Improve stderr logginf for PostCSS and simlilar

Fixes gohugoio#7584

common/loggers/loggers.go

@@ -39,6 +39,23 @@ func init() {
 	jww.SetLogListeners(jww.LogCounter(GlobalErrorCounter, jww.LevelError))
 }
 
+func LoggerToWriterWithPrefix(logger *log.Logger, prefix string) io.Writer {
+	return prefixWriter{
+		logger: logger,
+		prefix: prefix,
+	}
+}
+
+type prefixWriter struct {
+	logger *log.Logger
+	prefix string
+}
+
+func (w prefixWriter) Write(p []byte) (n int, err error) {
+	w.logger.Printf("%s: %s", w.prefix, p)
+	return len(p), nil
+}
+
 // Logger wraps a *loggers.Logger and some other related logging state.
 type Logger struct {
 	*jww.Notepad

common/loggers/loggers_test.go

@@ -14,6 +14,9 @@
 package loggers
 
 import (
+	"bytes"
+	"fmt"
+	"log"
 	"testing"
 
 	qt "github.com/frankban/quicktest"
@@ -30,3 +33,17 @@ func TestLogger(t *testing.T) {
 	c.Assert(l.ErrorCounter.Count(), qt.Equals, uint64(2))
 
 }
+
+func TestLoggerToWriterWithPrefix(t *testing.T) {
+	c := qt.New(t)
+
+	var b bytes.Buffer
+
+	logger := log.New(&b, "", 0)
+
+	w := LoggerToWriterWithPrefix(logger, "myprefix")
+
+	fmt.Fprint(w, "Hello Hugo!")
+
+	c.Assert(b.String(), qt.Equals, "myprefix: Hello Hugo!\n")
+}

modules/client.go

@@ -531,8 +531,6 @@ func (c *Client) runGo(
 		return nil
 	}
 
-	//defer c.logger.PrintTimer(time.Now(), fmt.Sprint(args))
-
 	stderr := new(bytes.Buffer)
 	cmd := exec.CommandContext(ctx, "go", args...)
 

resources/resource_transformers/babel/babel.go

@@ -15,11 +15,12 @@ package babel
 
 import (
 	"io"
-	"os"
 	"os/exec"
 	"path/filepath"
 	"strconv"
 
+	"github.com/gohugoio/hugo/common/loggers"
+
 	"github.com/gohugoio/hugo/common/hugo"
 	"github.com/gohugoio/hugo/resources/internal"
 
@@ -157,7 +158,7 @@ func (t *babelTransformation) Transform(ctx *resources.ResourceTransformationCtx
 	cmd := exec.Command(binary, cmdArgs...)
 
 	cmd.Stdout = ctx.To
-	cmd.Stderr = os.Stderr
+	cmd.Stderr = loggers.LoggerToWriterWithPrefix(logger.INFO, "babel")
 	cmd.Env = hugo.GetExecEnviron(t.rs.Cfg)
 
 	stdin, err := cmd.StdinPipe()

resources/resource_transformers/postcss/postcss.go

@@ -36,7 +36,6 @@ import (
 	"github.com/gohugoio/hugo/hugofs"
 	"github.com/pkg/errors"
 
-	"os"
 	"os/exec"
 
 	"github.com/mitchellh/mapstructure"
@@ -199,9 +198,10 @@ func (t *postcssTransformation) Transform(ctx *resources.ResourceTransformationC
 	cmd := exec.Command(binary, cmdArgs...)
 
 	var errBuf bytes.Buffer
+	infoW := loggers.LoggerToWriterWithPrefix(logger.INFO, "postcss")
 
 	cmd.Stdout = ctx.To
-	cmd.Stderr = io.MultiWriter(os.Stderr, &errBuf)
+	cmd.Stderr = io.MultiWriter(infoW, &errBuf)
 	cmd.Env = hugo.GetExecEnviron(t.rs.Cfg)
 
 	stdin, err := cmd.StdinPipe()