1 files changed, 82 insertions, 0 deletions
diff --git a/gopls/internal/lsp/cmd/highlight.go b/gopls/internal/lsp/cmd/highlight.go
new file mode 100644
index 000000000..60c04b2d4
--- /dev/null
+++ b/gopls/internal/lsp/cmd/highlight.go
@@ -0,0 +1,82 @@
+// Copyright 2019 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 cmd
+
+import (
+	"context"
+	"flag"
+	"fmt"
+
+	"golang.org/x/tools/gopls/internal/lsp/protocol"
+	"golang.org/x/tools/gopls/internal/span"
+	"golang.org/x/tools/internal/tool"
+)
+
+// highlight implements the highlight verb for gopls.
+type highlight struct {
+	app *Application
+}
+
+func (r *highlight) Name() string      { return "highlight" }
+func (r *highlight) Parent() string    { return r.app.Name() }
+func (r *highlight) Usage() string     { return "<position>" }
+func (r *highlight) ShortHelp() string { return "display selected identifier's highlights" }
+func (r *highlight) DetailedHelp(f *flag.FlagSet) {
+	fmt.Fprint(f.Output(), `
+Example:
+
+	$ # 1-indexed location (:line:column or :#offset) of the target identifier
+	$ gopls highlight helper/helper.go:8:6
+	$ gopls highlight helper/helper.go:#53
+`)
+	printFlagDefaults(f)
+}
+
+func (r *highlight) Run(ctx context.Context, args ...string) error {
+	if len(args) != 1 {
+		return tool.CommandLineErrorf("highlight expects 1 argument (position)")
+	}
+
+	conn, err := r.app.connect(ctx)
+	if err != nil {
+		return err
+	}
+	defer conn.terminate(ctx)
+
+	from := span.Parse(args[0])
+	file := conn.openFile(ctx, from.URI())
+	if file.err != nil {
+		return file.err
+	}
+
+	loc, err := file.mapper.SpanLocation(from)
+	if err != nil {
+		return err
+	}
+
+	p := protocol.DocumentHighlightParams{
+		TextDocumentPositionParams: protocol.LocationTextDocumentPositionParams(loc),
+	}
+	highlights, err := conn.DocumentHighlight(ctx, &p)
+	if err != nil {
+		return err
+	}
+
+	var results []span.Span
+	for _, h := range highlights {
+		s, err := file.mapper.RangeSpan(h.Range)
+		if err != nil {
+			return err
+		}
+		results = append(results, s)
+	}
+	// Sort results to make tests deterministic since DocumentHighlight uses a map.
+	span.SortSpans(results)
+
+	for _, s := range results {
+		fmt.Println(s)
+	}
+	return nil
+}