feat: modify slog.Logger to *not* implement slog.Sink (#95)

The prior implementation allowed slog.Logger instances
to themselves be passes as slog.Sink targets. This enabled
many usage patterns that introduced extremely counter-intuitive
behavior.

Author: cmoog

example_helper_test.go

@@ -17,7 +17,7 @@ func httpLogHelper(ctx context.Context, status int) {
 	)
 }
 
-var l = sloghuman.Make(os.Stdout)
+var l = slog.Make(sloghuman.Sink(os.Stdout))
 
 func ExampleHelper() {
 	ctx := context.Background()

example_marshaller_test.go

@@ -21,7 +21,7 @@ func (s myStruct) MarshalJSON() ([]byte, error) {
 }
 
 func Example_marshaller() {
-	l := sloghuman.Make(os.Stdout)
+	l := slog.Make(sloghuman.Sink(os.Stdout))
 
 	l.Info(context.Background(), "wow",
 		slog.F("myStruct", myStruct{

example_test.go

@@ -18,7 +18,7 @@ import (
 )
 
 func Example() {
-	log := sloghuman.Make(os.Stdout)
+	log := slog.Make(sloghuman.Sink(os.Stdout))
 
 	log.Info(context.Background(), "my message here",
 		slog.F("field_name", "something or the other"),
@@ -45,7 +45,7 @@ func Example() {
 }
 
 func Example_struct() {
-	l := sloghuman.Make(os.Stdout)
+	l := slog.Make(sloghuman.Sink(os.Stdout))
 
 	type hello struct {
 		Meow int       `json:"meow"`
@@ -76,7 +76,7 @@ func Example_testing() {
 }
 
 func Example_tracing() {
-	log := sloghuman.Make(os.Stdout)
+	log := slog.Make(sloghuman.Sink(os.Stdout))
 
 	ctx, _ := trace.StartSpan(context.Background(), "spanName")
 
@@ -86,14 +86,14 @@ func Example_tracing() {
 }
 
 func Example_multiple() {
-	l := sloghuman.Make(os.Stdout)
+	l := slog.Make(sloghuman.Sink(os.Stdout))
 
 	f, err := os.OpenFile("stackdriver", os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0644)
 	if err != nil {
 		l.Fatal(context.Background(), "failed to open stackdriver log file", slog.Error(err))
 	}
 
-	l = slog.Make(l, slogstackdriver.Make(f))
+	l = l.AppendSinks(slogstackdriver.Sink(f))
 
 	l.Info(context.Background(), "log to stdout and stackdriver")
 
@@ -103,15 +103,15 @@ func Example_multiple() {
 func ExampleWith() {
 	ctx := slog.With(context.Background(), slog.F("field", 1))
 
-	l := sloghuman.Make(os.Stdout)
+	l := slog.Make(sloghuman.Sink(os.Stdout))
 	l.Info(ctx, "msg")
 
 	// 2019-12-07 20:54:23.986 [INFO]	<example_test.go:20>	msg	{"field": 1}
 }
 
 func ExampleStdlib() {
 	ctx := slog.With(context.Background(), slog.F("field", 1))
-	l := slog.Stdlib(ctx, sloghuman.Make(os.Stdout))
+	l := slog.Stdlib(ctx, slog.Make(sloghuman.Sink(os.Stdout)))
 
 	l.Print("msg")
 
@@ -121,7 +121,7 @@ func ExampleStdlib() {
 func ExampleLogger_Named() {
 	ctx := context.Background()
 
-	l := sloghuman.Make(os.Stdout)
+	l := slog.Make(sloghuman.Sink(os.Stdout))
 	l = l.Named("http")
 	l.Info(ctx, "received request", slog.F("remote address", net.IPv4(127, 0, 0, 1)))
 
@@ -131,7 +131,7 @@ func ExampleLogger_Named() {
 func ExampleLogger_Leveled() {
 	ctx := context.Background()
 
-	l := sloghuman.Make(os.Stdout)
+	l := slog.Make(sloghuman.Sink(os.Stdout))
 	l.Debug(ctx, "testing1")
 	l.Info(ctx, "received request")
 

go.sum

@@ -14,7 +14,7 @@ func TestStdlib(t *testing.T) {
 	t.Parallel()
 
 	b := &bytes.Buffer{}
-	l := slog.Make(sloghuman.Make(b)).With(
+	l := slog.Make(sloghuman.Sink(b)).With(
 		slog.F("hi", "we"),
 	)
 	stdlibLog := slog.Stdlib(bg, l)

s_test.go

@@ -29,11 +29,11 @@ type Sink interface {
 	Sync()
 }
 
-// LogEntry logs the given entry with the context to the
+// Log logs the given entry with the context to the
 // underlying sinks.
 //
 // It extends the entry with the set fields and names.
-func (l Logger) LogEntry(ctx context.Context, e SinkEntry) {
+func (l Logger) Log(ctx context.Context, e SinkEntry) {
 	if e.Level < l.level {
 		return
 	}
@@ -138,17 +138,19 @@ func (l Logger) Named(name string) Logger {
 func (l Logger) Leveled(level Level) Logger {
 	l.level = level
 	l.sinks = append([]Sink(nil), l.sinks...)
-	for i, s := range l.sinks {
-		if l2, ok := s.(Logger); ok {
-			l.sinks[i] = l2.Leveled(level)
-		}
-	}
+	return l
+}
+
+// AppendSinks appends the sinks to the set sink
+// targets on the logger.
+func (l Logger) AppendSinks(s ...Sink) Logger {
+	l.sinks = append(l.sinks, s...)
 	return l
 }
 
 func (l Logger) log(ctx context.Context, level Level, msg string, fields Map) {
 	ent := l.entry(ctx, level, msg, fields)
-	l.LogEntry(ctx, ent)
+	l.Log(ctx, ent)
 }
 
 func (l Logger) entry(ctx context.Context, level Level, msg string, fields Map) SinkEntry {

slog.go

@@ -38,8 +38,9 @@ func TestLogger(t *testing.T) {
 
 		s1 := &fakeSink{}
 		s2 := &fakeSink{}
-		l := slog.Make(s1, s2)
+		l := slog.Make(s1)
 		l = l.Leveled(slog.LevelError)
+		l = l.AppendSinks(s2)
 
 		l.Info(bg, "wow", slog.Error(io.EOF))
 		l.Error(bg, "meow", slog.Error(io.ErrUnexpectedEOF))
@@ -74,7 +75,7 @@ func TestLogger(t *testing.T) {
 
