Make level configurable for NewStdLog. (uber-go#439) (uber-go#487)

With this change new function is added called NewStdLogAt. It has same
behaviour as NewStdLog, but it allows providing log level to use by
returned *log.Logger.

global.go

@@ -22,14 +22,17 @@ package zap
 
 import (
 	"bytes"
+	"fmt"
 	"log"
 	"os"
 	"sync"
+
+	"go.uber.org/zap/zapcore"
 )
 
 const (
 	_stdLogDefaultDepth = 2
-	_loggerWriterDepth  = 1
+	_loggerWriterDepth  = 2
 )
 
 var (
@@ -71,9 +74,35 @@ func ReplaceGlobals(logger *Logger) func() {
 // InfoLevel. To redirect the standard library's package-global logging
 // functions, use RedirectStdLog instead.
 func NewStdLog(l *Logger) *log.Logger {
-	return log.New(&loggerWriter{l.WithOptions(
-		AddCallerSkip(_stdLogDefaultDepth + _loggerWriterDepth),
-	)}, "" /* prefix */, 0 /* flags */)
+	logger := l.WithOptions(AddCallerSkip(_stdLogDefaultDepth + _loggerWriterDepth))
+	f := logger.Info
+	return log.New(&loggerWriter{f}, "" /* prefix */, 0 /* flags */)
+}
+
+// NewStdLogAt returns *log.Logger which writes to supplied zap logger at
+// required level.
+func NewStdLogAt(l *Logger, level zapcore.Level) (*log.Logger, error) {
+	logger := l.WithOptions(AddCallerSkip(_stdLogDefaultDepth + _loggerWriterDepth))
+	var logFunc func(string, ...zapcore.Field)
+	switch level {
+	case DebugLevel:
+		logFunc = logger.Debug
+	case InfoLevel:
+		logFunc = logger.Info
+	case WarnLevel:
+		logFunc = logger.Warn
+	case ErrorLevel:
+		logFunc = logger.Error
+	case DPanicLevel:
+		logFunc = logger.DPanic
+	case PanicLevel:
+		logFunc = logger.Panic
+	case FatalLevel:
+		logFunc = logger.Fatal
+	default:
+		return nil, fmt.Errorf("unrecognized level: %q", level)
+	}
+	return log.New(&loggerWriter{logFunc}, "" /* prefix */, 0 /* flags */), nil
 }
 
 // RedirectStdLog redirects output from the standard library's package-global
@@ -88,9 +117,10 @@ func RedirectStdLog(l *Logger) func() {
 	prefix := log.Prefix()
 	log.SetFlags(0)
 	log.SetPrefix("")
-	log.SetOutput(&loggerWriter{l.WithOptions(
+	logFunc := l.WithOptions(
 		AddCallerSkip(_stdLogDefaultDepth + _loggerWriterDepth),
-	)})
+	).Info
+	log.SetOutput(&loggerWriter{logFunc})
 	return func() {
 		log.SetFlags(flags)
 		log.SetPrefix(prefix)
@@ -99,11 +129,11 @@ func RedirectStdLog(l *Logger) func() {
 }
 
 type loggerWriter struct {
-	logger *Logger
+	logFunc func(msg string, fields ...zapcore.Field)
 }
 
 func (l *loggerWriter) Write(p []byte) (int, error) {
 	p = bytes.TrimSpace(p)
-	l.logger.Info(string(p))
+	l.logFunc(string(p))
 	return len(p), nil
 }

global_test.go

@@ -26,6 +26,8 @@ import (
 	"testing"
 	"time"
 
+	"go.uber.org/zap/internal/exit"
+
 	"go.uber.org/zap/zapcore"
 	"go.uber.org/zap/zaptest"
 	"go.uber.org/zap/zaptest/observer"
@@ -96,20 +98,55 @@ func TestNewStdLog(t *testing.T) {
 	withLogger(t, DebugLevel, []Option{AddCaller()}, func(l *Logger, logs *observer.ObservedLogs) {
 		std := NewStdLog(l)
 		std.Print("redirected")
+		checkStdLogMessage(t, "redirected", logs)
+	})
+}
 
