tools/gopls: add cmd support for highlight

This change adds command line support for highlight.
Provided with an identifier position, it will display
the list of highlights for that within the same file.

Example:

$ gopls highlight ~/tmp/foo/main.go:3:9
$
$ 3:9-6:0
$ 10:22-11:32
$ 12:10-12:9
$ 12:20-30:0

Updates golang/go#32875

Change-Id: I5de73d9fbd9bcc59a3f62e7e9a1331bc3866bc75
Reviewed-on: https://go-review.googlesource.com/c/tools/+/207291
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/cmd/cmd.go

@@ -144,9 +144,10 @@ func (app *Application) commands() []tool.Application {
 		&check{app: app},
 		&foldingRanges{app: app},
 		&format{app: app},
-		&links{app: app},
+		&highlight{app: app},
 		&implementation{app: app},
 		&imports{app: app},
+		&links{app: app},
 		&query{app: app},
 		&references{app: app},
 		&rename{app: app},

internal/lsp/cmd/highlight.go

@@ -0,0 +1,81 @@
+// 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/internal/lsp/protocol"
+	"golang.org/x/tools/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) 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
+
+  gopls highlight flags are:
+`)
+	f.PrintDefaults()
+}
+
+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.AddFile(ctx, from.URI())
+	if file.err != nil {
+		return file.err
+	}
+
+	loc, err := file.mapper.Location(from)
+	if err != nil {
+		return err
+	}
+
+	p := protocol.DocumentHighlightParams{
+		TextDocumentPositionParams: protocol.TextDocumentPositionParams{
+			TextDocument: protocol.TextDocumentIdentifier{URI: loc.URI},
+			Position:     loc.Range.Start,
+		},
+	}
+	highlights, err := conn.DocumentHighlight(ctx, &p)
+	if err != nil {
+		return err
+	}
+
+	for _, h := range highlights {
+		l := protocol.Location{Range: h.Range}
+		s, err := file.mapper.Span(l)
+		if err != nil {
+			return err
+		}
+		fmt.Println(s)
+	}
+
+	return nil
+}

internal/lsp/cmd/test/cmdtest.go

@@ -95,10 +95,6 @@ func (r *runner) RankCompletion(t *testing.T, src span.Span, test tests.Completi
 	//TODO: add command line completions tests when it works
 }
 
-func (r *runner) Highlight(t *testing.T, src span.Span, locations []span.Span) {
-	//TODO: add command line highlight tests when it works
-}
-
 func (r *runner) PrepareRename(t *testing.T, src span.Span, want *source.PrepareItem) {
 	//TODO: add command line prepare rename tests when it works
 }

internal/lsp/cmd/test/highlight.go

@@ -0,0 +1,25 @@
+package cmdtest
+
+import (
+	"testing"
+
+	"fmt"
+
+	"golang.org/x/tools/internal/span"
+)
+
+func (r *runner) Highlight(t *testing.T, spn span.Span, spans []span.Span) {
+	var expect string
+	for _, l := range spans {
+		expect += fmt.Sprintln(l)
+	}
+	expect = r.Normalize(expect)
+
+	uri := spn.URI()
+	filename := uri.Filename()
+	target := filename + ":" + fmt.Sprint(spn.Start().Line()) + ":" + fmt.Sprint(spn.Start().Column())
+	got, _ := r.NormalizeGoplsCmd(t, "highlight", target)
+	if expect != got {
+		t.Errorf("highlight failed for %s expected:\n%s\ngot:\n%s", target, expect, got)
+	}
+}