journslog: integrate with testing/slogtest

journslog/handler_option.go

@@ -81,3 +81,11 @@ func WithAttrsFromTime(attrsFromTime func(time.Time) []slog.Attr) HandlerOption
 		jh.attrsFromTime = attrsFromTime
 	}
 }
+
+// WithAttrsFromLevel supplies a function which can optionally map the given
+// log level onto zero or more attributes.
+func WithAttrsFromLevel(attrsFromLevel func(slog.Level) []slog.Attr) HandlerOption {
+	return func(jh *JournalHandler) {
+		jh.attrsFromLevel = attrsFromLevel
+	}
+}

journslog/journslog.go

@@ -62,6 +62,10 @@ type JournalHandler struct {
 	// Time from an [slog.Record]. It may be nil.
 	attrsFromTime func(time.Time) []slog.Attr
 
+	// attrsFromLevel may return zero or more attributes to represent the
+	// log level. It may be nil.
+	attrsFromLevel func(slog.Level) []slog.Attr
+
 	// groups are the ordered group names added by WithGroup. We need to
 	// maintain the full list, not just a pre-rendered prefix string,
 	// because of the API of replaceAttr.
@@ -174,6 +178,13 @@ func (jh *JournalHandler) Handle(ctx context.Context, rec slog.Record) error {
 		}
 		addAttrs = append(addAttrs, jh.attrsFromContext(ctx)...)
 	}
+	if jh.attrsFromLevel != nil {
+		if addAttrs == nil {
+			addAttrs = attrPoolGet()
+			defer attrPoolPut(addAttrs)
+		}
+		addAttrs = append(addAttrs, jh.attrsFromLevel(rec.Level)...)
+	}
 
 	// 2 for journal.Conn.Entry (MESSAGE and PRIORITY),
 	// 3 for SRC_* (optional but we always allocate space)

journslog/journslog_test.go

@@ -4,7 +4,11 @@ import (
 	"log/slog"
 	"net/http"
 	"path/filepath"
+	"strings"
 	"testing"
+	"testing/slogtest"
+	"time"
+	"uuid"
 
 	"src.lwithers.me.uk/go/journal"
 	"src.lwithers.me.uk/go/journal/testsink"
@@ -82,3 +86,97 @@ type slowValue string
 func (s slowValue) LogValue() slog.Value {
 	return slog.StringValue(string(s))
 }
+
+// TestSlog integrates with [testing/slogtest].
+func TestSlog(t *testing.T) {
+	tmpdir := t.TempDir()
+
+	attrsFromTime := func(t time.Time) []slog.Attr {
+		return []slog.Attr{
+			{
+				Key:   "TEST_TIME",
+				Value: slog.StringValue(t.Format(time.RFC3339Nano)),
+			},
+		}
+	}
+
+	attrsFromLevel := func(l slog.Level) []slog.Attr {
+		return []slog.Attr{
+			{
+				Key:   "TEST_LEVEL",
+				Value: slog.StringValue(l.String()),
+			},
+		}
+	}
+
+	// XXX: this relies on [slogtest.Run] executing its test cases
+	// completely sequentially
+	var curSink *testsink.Sink
+
+	newHandler := func(t *testing.T) slog.Handler {
+		sockpath := filepath.Join(tmpdir, uuid.New().String())
+		sink, err := testsink.New(sockpath)
+		if err != nil {
+			t.Fatalf("failed to create test sink: %v", err)
+		}
+
+		conn, err := journal.Connect(sockpath)
+		if err != nil {
+			sink.Stop()
+			t.Fatalf("failed to connect to test sink socket: %v", err)
+		}
+
+		h, err := NewHandler(WithConn(conn), WithAttrsFromTime(attrsFromTime), WithAttrsFromLevel(attrsFromLevel), WithHandlerOptions(slog.HandlerOptions{
+			Level: slog.LevelInfo,
+		}))
+		if err != nil {
+			sink.Stop()
+			t.Fatalf("failed to create handler: %v", err)
+		}
+
+		curSink = sink
+		return h
+	}
+
+	result := func(t *testing.T) map[string]any {
+		defer curSink.Stop()
+
+		m, err := curSink.Message(0)
+		if err != nil {
+			t.Fatalf("failed to fetch message from test sink: %v", err)
+		}
+
+		msg, attrs, err := m.Decode()
+		if err != nil {
+			t.Errorf("failed to decode message from test sink: %v", err)
+		}
+
+		out := make(map[string]any)
+		out[slog.MessageKey] = msg
+		for i := range attrs {
+			k, v := attrs[i].Key, attrs[i].Val
+			switch k {
+			case "TEST_TIME":
+				out[slog.TimeKey] = v
+			case "TEST_LEVEL":
+				out[slog.LevelKey] = v
+			default:
+				parts := strings.Split(k, "_")
+				Ng := len(parts) - 1 // number of groups
+				g := out
+				for i := range Ng {
+					next, _ := g[parts[i]].(map[string]any)
+					if next == nil {
+						next = make(map[string]any)
+						g[parts[i]] = next
+					}
+					g = next
+				}
+				g[strings.ToLower(parts[Ng])] = v
+			}
+		}
+		return out
+	}
+
+	slogtest.Run(t, newHandler, result)
+}