Update for review comments

Author: rneatherway

gopls/internal/lsp/cmd/test/cmdtest.go

@@ -118,9 +118,7 @@ func (r *runner) InlayHints(t *testing.T, spn span.Span) {
 	// TODO: inlayHints not supported on command line
 }
 
-func (r *runner) SelectionRanges(t *testing.T, spn span.Span) {
-	// TODO: selectionRanges not supported on command line
-}
+func (r *runner) SelectionRanges(t *testing.T, spn span.Span) {}
 
 func (r *runner) runGoplsCmd(t testing.TB, args ...string) (string, string) {
 	rStdout, wStdout, err := os.Pipe()

gopls/internal/lsp/lsp_test.go

@@ -1307,19 +1307,19 @@ func (r *runner) SelectionRanges(t *testing.T, spn span.Span) {
 		Positions: []protocol.Position{loc.Range.Start},
 	})
 	if err != nil {
-		t.Error(err)
+		t.Fatal(err)
 	}
 
 	sb := &strings.Builder{}
 	for i, path := range ranges {
 		fmt.Fprintf(sb, "Ranges %d: ", i)
-		r := path
+		rng := path
 		for {
-			s, err := sm.Offset(r.Range.Start)
+			s, err := sm.Offset(rng.Range.Start)
 			if err != nil {
 				t.Error(err)
 			}
-			e, err := sm.Offset(r.Range.End)
+			e, err := sm.Offset(rng.Range.End)
 			if err != nil {
 				t.Error(err)
 			}
@@ -1331,25 +1331,26 @@ func (r *runner) SelectionRanges(t *testing.T, spn span.Span) {
 				snippet = string(sm.Content[s:s+15]) + "..." + string(sm.Content[e-15:e])
 			}
 
-			fmt.Fprintf(sb, "\n\t%v '%s'", r.Range, strings.ReplaceAll(snippet, "\n", "\\n"))
+			fmt.Fprintf(sb, "\n\t%v %q", rng.Range, strings.ReplaceAll(snippet, "\n", "\\n"))
 
-			if r.Parent == nil {
+			if rng.Parent == nil {
 				break
 			}
-			r = *r.Parent
+			rng = *rng.Parent
 		}
 		sb.WriteRune('\n')
 	}
 	got := sb.String()
 
-	want := r.data.Golden(t, "selectionrange_"+tests.SpanName(spn), uri.Filename(), func() ([]byte, error) {
+	testName := "selectionrange_" + tests.SpanName(spn)
+	want := r.data.Golden(t, testName, uri.Filename(), func() ([]byte, error) {
 		return []byte(got), nil
 	})
 	if want == nil {
 		t.Fatalf("golden file %q not found", uri.Filename())
 	}
 	if diff := compare.Text(got, string(want)); diff != "" {
-		t.Errorf("%s mismatch\n%s", command.AddImport, diff)
+		t.Errorf("%s mismatch\n%s", testName, diff)
 	}
 }
 

gopls/internal/lsp/selection_range.go

@@ -1,3 +1,7 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
 package lsp
 
 import (
@@ -9,6 +13,17 @@ import (
 	"golang.org/x/tools/internal/event"
 )
 
+// selectionRange defines the textDocument/selectionRange feature,
+// which, given a list of positions within a file,
+// reports a linked list of enclosing syntactic blocks, innermost first.
+//
+// See https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_selectionRange.
+//
+// This feature can be used by a client to implement "expand selection" in a
+// language-aware fashion. Multiple input positions are supported to allow
+// for multiple cursors, and the entire path up to the whole document is
+// returned for each cursor to avoid multiple round-trips when the user is
+// likely to issue this command multiple times in quick succession.
 func (s *Server) selectionRange(ctx context.Context, params *protocol.SelectionRangeParams) ([]protocol.SelectionRange, error) {
 	ctx, done := event.Start(ctx, "lsp.Server.documentSymbol")
 	defer done()
@@ -33,21 +48,20 @@ func (s *Server) selectionRange(ctx context.Context, params *protocol.SelectionR
 
 		path, _ := astutil.PathEnclosingInterval(pgf.File, pos, pos)
 
-		current := &result[i]
+		tail := &result[i] // tail of the Parent linked list, built head first
 
 		for j, node := range path {
 			rng, err := pgf.Mapper.PosRange(node.Pos(), node.End())
 			if err != nil {
 				return nil, err
 			}
 
-			// Option 2
-			current.Range = rng
-
-			if j < len(path)-1 {
-				current.Parent = &protocol.SelectionRange{}
-				current = current.Parent
+			// Add node to tail.
+			if j > 0 {
+				tail.Parent = &protocol.SelectionRange{}
+				tail = tail.Parent
 			}
+			tail.Range = rng
 		}
 	}