fix: prevent logger close recursion and unsafe writer closing

logger_test.go

@@ -0,0 +1,170 @@
+package slog
+
+import (
+	"bytes"
+	"errors"
+	"os"
+	"testing"
+)
+
+type stubLoggerWriter struct {
+	printErr   error
+	closeErr   error
+	printCalls int
+	closeCalls int
+}
+
+func (w *stubLoggerWriter) Close() error {
+	w.closeCalls++
+	return w.closeErr
+}
+
+func (w *stubLoggerWriter) Write(p []byte) (int, error) {
+	return len(p), nil
+}
+
+func (w *stubLoggerWriter) Print(_ LogLevel, _ string, _ []*MethodTraceback, _ ...any) error {
+	w.printCalls++
+	return w.printErr
+}
+
+func TestLoggerCloseReturnsJoinedErrorsWithoutRelogging(t *testing.T) {
+	firstErr := errors.New("first close failed")
+	secondErr := errors.New("second close failed")
+	first := &stubLoggerWriter{closeErr: firstErr}
+	second := &stubLoggerWriter{closeErr: secondErr}
+
+	logger := CreateLogger().AddWriters(first, second)
+	err := logger.Close()
+	if !errors.Is(err, firstErr) {
+		t.Fatalf("Close() error should include first writer error, got %v", err)
+	}
+	if !errors.Is(err, secondErr) {
+		t.Fatalf("Close() error should include second writer error, got %v", err)
+	}
+	if first.printCalls != 0 || second.printCalls != 0 {
+		t.Fatalf("Close() should not log through writers again, got print calls first=%d second=%d", first.printCalls, second.printCalls)
+	}
+	if first.closeCalls != 1 || second.closeCalls != 1 {
+		t.Fatalf("Close() should close each writer once, got close calls first=%d second=%d", first.closeCalls, second.closeCalls)
+	}
+	if err := logger.Close(); err != nil {
+		t.Fatalf("second Close() should be a no-op, got %v", err)
+	}
+}
+
+func TestLoggerPrintDoesNotRecurseOnWriterError(t *testing.T) {
+	oldStderr := os.Stderr
+	stderrFile, err := os.CreateTemp(t.TempDir(), "stderr")
+	if err != nil {
+		t.Fatalf("CreateTemp() error = %v", err)
+	}
+	os.Stderr = stderrFile
+	t.Cleanup(func() {
+		os.Stderr = oldStderr
+		_ = stderrFile.Close()
+	})
+
+	bad := &stubLoggerWriter{printErr: errors.New("print failed")}
+	good := &stubLoggerWriter{}
+
+	logger := CreateLogger().AddWriters(bad, good)
+	logger.Error("boom")
+
+	if bad.printCalls != 1 {
+		t.Fatalf("bad writer should be called once, got %d", bad.printCalls)
+	}
+	if good.printCalls != 1 {
+		t.Fatalf("good writer should be called once, got %d", good.printCalls)
+	}
+}
+
+func TestCreateTextWriterCloseOnNonCloserIsNoOp(t *testing.T) {
+	writer := CreateTextWriter(&bytes.Buffer{}, false, false)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+}
+
+func TestCreateTextWriterDoesNotCloseExternalCloser(t *testing.T) {
+	file, err := os.CreateTemp(t.TempDir(), "text-writer")
+	if err != nil {
+		t.Fatalf("CreateTemp() error = %v", err)
+	}
+	t.Cleanup(func() {
+		_ = file.Close()
+	})
+
+	writer := CreateTextWriter(file, false, false)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+	if _, err := file.WriteString("still open"); err != nil {
+		t.Fatalf("CreateTextWriter() should not close external writers, got %v", err)
+	}
+}
+
+func TestCreateJsonWriterCloseOnNonCloserIsNoOp(t *testing.T) {
+	writer := CreateJsonWriter(&bytes.Buffer{}, false)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+}
+
+func TestCreateJsonWriterDoesNotCloseExternalCloser(t *testing.T) {
+	file, err := os.CreateTemp(t.TempDir(), "json-writer")
+	if err != nil {
+		t.Fatalf("CreateTemp() error = %v", err)
+	}
+	t.Cleanup(func() {
+		_ = file.Close()
+	})
+
+	writer := CreateJsonWriter(file, false)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+	if _, err := file.WriteString("still open"); err != nil {
+		t.Fatalf("CreateJsonWriter() should not close external writers, got %v", err)
+	}
+}
+
+func TestCreateTextStdoutWriterDoesNotCloseStdout(t *testing.T) {
+	stdoutFile := swapStdout(t)
+
+	writer := CreateTextStdoutWriter(false, false)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+	if _, err := stdoutFile.WriteString("still open"); err != nil {
+		t.Fatalf("stdout writer Close() should not close stdout, got %v", err)
+	}
+}
+
+func TestCreateJsonStdoutWriterDoesNotCloseStdout(t *testing.T) {
+	stdoutFile := swapStdout(t)
+
+	writer := CreateJsonStdoutWriter(false)
+	if err := writer.Close(); err != nil {
+		t.Fatalf("Close() error = %v", err)
+	}
+	if _, err := stdoutFile.WriteString("still open"); err != nil {
+		t.Fatalf("stdout writer Close() should not close stdout, got %v", err)
+	}
+}
+
+func swapStdout(t *testing.T) *os.File {
+	t.Helper()
+
+	oldStdout := os.Stdout
+	stdoutFile, err := os.CreateTemp(t.TempDir(), "stdout")
+	if err != nil {
+		t.Fatalf("CreateTemp() error = %v", err)
+	}
+	os.Stdout = stdoutFile
+	t.Cleanup(func() {
+		os.Stdout = oldStdout
+		_ = stdoutFile.Close()
+	})
+	return stdoutFile
+}