llog: write output to a Writer

Signed-off-by: Chris Koch <[email protected]>

llog/levellog.go

@@ -8,10 +8,12 @@ package llog
 import (
 	"flag"
 	"fmt"
+	"io"
 	"log"
 	"log/slog"
 	"math"
 	"strconv"
+	"strings"
 	"testing"
 )
 
@@ -39,6 +41,32 @@ type Printfer interface {
 	Printf(format string, v ...any)
 }
 
+func lineSprintf(format string, v ...any) string {
+	s := fmt.Sprintf(format, v...)
+	if strings.HasSuffix(s, "\n") {
+		return s
+	}
+	return s + "\n"
+}
+
+// WritePrintf is a Printf that prints lines to w.
+func WritePrintf(w io.Writer) Printf {
+	return func(format string, v ...any) {
+		_ = io.WriteString(w, lineSprintf(format, v...))
+	}
+}
+
+// MultiPrintf is a Printf that prints to all given p.
+func MultiPrintf(p ...Printf) Printf {
+	return func(format string, v ...any) {
+		for _, q := range p {
+			if q != nil {
+				q(format, v...)
+			}
+		}
+	}
+}
+
 // Sink is the output for Logger.
 type Sink func(level slog.Level, format string, v ...any)
 

llog/llog_test.go

@@ -183,3 +183,16 @@ func TestDefaults(t *testing.T) {
 	l = Test(t)
 	l.Debugf("more foobar")
 }
+
+func TestBufOutput(t *testing.T) {
+	var s strings.Builder
+	l := New(slog.LevelDebug, MultiPrintf(nil, t.Logf, WritePrintf(&s)))
+	l.Debugf("test output!")
+	l.Infof("test output\n\n")
+
+	got := s.String()
+	want := "DEBUG test output!\nINFO test output\n\n"
+	if got != want {
+		t.Errorf("got = %v, want %v", got, want)
+	}
+}