc002ce8548, 0x45140e, ...)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/source/format.go:151 +0x1cc
golang.org/x/tools/internal/lsp/source.(*completer).importEdits(0xc0020f9a40, 0xc0021d3bf0, 0xc002ce8830, 0x1, 0x1, 0xc0016e17c0, 0xb)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/source/completion_format.go:225 +0x284
golang.org/x/tools/internal/lsp/source.(*completer).item(0xc0020f9a40, 0xdc3be0, 0xc00053cfc0, 0x3fb1eb851eb851ec, 0xc645ff, 0x3, 0x0, 0xc0021d3bf0, 0x0, 0x0, ...)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/source/completion_format.go:119 +0xf93
golang.org/x/tools/internal/lsp/source.(*completer).found(0xc0020f9a40, 0xdc3be0, 0xc00053cfc0, 0x3fb1eb851eb851ec, 0xc645ff, 0x3, 0x0, 0xc0021d3bf0)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/source/completion.go:351 +0x2bc
golang.org/x/tools/internal/lsp/source.(*completer).lexical.func1(0xc645f9, 0x9, 0x0, 0x0, 0xc645ff, 0x3, 0x0, 0x7)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/source/completion.go:903 +0x2ef
golang.org/x/tools/internal/imports.getAllCandidates.func3(0xc002072580, 0xc002072580)
	/home/psanford/projects/thirdparty/gotools/internal/imports/fix.go:688 +0x120
golang.org/x/tools/internal/imports.getCandidatePkgs(0xdb4060, 0xc00053cde0, 0xc002545520, 0xc002560187, 0x28, 0xc001a50b4c, 0x4, 0xc002754460, 0x203000, 0xc0001b7b80)
	/home/psanford/projects/thirdparty/gotools/internal/imports/fix.go:607 +0x30c
golang.org/x/tools/internal/imports.getAllCandidates(0xdb4060, 0xc00053cde0, 0xc0021d3b00, 0x126c365, 0x1, 0xc002560187, 0x28, 0xc001a50b4c, 0x4, 0xc002754460, ...)
	/home/psanford/projects/thirdparty/gotools/internal/imports/fix.go:700 +0x16b
golang.org/x/tools/internal/imports.GetAllCandidates(0xdb4060, 0xc00053cde0, 0xc0021d3b00, 0x126c365, 0x1, 0xc002560187, 0x28, 0xc001a50b4c, 0x4, 0xc002545500, ...)
	/home/psanford/projects/thirdparty/gotools/internal/imports/imports.go:126 +0x106
golang.org/x/tools/internal/lsp/source.(*completer).lexical.func2(0xc002545500, 0xc002545500, 0xc00053cde0)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/source/completion.go:925 +0xf4
golang.org/x/tools/internal/lsp/cache.(*view).RunProcessEnvFunc(0xc0003c0240, 0xdb4060, 0xc00053cde0, 0xc002072080, 0x0, 0x0)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/cache/view.go:307 +0xf3
golang.org/x/tools/internal/lsp/source.(*completer).lexical(0xc0020f9a40, 0x0, 0x0)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/source/completion.go:924 +0xc70
golang.org/x/tools/internal/lsp/source.Completion(0xdb40a0, 0xc00090ce10, 0xdc0d00, 0xc000690500, 0xdb27a0, 0xc0015fa600, 0x4008000000000000, 0x4000000000000000, 0x0, 0x0, ...)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/source/completion.go:530 +0xcad
golang.org/x/tools/internal/lsp.(*Server).completion(0xc00028fce0, 0xdb40a0, 0xc00205e690, 0xc000519920, 0x0, 0x0, 0xc001252fd0)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/completion.go:35 +0x7be
golang.org/x/tools/internal/lsp.(*Server).Completion(0xc00028fce0, 0xdb40a0, 0xc00205e690, 0xc000519920, 0xc000519920, 0x0, 0x0)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/server.go:179 +0x49
golang.org/x/tools/internal/lsp/protocol.serverHandler.Deliver(0xdca9a0, 0xc00028fce0, 0xdb40a0, 0xc00205e690, 0xc0022e4780, 0xc00205e600, 0xc0025aefa0)
	/home/psanford/projects/thirdparty/gotools/internal/lsp/protocol/tsserver.go:316 +0x2596
golang.org/x/tools/internal/jsonrpc2.(*Conn).Run.func1(0xc001cfafc0, 0xc0022e4780, 0xc0002cd9e0, 0xdb40a0, 0xc00205e690, 0x0, 0x0, 0xc001ebd140)
	/home/psanford/projects/thirdparty/gotools/internal/jsonrpc2/jsonrpc2.go:370 +0x160
created by golang.org/x/tools/internal/jsonrpc2.(*Conn).Run
	/home/psanford/projects/thirdparty/gotools/internal/jsonrpc2/jsonrpc2.go:354 +0x874

Process gopls stderr<1> finished

I think this started happening after switching to go1.14.beta1 and rebuilding gopls.

cc: @heschik

[gopherbot]

Thank you for filing a gopls issue! Please take a look at the Troubleshooting guide, and make sure that you have provided all of the relevant information here.

[gopherbot]

Change https://golang.org/cl/215119 mentions this issue: internal/lsp/source: trim file very carefully