go: x/tools/gopls: format on save breaks imports when reordered

What did you do?

In https://github.com/hortbot/hortbot/blob/master/internal/cli/flags/ircflags/ircargs.go, swap around some import lines and save.

My Go-related configs:

    "go.lintOnSave": "workspace",
    "go.lintTool": "golangci-lint",
    "go.formatTool": "goimports",
    "go.useLanguageServer": true,
    "go.alternateTools": {
        "go-langserver": "gopls"
    },
    "go.buildOnSave": "off",
    "go.vetOnSave": "off",
    "[go]": {
        "editor.snippetSuggestions": "none",
        "editor.formatOnSave": true,
        "editor.codeActionsOnSave": {
            "source.organizeImports": true
        },
        "editor.codeActionsOnSaveTimeout": 3000
    },
    "gopls": {
        "completeUnimported": true,
        "watchFileChanges": true,
        "deepCompletion": true,
        "go-diff": true,
        "local": "github.com/hortbot/hortbot"
    },

Though I’d normally configure local in the project’s settings, since it doesn’t make much sense globally.

What did you expect to see?

The imports are reordered back to the way they were (or re-sorted by the local feature).

What did you see instead?

The imports get formatted very wrong. Imports get deleted, duplicated, and sometimes turn out syntatically correct with misplaced quotes. I tried to do a screencap.

https://streamable.com/ffxjz

I also verified this without go-diff enabled to see if it was the diff algorithm, but there was no difference.

Also, the local option is applied at an unknown time. I want things to behave exactly as they do with VS Code + goimports, i.e. “hit save, imports are reordered and fixed”, but can’t seem to get that to work.

Build info

golang.org/x/tools/gopls master
    golang.org/x/tools/gopls@v0.1.8-0.20191105231337-689d0f08e67a h1:4tnHOn2ZDC1EOp6PyPlUfrxeuw1IzXmJ6Hh359rRlSI=
    github.com/BurntSushi/toml@v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
    github.com/sergi/go-diff@v1.0.0 h1:Kpca3qRNrduNnOQeazBd0ysaKrUJiIuISHxogkT9RPQ=
    golang.org/x/sync@v0.0.0-20190423024810-112230192c58 h1:8gQV6CLnAEikrhgkHFbMAEhagSSnXWGV915qUMm9mrU=
    golang.org/x/tools@v0.0.0-20191105231337-689d0f08e67a h1:RzzIfXstYPS78k0QViPGpDcTlV+QuYrbxVmsxDHdxTs=
    golang.org/x/xerrors@v0.0.0-20190717185122-a985d3407aa7 h1:9zdDQZ7Thm29KFXgAX/+yaf3eVbP7djjWp/dXAppNCc=
    honnef.co/go/tools@v0.0.1-2019.2.3 h1:3JgtbtFHMiCmsznwGVTUWbgGov+pVqnlf1dEJTNAXeM=

Go info

go version go1.13.4 linux/amd64

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/jake/.cache/go-build"
GOENV="/home/jake/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/jake/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/jake/zikaeroh/hortbot/hortbot/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-build676081404=/tmp/go-build -gno-record-gcc-switches"