x/tools/gopls: crash - index out of range

[bmhatfield]

I believe this crash is highly related to #35455. In my local testing, I had demonstrated the new version did not crash, but after updating to master and installing, I am still experiencing an index out of range crash in the same rough area.

I triple checked that I was in fact running the new, fixed version, including by opening /Users/bhatfield/go/src/github.com/golang/tools/internal/lsp/cache/session.go and confirming that the fix was in fact in the code path.

I'm not sure why this did not experimentally reproduce for me during the discussion with @matloob on #35455 , but it is consistently reproducing again now from master.

Included is the gopls output:

Go info
-------
go version go1.13.4 darwin/amd64

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/bhatfield/Library/Caches/go-build"
GOENV="/Users/bhatfield/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/bhatfield/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.13.4/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.13.4/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/w_/sj20ml6511v9vvzd4lzxhvlc0000gn/T/go-build756646728=/tmp/go-build -gno-record-gcc-switches -fno-common"

2019/11/08 15:17:49 : no metadata for file:///Users/bhatfield/Documents/digits/schema
panic: runtime error: index out of range [0] with length 0

goroutine 23 [running]:
golang.org/x/tools/internal/lsp/cache.(*session).bestView(0xc000196420, 0xc0002a8100, 0x78, 0x0, 0x0)
	/Users/bhatfield/go/src/github.com/golang/tools/internal/lsp/cache/session.go:218 +0x18f
golang.org/x/tools/internal/lsp/cache.(*session).DidOpen(0xc000196420, 0x1833900, 0xc0001df1d0, 0xc0002a8100, 0x78, 0x0, 0xc000379000, 0xeb6, 0x1000, 0x1601fe0, ...)
	/Users/bhatfield/go/src/github.com/golang/tools/internal/lsp/cache/session.go:255 +0x2b8
golang.org/x/tools/internal/lsp.(*Server).didOpen(0xc00013db60, 0x1833900, 0xc0001df1d0, 0xc000213000, 0x0, 0xc000240420)
	/Users/bhatfield/go/src/github.com/golang/tools/internal/lsp/text_synchronization.go:29 +0x15e
golang.org/x/tools/internal/lsp.(*Server).DidOpen(0xc00013db60, 0x1833900, 0xc0001df1d0, 0xc000213000, 0xc000213000, 0x0)
	/Users/bhatfield/go/src/github.com/golang/tools/internal/lsp/server.go:135 +0x49
golang.org/x/tools/internal/lsp/protocol.serverHandler.Deliver(0x1848600, 0xc00013db60, 0x1833900, 0xc0001df1d0, 0xc0002a2000, 0xc0001df100, 0xc0001981e0)
	/Users/bhatfield/go/src/github.com/golang/tools/internal/lsp/protocol/tsserver.go:111 +0x1b66
golang.org/x/tools/internal/jsonrpc2.(*Conn).Run.func1(0xc0001a0360, 0xc0002a2000, 0xc00013dbc0, 0x1833900, 0xc0001df1d0, 0x0, 0x0, 0xc00016cce0)
	/Users/bhatfield/go/src/github.com/golang/tools/internal/jsonrpc2/jsonrpc2.go:370 +0x170
created by golang.org/x/tools/internal/jsonrpc2.(*Conn).Run
	/Users/bhatfield/go/src/github.com/golang/tools/internal/jsonrpc2/jsonrpc2.go:354 +0x877
[Error - 3:17:49 PM] 2019/11/08 15:17:49 : no metadata for file:///Users/bhatfield/Documents/digits/schema
[Error - 3:17:49 PM] Connection to server got closed. Server will not be restarted.

@matloob I can confirm just like in #35455 that the "schema" referenced here does not have go modules in it.

[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.

[muirdm]

I'm seeing this too when creating an overlay file in an empty directory (i.e. no go.mod).

[gopherbot]

Change https://golang.org/cl/206497 mentions this issue: internal/lsp/cache: have NewView create view even if load all packages fails