improved error dumping in attrs

slog/attr.go

@@ -97,7 +97,7 @@ func (s Attrs) SerializeValueTo(pc *PrintCtx) {
 	serializeAttrs(pc, s)
 }
 
-func serializeAttrs(pc *PrintCtx, kvps Attrs) { //nolint:revive
+func serializeAttrs(pc *PrintCtx, kvps Attrs) (err error) { //nolint:revive
 	prefix := pc.prefix
 	for _, v := range kvps {
 		if pc.noColor {
@@ -157,13 +157,17 @@ func serializeAttrs(pc *PrintCtx, kvps Attrs) { //nolint:revive
 			pc.valueStringer.WriteValue(val)
 		} else {
 			pc.appendValue(val)
+			if e, ok := val.(error); ok && e != nil {
+				err = e
+			}
 		}
 		pc.prefix = prefix
 	}
 
 	if !pc.noColor {
 		ct.echoResetColor(pc)
 	}
+	return
 }
 
 // type canSerializeValue interface {

slog/entry.go

@@ -1121,14 +1121,38 @@ func (s *Entry) printImpl(ctx context.Context, pc *PrintCtx) (ret []byte) {
 		s.printFirstLineOfMsg(ctx, pc)
 	}
 
-	serializeAttrs(pc, pc.kvps)
+	holded := serializeAttrs(pc, pc.kvps)
 
 	if IsAnyBitsSet(Lcaller) {
 		s.printPC(ctx, pc)
 	}
 
 	s.printRestLinesOfMsg(ctx, pc)
 
+	if pc.lvl <= ErrorLevel && holded != nil && (is.DebugMode() || is.DebugBuild()) {
+		var stackInfo string
+		if _, ok := holded.(interface{ Format(s fmt.State, verb rune) }); ok {
+			stackInfo = fmt.Sprintf("%+v", holded)
+		} else {
+			var x Stringer
+			if x, ok = holded.(Stringer); ok {
+				stackInfo = x.String() // special for those illegal error impl like toml.DecodeError, which have no Format
+			} else {
+				stackInfo = fmt.Sprintf("%v", holded)
+			}
+		}
+		if pc.jsonMode {
+			pc.pcAppendStringKey("errDetail")
+			pc.pcAppendColon()
+			pc.pcAppendStringValue(stackInfo)
+			pc.pcAppendComma()
+		} else {
+			pc.pcAppendByte('\n')
+			txt := ct.pad(stackInfo, "    ", 1)
+			ct.wrapColorAndBgTo(pc, red, clrLoggerNameBg, txt)
+		}
+	}
+
 	if pc.jsonMode {
 		pc.pcAppendByte('}')
 	}
@@ -1159,12 +1183,15 @@ func (s *Entry) printTimestamp(ctx context.Context, pc *PrintCtx) {
 func (s *Entry) printLoggerName(ctx context.Context, pc *PrintCtx) {
 	if s.name != "" {
 		if pc.noColor { // json or logfmt
-			pc.AddString("logger", s.name)
-			// pc.pcAppendStringKey("logger")
-			// pc.pcAppendColon()
-			// pc.pcAppendByte('"')
-			// pc.pcAppendStringValue(s.name)
-			// pc.pcAppendByte('"')
+			if pc.jsonMode {
+				pc.pcAppendStringKey("logger")
+				pc.pcAppendColon()
+				pc.pcAppendByte('"')
+				pc.pcAppendStringValue(s.name)
+				pc.pcAppendByte('"')
+			} else {
+				pc.AddString("logger", s.name)
+			}
 			pc.pcAppendComma()
 		} else {
 			ct.wrapColorAndBgTo(pc, clrLoggerName, clrLoggerNameBg, s.name)