internal/lsp: add config flag to hide debugging output

Add a new "verboseOutput" config flag (defaults to "false") to enable
verbose go/packages and imports output. Previously this output was
always present.

The go/packages output would dump out the entire (humongous) "go list"
JSON response which would lock up my editor for a second whenever
something triggered a go/packages call.

The imports output would produce a bunch of "gopathwalk" debug
messages that aren't useful in general and in particular add noisy
output to tests.

Change-Id: Ie4693d074cb84f1397e0e51d7346dc9391bd1278
Reviewed-on: https://go-review.googlesource.com/c/tools/+/205138
Reviewed-by: Koichi Shiraishi <zchee.io@gmail.com>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

internal/lsp/cache/view.go

@@ -128,7 +128,9 @@ func (v *view) Config(ctx context.Context) *packages.Config {
 			panic("go/packages must not be used to parse files")
 		},
 		Logf: func(format string, args ...interface{}) {
+			if v.options.VerboseOutput {
 				log.Print(ctx, fmt.Sprintf(format, args...))
+			}
 		},
 		Tests: true,
 	}
@@ -186,7 +188,7 @@ func (v *view) buildProcessEnv(ctx context.Context) (*imports.ProcessEnv, error)
 			log.Print(ctx, fmt.Sprintf(format, args...))
 		},
 		LocalPrefix: v.options.LocalPrefix,
-		Debug:       true,
+		Debug:       v.options.VerboseOutput,
 	}
 	for _, kv := range cfg.Env {
 		split := strings.Split(kv, "=")

internal/lsp/source/options.go

@@ -108,6 +108,8 @@ type Options struct {
 
 	// LocalPrefix is used to specify goimports's -local behavior.
 	LocalPrefix string
+
+	VerboseOutput bool
 }
 
 type CompletionOptions struct {
@@ -289,6 +291,9 @@ func (o *Options) set(name string, value interface{}) OptionResult {
 		}
 		o.LocalPrefix = localPrefix
 
+	case "verboseOutput":
+		result.setBool(&o.VerboseOutput)
+
 	// Deprecated settings.
 	case "wantSuggestedFixes":
 		result.State = OptionDeprecated