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

$ go version
go version devel +da4d58587e Sat Dec 7 15:57:30 2019 +0000 linux/amd64
$ go list -m golang.org/x/tools
golang.org/x/tools v0.0.0-20191113223546-95cb2a1a7eae => github.com/myitcvforks/tools v0.0.0-20191207011554-b8ce9b8c6b5a
$ go list -m golang.org/x/tools/gopls
golang.org/x/tools/gopls v0.1.8-0.20191115202509-3a792d9c32b2 => github.com/myitcvforks/tools/gopls v0.0.0-20191207011554-b8ce9b8c6b5a

Does this issue reproduce with the latest release?

Yes

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

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/myitcv/.cache/go-build"
GOENV="/home/myitcv/.config/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/myitcv/gostuff"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/myitcv/gos"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/myitcv/gos/pkg/tool/linux_amd64"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/myitcv/gostuff/src/github.com/myitcv/govim/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-build628797223=/tmp/go-build -gno-record-gcc-switches"

What did you do?

According to the LSP spec:

https://microsoft.github.io/language-server-protocol/specifications/specification-3-15/#textDocument_didSave

DidSaveTextDocumentParams is defined as:

interface DidSaveTextDocumentParams {
	/**
	 * The document that was saved.
	 */
	textDocument: TextDocumentIdentifier;

	/**
	 * Optional the content when saved. Depends on the includeText value
	 * when the save notification was requested.
	 */
	text?: string;
}

Note the text field is optional.

However the type as generated for gopls is as follows:

type DidSaveTextDocumentParams struct {
	/**
	 * The document that was closed.
	 */
	TextDocument VersionedTextDocumentIdentifier `json:"textDocument"`
	/**
	 * Optional the content when saved. Depends on the includeText value
	 * when the save notification was requested.
	 */
	Text string `json:"text,omitempty"`
}

i.e. Text is a string type when I think it should be a *string type.

Hence it's impossible to distinguish between "a file of zero length" and "no file contents being sent."

What did you expect to see?

Per above

What did you see instead?

Per above

cc @stamblerre @pjweinb