Add std logging compatibility and interception options (#44)

http_logging.go

@@ -17,6 +17,7 @@ package log
 import (
 	"crypto/tls"
 	"fmt"
+	"log"
 	"net/http"
 	"strings"
 )
@@ -72,3 +73,28 @@ func LogRequest(r *http.Request, msg string, extraAttributes ...KeyVal) {
 	}
 	S(Info, msg, attr...)
 }
+
+type logWriter struct {
+	source string
+	level  Level
+}
+
+// Returns a Std logger that will log to the given level with the given source attribute.
+// Can be passed for instance to net/http/httputil.ReverseProxy.ErrorLog.
+func NewStdLogger(source string, level Level) *log.Logger {
+	return log.New(logWriter{source, level}, "", 0)
+}
+
+func (w logWriter) Write(p []byte) (n int, err error) {
+	// Force JSON to avoid infinite loop and also skip file/line so it doesn't show this file as the source
+	// (TODO consider passing the level up the stack to look for the caller)
+	s(w.level, false, true, strings.TrimSpace(string(p)), Str("src", w.source))
+	return len(p), nil
+}
+
+// InterceptStandardLogger changes the output of the standard logger to use ours, at the given
+// level, with the source "std", as a catchall.
+func InterceptStandardLogger(level Level) {
+	log.SetFlags(0)
+	log.SetOutput(logWriter{"std", level})
+}

http_logging_test.go

@@ -6,6 +6,7 @@ import (
 	"crypto/tls"
 	"crypto/x509"
 	"crypto/x509/pkix"
+	"log"
 	"net/http"
 	"testing"
 )
@@ -70,3 +71,39 @@ func TestTLSInfo(t *testing.T) {
 		t.Errorf("unexpected for no tls:\n%s\nvs:\n%s\n", got, expected)
 	}
 }
+
+func TestInterceptStandardLogger(t *testing.T) {
+	SetLogLevel(Warning)
+	Config.LogFileAndLine = true
+	Config.JSON = false // check that despite this, it'll be json anyway (so it doesn't go infinite loop)
+	Config.NoTimestamp = true
+	var b bytes.Buffer
+	w := bufio.NewWriter(&b)
+	SetOutput(w)
+	InterceptStandardLogger(Warning)
+	log.Printf("\n\na test\n\n")
+	w.Flush()
+	actual := b.String()
+	expected := `{"level":"warn","msg":"a test","src":"std"}` + "\n"
+	if actual != expected {
+		t.Errorf("unexpected:\n%s\nvs:\n%s\n", actual, expected)
+	}
+}
+
+func TestNewStdLogger(t *testing.T) {
+	SetLogLevel(Info)
+	Config.LogFileAndLine = true
+	Config.JSON = false
+	Config.NoTimestamp = true
+	var b bytes.Buffer
+	w := bufio.NewWriter(&b)
+	SetOutput(w)
+	logger := NewStdLogger("test src", Info)
+	logger.Printf("\n\nanother test\n\n")
+	w.Flush()
+	actual := b.String()
+	expected := `{"level":"info","msg":"another test","src":"test src"}` + "\n"
+	if actual != expected {
+		t.Errorf("unexpected:\n%s\nvs:\n%s\n", actual, expected)
+	}
+}

logger.go

@@ -532,17 +532,18 @@ func Attr[T ValueTypes](key string, value T) KeyVal {
 
 // S logs a message of the given level with additional attributes.
 func S(lvl Level, msg string, attrs ...KeyVal) {
+	s(lvl, Config.LogFileAndLine, Config.JSON, msg, attrs...)
+}
+
+func s(lvl Level, logFileAndLine bool, json bool, msg string, attrs ...KeyVal) {
 	if !Log(lvl) {
 		return
 	}
-	// extra := ""
-	// if Config.GoroutineID {
-	// }
 	buf := strings.Builder{}
 	var format string
 	if Color {
 		format = Colors.Reset + ", " + Colors.Blue + "%s" + Colors.Reset + "=" + LevelToColor[lvl] + "%q"
-	} else if Config.JSON {
+	} else if json {
 		format = ",%q:%q"
 	} else {
 		format = ", %s=%q"
@@ -561,14 +562,14 @@ func S(lvl Level, msg string, attrs ...KeyVal) {
 	} else {
 		lvl1Char = "[" + LevelToStrA[lvl][0:1] + "]"
 	}
-	if Config.LogFileAndLine { //nolint:nestif
-		_, file, line, _ := runtime.Caller(1)
+	if logFileAndLine { //nolint:nestif
+		_, file, line, _ := runtime.Caller(2)
 		file = file[strings.LastIndex(file, "/")+1:]
 		if Color {
 			jsonWrite(fmt.Sprintf("%s%s%s %s:%d%s%s%s%s%s\n",
 				colorTimestamp(), colorGID(), ColorLevelToStr(lvl),
 				file, line, prefix, LevelToColor[lvl], msg, buf.String(), Colors.Reset))
-		} else if Config.JSON {
+		} else if json {
 			jsonWrite(fmt.Sprintf("{%s\"level\":%s,%s\"file\":%q,\"line\":%d,\"msg\":%q%s}\n",
 				jsonTimestamp(), LevelToJSON[lvl], jsonGID(), file, line, msg, buf.String()))
 		} else {
@@ -578,7 +579,7 @@ func S(lvl Level, msg string, attrs ...KeyVal) {
 		if Color {
 			jsonWrite(fmt.Sprintf("%s%s%s%s%s%s%s%s\n",
 				colorTimestamp(), colorGID(), ColorLevelToStr(lvl), prefix, LevelToColor[lvl], msg, buf.String(), Colors.Reset))
-		} else if Config.JSON {
+		} else if json {
 			jsonWrite(fmt.Sprintf("{%s\"level\":%s,\"msg\":%q%s}\n",
 				jsonTimestamp(), LevelToJSON[lvl], msg, buf.String()))
 		} else {