internal/lsp: make sure CodeAction.Command is a pointer

This is causing the "command '' not found" errors that we've been
seeing, specifically reported in microsoft/vscode-go#2920.

Also, fixed an issue with import organization in single-line files that
was caught as a result of this.

Change-Id: I2dfedb5d1b8dda976f356b0d6fcd146e53f1a650
Reviewed-on: https://go-review.googlesource.com/c/tools/+/209219
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/lsp/cmd/capabilities_test.go

@@ -79,12 +79,28 @@ func TestCapabilities(t *testing.T) {
 		ContentChanges: []protocol.TextDocumentContentChangeEvent{
 			{
 				Range: nil,
-				Text:  `package main; func main() {}; func main2() {};`,
+				Text:  `package main; func main() { fmt.Println("") }`,
 			},
 		},
 	}); err != nil {
 		t.Fatal(err)
 	}
+
+	// Send a code action request to validate expected types.
+	actions, err := c.Server.CodeAction(ctx, &protocol.CodeActionParams{
+		TextDocument: protocol.TextDocumentIdentifier{
+			URI: uri,
+		},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, action := range actions {
+		// Validate that an empty command is sent along with import organization responses.
+		if action.Kind == protocol.SourceOrganizeImports && action.Command != nil {
+			t.Errorf("unexpected command for import organization")
+		}
+	}
 }
 
 func validateCapabilities(result *protocol.InitializeResult) error {

internal/lsp/code_action.go

@@ -62,7 +62,7 @@ func (s *Server) codeAction(ctx context.Context, params *protocol.CodeActionPara
 		codeActions = append(codeActions, protocol.CodeAction{
 			Title: "Tidy",
 			Kind:  protocol.SourceOrganizeImports,
-			Command: protocol.Command{
+			Command: &protocol.Command{
 				Title:   "Tidy",
 				Command: "tidy",
 				Arguments: []interface{}{

internal/lsp/protocol/tsprotocol.go

@@ -126,7 +126,7 @@ type CodeAction struct {
 	 * provides a edit and a command, first the edit is
 	 * executed and then the command.
 	 */
-	Command Command `json:"command,omitempty"`
+	Command *Command `json:"command,omitempty"`
 }
 
 /**

internal/lsp/source/format.go

@@ -315,7 +315,9 @@ func trimToFirstNonImport(fset *token.FileSet, f *ast.File, src []byte, err erro
 	}
 	end := f.End()
 	if firstDecl != nil {
-		end = tok.LineStart(fset.Position(firstDecl.Pos()).Line - 1)
+		if firstDeclLine := fset.Position(firstDecl.Pos()).Line; firstDeclLine > 1 {
+			end = tok.LineStart(firstDeclLine - 1)
+		}
 	}
 	// Any errors in the file must be after the part of the file that we care about.
 	switch err := err.(type) {