internal/gopathwalk: use opts.Logf for errors if set

Change-Id: Ic963c179a9fda8f7c5c6220a7e4558cccff374be
Reviewed-on: https://go-review.googlesource.com/c/tools/+/508505
Reviewed-by: Heschi Kreinick <heschi@google.com>
Run-TryBot: Bryan Mills <bcmills@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

internal/gopathwalk/walk.go

@@ -9,7 +9,6 @@ package gopathwalk
 import (
 	"bufio"
 	"bytes"
-	"fmt"
 	"log"
 	"os"
 	"path/filepath"
@@ -77,7 +76,7 @@ func walkDir(root Root, add func(Root, string), skip func(root Root, dir string)
 	}
 	start := time.Now()
 	if opts.Logf != nil {
-		opts.Logf("gopathwalk: scanning %s", root.Path)
+		opts.Logf("scanning %s", root.Path)
 	}
 	w := &walker{
 		root: root,
@@ -87,11 +86,15 @@ func walkDir(root Root, add func(Root, string), skip func(root Root, dir string)
 	}
 	w.init()
 	if err := fastwalk.Walk(root.Path, w.walk); err != nil {
-		log.Printf("gopathwalk: scanning directory %v: %v", root.Path, err)
+		logf := opts.Logf
+		if logf == nil {
+			logf = log.Printf
+		}
+		logf("scanning directory %v: %v", root.Path, err)
 	}
 
 	if opts.Logf != nil {
-		opts.Logf("gopathwalk: scanned %s in %v", root.Path, time.Since(start))
+		opts.Logf("scanned %s in %v", root.Path, time.Since(start))
 	}
 }
 
@@ -221,7 +224,11 @@ func (w *walker) walk(path string, typ os.FileMode) error {
 func (w *walker) shouldTraverse(path string) bool {
 	ts, err := os.Stat(path)
 	if err != nil {
-		fmt.Fprintln(os.Stderr, err)
+		logf := w.opts.Logf
+		if logf == nil {
+			logf = log.Printf
+		}
+		logf("%v", err)
 		return false
 	}
 	if !ts.IsDir() {

internal/imports/mod_test.go

@@ -1292,7 +1292,7 @@ import (
 func BenchmarkScanModCache(b *testing.B) {
 	env := &ProcessEnv{
 		GocmdRunner: &gocommand.Runner{},
-		Logf:        log.Printf,
+		Logf:        b.Logf,
 	}
 	exclude := []gopathwalk.RootType{gopathwalk.RootGOROOT}
 	resolver, err := env.GetResolver()