x/tools/gopls: omit empty JSON-RPC error data

[uhthomas]

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

$ go version
go version go1.14.4 darwin/amd64

Does this issue reproduce with the latest release?

Yes.

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/thomas/Library/Caches/go-build"
GOENV="/Users/thomas/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GONOPROXY="code.cfops.it"
GONOSUMDB="code.cfops.it"
GOOS="darwin"
GOPATH="/Users/thomas/go"
GOPRIVATE="code.cfops.it"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/Cellar/go/1.14.4/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.14.4/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/thomas/cloudflare/segments/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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/d5/hqd0d3f17h7gmntg94k251z80000gn/T/go-build278475873=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

JSON-RPC errors always encode data as null. The spec states it may be omitted.

What did you expect to see?

JSON-RPC errors should not encode data if empty.

{
	"code": 0,
	"message": ""
}

What did you see instead?

{
	"code": 0,
	"message": "",
	"data": null
}

[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/239059 mentions this issue: internal/jsonrpc2: Omit empty error data