 			File: slogTestFile,
 			Func: "cdr.dev/slog_test.TestLogger.func2",
-			Line: 66,
+			Line: 67,
 
 			Fields: slog.M(
 				slog.F("ctx", 1024),
@@ -107,7 +108,7 @@ func TestLogger(t *testing.T) {
 
 			File: slogTestFile,
 			Func: "cdr.dev/slog_test.TestLogger.func3",
-			Line: 97,
+			Line: 98,
 
 			SpanContext: span.SpanContext(),
 

slog_test.go

@@ -12,16 +12,16 @@ import (
 	"cdr.dev/slog/internal/syncwriter"
 )
 
-// Make creates a logger that writes logs in a human
+// Sink creates a slog.Sink that writes logs in a human
 // readable YAML like format to the given writer.
 //
 // If the writer implements Sync() error then
 // it will be called when syncing.
-func Make(w io.Writer) slog.Logger {
-	return slog.Make(&humanSink{
+func Sink(w io.Writer) slog.Sink {
+	return &humanSink{
 		w:  syncwriter.New(w),
 		w2: w,
-	})
+	}
 }
 
 type humanSink struct {

sloggers/sloghuman/sloghuman.go

@@ -17,7 +17,7 @@ func TestMake(t *testing.T) {
 	t.Parallel()
 
 	b := &bytes.Buffer{}
-	l := sloghuman.Make(b)
+	l := slog.Make(sloghuman.Sink(b))
 	l.Info(bg, "line1\n\nline2", slog.F("wowow", "me\nyou"))
 	l.Sync()
 

sloggers/sloghuman/sloghuman_test.go

@@ -29,12 +29,12 @@ import (
 	"cdr.dev/slog/internal/syncwriter"
 )
 
-// Make creates a logger that writes JSON logs
+// Sink creates a slog.Sink that writes JSON logs
 // to the given writer. See package level docs
 // for the format.
 // If the writer implements Sync() error then
 // it will be called when syncing.
-func Make(w io.Writer) slog.Logger {
+func Sink(w io.Writer) slog.Logger {
 	return slog.Make(jsonSink{
 		w: syncwriter.New(w),
 	})

sloggers/slogjson/slogjson.go

@@ -24,7 +24,7 @@ func TestMake(t *testing.T) {
 
 	ctx, s := trace.StartSpan(bg, "meow")
 	b := &bytes.Buffer{}
-	l := slogjson.Make(b)
+	l := slogjson.Sink(b)
 	l = l.Named("named")
 	l.Error(ctx, "line1\n\nline2", slog.F("wowow", "me\nyou"))
 

sloggers/slogjson/slogjson_test.go

@@ -17,17 +17,17 @@ import (
 	"cdr.dev/slog/internal/syncwriter"
 )
 
-// Make creates a slog.Logger configured to write JSON logs
+// Sink creates a slog.Sink configured to write JSON logs
 // to stdout for stackdriver.
 //
 // See https://cloud.google.com/logging/docs/agent
-func Make(w io.Writer) slog.Logger {
+func Sink(w io.Writer) slog.Sink {
 	projectID, _ := metadata.ProjectID()
 
-	return slog.Make(stackdriverSink{
+	return stackdriverSink{
 		projectID: projectID,
 		w:         syncwriter.New(w),
-	})
+	}
 }
 
 type stackdriverSink struct {

sloggers/slogstackdriver/slogstackdriver.go

@@ -25,7 +25,7 @@ func TestStackdriver(t *testing.T) {
 
 	ctx, s := trace.StartSpan(bg, "meow")
 	b := &bytes.Buffer{}
-	l := slogstackdriver.Make(b)
+	l := slog.Make(slogstackdriver.Sink(b))
 	l = l.Named("meow")
 	l.Error(ctx, "line1\n\nline2", slog.F("wowow", "me\nyou"))
 

sloggers/slogstackdriver/slogstackdriver_test.go

@@ -18,7 +18,7 @@ import (
 
 // Ensure all stdlib logs go through slog.
 func init() {
-	l := sloghuman.Make(os.Stderr)
+	l := slog.Make(sloghuman.Sink(os.Stderr))
 	log.SetOutput(slog.Stdlib(context.Background(), l).Writer())
 }
 

sloggers/slogtest/t.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"testing"
 
-	"cdr.dev/slog"
 	"cdr.dev/slog/internal/assert"
 	"cdr.dev/slog/sloggers/slogtest"
 )
@@ -31,9 +30,9 @@ func TestIgnoreErrors(t *testing.T) {
 	t.Parallel()
 
 	tb := &fakeTB{}
-	l := slog.Make(slogtest.Make(tb, &slogtest.Options{
+	l := slogtest.Make(tb, &slogtest.Options{
 		IgnoreErrors: true,
-	}))
+	})
 
 	l.Error(bg, "hello")
 	assert.Equal(t, "errors", 0, tb.errors)