internal/lsp: make Text in DidSave request a pointer

Fixes golang/go#36063

Change-Id: I223ead138111239ae1894f5565414ac384c016e2
Reviewed-on: https://go-review.googlesource.com/c/tools/+/210780
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Peter Weinberger <pjw@google.com>

internal/lsp/cmd/capabilities_test.go

@@ -101,6 +101,19 @@ func TestCapabilities(t *testing.T) {
 			t.Errorf("unexpected command for import organization")
 		}
 	}
+
+	if err := c.Server.DidSave(ctx, &protocol.DidSaveTextDocumentParams{
+		TextDocument: protocol.VersionedTextDocumentIdentifier{
+			Version: 2,
+			TextDocumentIdentifier: protocol.TextDocumentIdentifier{
+				URI: uri,
+			},
+		},
+		// LSP specifies that a file can be saved with optional text, so this field must be nil.
+		Text: nil,
+	}); err != nil {
+		t.Fatal(err)
+	}
 }
 
 func validateCapabilities(result *protocol.InitializeResult) error {

internal/lsp/protocol/tsprotocol.go

@@ -1027,7 +1027,7 @@ type DidSaveTextDocumentParams struct {
 	 * Optional the content when saved. Depends on the includeText value
 	 * when the save notification was requested.
 	 */
-	Text string `json:"text,omitempty"`
+	Text *string `json:"text,omitempty"`
 }
 
 type DocumentColorClientCapabilities struct {

internal/lsp/text_synchronization.go

@@ -30,12 +30,15 @@ func (s *Server) didOpen(ctx context.Context, params *protocol.DidOpenTextDocume
 }
 
 func (s *Server) didSave(ctx context.Context, params *protocol.DidSaveTextDocumentParams) error {
-	return s.didModifyFile(ctx, source.FileModification{
+	c := source.FileModification{
 		URI:     span.NewURI(params.TextDocument.URI),
 		Action:  source.Save,
 		Version: params.TextDocument.Version,
-		Text:    []byte(params.Text),
-	})
+	}
+	if params.Text != nil {
+		c.Text = []byte(*params.Text)
+	}
+	return s.didModifyFile(ctx, c)
 }
 
 func (s *Server) didClose(ctx context.Context, params *protocol.DidCloseTextDocumentParams) error {