-		require.Equal(t, 1, logs.Len(), "Expected exactly one entry to be logged.")
-		entry := logs.AllUntimed()[0]
-		assert.Equal(t, []zapcore.Field{}, entry.Context, "Unexpected entry context.")
-		assert.Equal(t, "redirected", entry.Entry.Message, "Unexpected entry message.")
-		assert.Regexp(
-			t,
-			`go.uber.org/zap/global_test.go:\d+$`,
-			entry.Entry.Caller.String(),
-			"Unexpected caller annotation.",
-		)
+func TestNewStdLogAt(t *testing.T) {
+	// include DPanicLevel here, but do not include Development in options
+	levels := []zapcore.Level{DebugLevel, InfoLevel, WarnLevel, ErrorLevel, DPanicLevel}
+	for _, level := range levels {
+		withLogger(t, DebugLevel, []Option{AddCaller()}, func(l *Logger, logs *observer.ObservedLogs) {
+			std, err := NewStdLogAt(l, level)
+			require.NoError(t, err, "Unexpected error.")
+			std.Print("redirected")
+			checkStdLogMessage(t, "redirected", logs)
+		})
+	}
+}
+
+func TestNewStdLogAtPanics(t *testing.T) {
+	// include DPanicLevel here and enable Development in options
+	levels := []zapcore.Level{DPanicLevel, PanicLevel}
+	for _, level := range levels {
+		withLogger(t, DebugLevel, []Option{AddCaller(), Development()}, func(l *Logger, logs *observer.ObservedLogs) {
+			std, err := NewStdLogAt(l, level)
+			require.NoError(t, err, "Unexpected error")
+			assert.Panics(t, func() { std.Print("redirected") }, "Expected log to panic.")
+			checkStdLogMessage(t, "redirected", logs)
+		})
+	}
+}
+
+func TestNewStdLogAtFatal(t *testing.T) {
+	withLogger(t, DebugLevel, []Option{AddCaller()}, func(l *Logger, logs *observer.ObservedLogs) {
+		stub := exit.WithStub(func() {
+			std, err := NewStdLogAt(l, FatalLevel)
+			require.NoError(t, err, "Unexpected error.")
+			std.Print("redirected")
+			checkStdLogMessage(t, "redirected", logs)
+		})
+		assert.True(t, true, stub.Exited, "Expected Fatal logger call to terminate process.")
+		stub.Unstub()
 	})
 }
 
+func TestNewStdLogAtInvalid(t *testing.T) {
+	_, err := NewStdLogAt(NewNop(), zapcore.Level(99))
+	assert.Error(t, err, "Expected to get error.")
+	assert.Contains(t, err.Error(), "99", "Expected level code in error message")
+}
+
 func TestRedirectStdLog(t *testing.T) {
 	initialFlags := log.Flags()
 	initialPrefix := log.Prefix()
@@ -137,3 +174,16 @@ func TestRedirectStdLogCaller(t *testing.T) {
 		assert.Contains(t, entries[0].Entry.Caller.File, "global_test.go", "Unexpected caller annotation.")
 	})
 }
+
+func checkStdLogMessage(t *testing.T, msg string, logs *observer.ObservedLogs) {
+	require.Equal(t, 1, logs.Len(), "Expected exactly one entry to be logged")
+	entry := logs.AllUntimed()[0]
+	assert.Equal(t, []zapcore.Field{}, entry.Context, "Unexpected entry context.")
+	assert.Equal(t, "redirected", entry.Entry.Message, "Unexpected entry message.")
+	assert.Regexp(
+		t,
+		`go.uber.org/zap/global_test.go:\d+$`,
+		entry.Entry.Caller.String(),
+		"Unexpected caller annotation.",
+	)
+}