From 15caffe3638a9980a86b86f8ccaec8524b4e9fcc Mon Sep 17 00:00:00 2001
From: Dominik Menke <dom@digineo.de>
Date: Mon, 29 Jan 2024 19:58:32 +0100
Subject: [PATCH] refactor: change logger to only accept slog.Attrs

Y'know, for performance. Logging is intense
---
 service/middleware/logging.go |  3 +-
 xlog/discard.go               | 17 ++++++-----
 xlog/{log.go => xlog.go}      | 55 ++++++++++++++++-------------------
 3 files changed, 37 insertions(+), 38 deletions(-)
 rename xlog/{log.go => xlog.go} (64%)

diff --git a/service/middleware/logging.go b/service/middleware/logging.go
index de8e378..160730b 100644
--- a/service/middleware/logging.go
+++ b/service/middleware/logging.go
@@ -1,6 +1,7 @@
 package middleware
 
 import (
+	"log/slog"
 	"net"
 	"net/http"
 
@@ -33,7 +34,7 @@ func WithLogging(log xlog.Logger) func(http.Handler) http.Handler {
 
 			next.ServeHTTP(rl, r)
 
-			logAttrs := []any{ // []slog.Attr
+			logAttrs := []slog.Attr{
 				RequestIDField(r.Context()),
 				xlog.String("method", r.Method),
 				xlog.Int("status", rl.status),
diff --git a/xlog/discard.go b/xlog/discard.go
index 58a674a..814909d 100644
--- a/xlog/discard.go
+++ b/xlog/discard.go
@@ -1,6 +1,9 @@
 package xlog
 
-import "os"
+import (
+	"log/slog"
+	"os"
+)
 
 type discard struct{}
 
@@ -13,9 +16,9 @@ func NewDiscard() Logger {
 	return &discard{}
 }
 
-func (*discard) Debug(msg string, args ...any) {}
-func (*discard) Info(msg string, args ...any)  {}
-func (*discard) Warn(msg string, args ...any)  {}
-func (*discard) Error(msg string, args ...any) {}
-func (*discard) Fatal(msg string, args ...any) { os.Exit(1) }
-func (d *discard) With(args ...any) Logger     { return d }
+func (*discard) Debug(string, ...slog.Attr) {}
+func (*discard) Info(string, ...slog.Attr)  {}
+func (*discard) Warn(string, ...slog.Attr)  {}
+func (*discard) Error(string, ...slog.Attr) {}
+func (*discard) Fatal(string, ...slog.Attr) { os.Exit(1) }
+func (d *discard) With(...slog.Attr) Logger { return d }
diff --git a/xlog/log.go b/xlog/xlog.go
similarity index 64%
rename from xlog/log.go
rename to xlog/xlog.go
index 2bcec84..528d1a9 100644
--- a/xlog/log.go
+++ b/xlog/xlog.go
@@ -13,29 +13,30 @@ import (
 // A Logger allows writing messages with various severities.
 type Logger interface {
 	// Debug writes log messages with DEBUG severity.
-	Debug(msg string, args ...any)
+	Debug(msg string, a ...slog.Attr)
 	// Info writes log messages with INFO severity.
-	Info(msg string, args ...any)
+	Info(msg string, a ...slog.Attr)
 	// Warn writes log messages with WARN severity.
-	Warn(msg string, args ...any)
+	Warn(msg string, a ...slog.Attr)
 	// Error writes log messages with ERROR severity.
-	Error(msg string, args ...any)
+	Error(msg string, a ...slog.Attr)
 	// Fatal writes log messages with ERROR severity, and then
 	// exits the whole program.
-	Fatal(msg string, args ...any)
-	// With creates a child logger, and adds the given arguments
-	// to each child message output
-	With(args ...any) Logger
+	Fatal(msg string, a ...slog.Attr)
+	// With returns a Logger that includes the given attributes
+	// in each output operation.
+	With(a ...slog.Attr) Logger
 }
 
 type logger struct {
 	l *slog.Logger
-	// context holds the arguments received from With().
-	context []any
 }
 
+// New creates a new logger instance. By default, log messages are
+// written to stdout, and the log level is INFO.
 func New(opt ...Option) (Logger, error) {
 	opts := options{
+		output:      os.Stdout,
 		handlerOpts: &slog.HandlerOptions{},
 	}
 
@@ -70,48 +71,42 @@ func New(opt ...Option) (Logger, error) {
 }
 
 // log creates a log record. It is called by Debug, Info, etc.
-func (log *logger) log(level slog.Level, msg string, args ...any) {
+func (log *logger) log(level slog.Level, msg string, a ...slog.Attr) {
 	if !log.l.Enabled(context.Background(), level) {
 		return
 	}
 	var pcs [1]uintptr
 	runtime.Callers(3, pcs[:]) // skip runtime.Callers, log, and our caller
 	r := slog.NewRecord(time.Now(), level, msg, pcs[0])
-	r.Add(log.context...)
-	r.Add(args...)
+	r.AddAttrs(a...)
 	_ = log.l.Handler().Handle(context.Background(), r)
 }
 
-func (log *logger) Debug(msg string, args ...any) {
-	log.log(slog.LevelDebug, msg, args...)
+func (log *logger) Debug(msg string, a ...slog.Attr) {
+	log.log(slog.LevelDebug, msg, a...)
 }
 
-func (log *logger) Info(msg string, args ...any) {
-	log.log(slog.LevelInfo, msg, args...)
+func (log *logger) Info(msg string, a ...slog.Attr) {
+	log.log(slog.LevelInfo, msg, a...)
 }
 
-func (log *logger) Warn(msg string, args ...any) {
-	log.log(slog.LevelWarn, msg, args...)
+func (log *logger) Warn(msg string, a ...slog.Attr) {
+	log.log(slog.LevelWarn, msg, a...)
 }
 
-func (log *logger) Error(msg string, args ...any) {
-	log.log(slog.LevelError, msg, args...)
+func (log *logger) Error(msg string, a ...slog.Attr) {
+	log.log(slog.LevelError, msg, a...)
 }
 
 // Fatal is the same as Error, but quits the program via os.Exit(1).
-func (log *logger) Fatal(msg string, args ...any) {
-	log.log(slog.LevelError, msg, args...)
+func (log *logger) Fatal(msg string, a ...slog.Attr) {
+	log.log(slog.LevelError, msg, a...)
 	os.Exit(1)
 }
 
-func (log *logger) With(args ...any) Logger {
-	context := make([]any, 0, len(log.context)+len(args))
-	context = append(context, log.context...)
-	context = append(context, args...)
-
+func (log *logger) With(a ...slog.Attr) Logger {
 	return &logger{
-		l:       log.l,
-		context: context,
+		l: slog.New(log.l.Handler().WithAttrs(a)),
 	}
 }