feat(zapslog): implement stack trace handling

exp/go.mod

@@ -10,7 +10,8 @@ require (
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
-	go.uber.org/atomic v1.10.0 // indirect
 	go.uber.org/multierr v1.10.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )
+
+replace go.uber.org/zap => ../

exp/go.sum

@@ -1,8 +1,7 @@
-github.com/benbjohnson/clock v1.1.0 h1:Q92kusRqC1XV2MjkWETPvjJVqKetz1OzxZB7mHJLju8=
+github.com/benbjohnson/clock v1.3.0 h1:ip6w0uFQkncKQ979AypyG0ER7mqUSBdKLOgAle/AT8A=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
@@ -12,13 +11,9 @@ github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
 github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-go.uber.org/atomic v1.10.0 h1:9qC72Qh0+3MqyJbAn8YU5xVq1frD8bn3JtD2oXtafVQ=
-go.uber.org/atomic v1.10.0/go.mod h1:LUxbIzbOniOlMKjJjyPfpl4v+PKK2cNJn91OQbhoJI0=
-go.uber.org/goleak v1.1.11 h1:wy28qYRKZgnJTxGxvye5/wgWr1EKjmUDGYox5mGlRlI=
+go.uber.org/goleak v1.2.0 h1:xqgm/S+aQvhWFTtR0XK3Jvg7z8kGV8P4X14IzwN3Eqk=
 go.uber.org/multierr v1.10.0 h1:S0h4aNzvfcFsC3dRF1jLoaov7oRaKqRGC/pUEJ2yvPQ=
 go.uber.org/multierr v1.10.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
-go.uber.org/zap v1.24.0 h1:FiJd5l1UOLj0wCgbSE0rwwXHzEdAZS6hiiSnxJN/D60=
-go.uber.org/zap v1.24.0/go.mod h1:2kMP+WWQ8aoFoedH3T2sq6iJ2yDWpHbP0f6MQbS9Gkg=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

exp/zapslog/example_test.go

@@ -42,7 +42,7 @@ func Example_slog() {
 	logger := zap.NewExample(zap.IncreaseLevel(zap.InfoLevel))
 	defer logger.Sync()
 
-	sl := slog.New(zapslog.NewHandler(logger.Core(), nil /* options */))
+	sl := slog.New(zapslog.NewHandler(logger.Core()))
 	ctx := context.Background()
 
 	sl.Info("user", "name", "Al", "secret", Password("secret"))

exp/zapslog/handler.go

@@ -28,41 +28,30 @@ import (
 	"runtime"
 
 	"go.uber.org/zap"
+	"go.uber.org/zap/internal/stacktrace"
 	"go.uber.org/zap/zapcore"
 )
 
 // Handler implements the slog.Handler by writing to a zap Core.
 type Handler struct {
-	core      zapcore.Core
-	name      string // logger name
-	addSource bool
-}
-
-// HandlerOptions are options for a Zap-based [slog.Handler].
-type HandlerOptions struct {
-	// LoggerName is used for log entries received from slog.
-	//
-	// Defaults to empty.
-	LoggerName string
-
-	// AddSource configures the handler to annotate each message with the filename,
-	// line number, and function name.
-	// AddSource is false by default to skip the cost of computing
-	// this information.
-	AddSource bool
+	core       zapcore.Core
+	name       string // logger name
+	addCaller  bool
+	addStackAt slog.Level
+	callerSkip int
 }
 
 // NewHandler builds a [Handler] that writes to the supplied [zapcore.Core]
-// with the default options.
-func NewHandler(core zapcore.Core, opts *HandlerOptions) *Handler {
-	if opts == nil {
-		opts = &HandlerOptions{}
+// with options.
+func NewHandler(core zapcore.Core, opts ...Option) *Handler {
+	h := &Handler{
+		core:       core,
+		addStackAt: slog.LevelError,
 	}
-	return &Handler{
-		core:      core,
-		name:      opts.LoggerName,
-		addSource: opts.AddSource,
+	for _, v := range opts {
+		v.apply(h)
 	}
+	return h
 }
 
 var _ slog.Handler = (*Handler)(nil)
@@ -136,15 +125,13 @@ func (h *Handler) Handle(ctx context.Context, record slog.Record) error {
 		Time:       record.Time,
 		Message:    record.Message,
 		LoggerName: h.name,
-		// TODO: do we need to set the following fields?
-		// Stack:
 	}
 	ce := h.core.Check(ent, nil)
 	if ce == nil {
 		return nil
 	}
 
-	if h.addSource && record.PC != 0 {
+	if h.addCaller && record.PC != 0 {
 		frame, _ := runtime.CallersFrames([]uintptr{record.PC}).Next()
 		if frame.PC != 0 {
 			ce.Caller = zapcore.EntryCaller{
@@ -157,6 +144,14 @@ func (h *Handler) Handle(ctx context.Context, record slog.Record) error {
 		}
 	}
 
+	if record.Level >= h.addStackAt {
+		// Skipping 3:
+		// zapslog/handler log/slog.(*Logger).log
+		// slog/logger log/slog.(*Logger).log
+		// slog/logger log/slog.(*Logger).<level>
+		ce.Stack = stacktrace.Take(3 + h.callerSkip)
+	}
+
 	fields := make([]zapcore.Field, 0, record.NumAttrs())
 	record.Attrs(func(attr slog.Attr) bool {
 		if attr.Equal(slog.Attr{}) {

exp/zapslog/handler_test.go

@@ -32,13 +32,11 @@ import (
 	"go.uber.org/zap/zaptest/observer"
 )
 
-func TestAddSource(t *testing.T) {
+func TestAddCaller(t *testing.T) {
 	t.Parallel()
 
 	fac, logs := observer.New(zapcore.DebugLevel)
-	sl := slog.New(NewHandler(fac, &HandlerOptions{
-		AddSource: true,
-	}))
+	sl := slog.New(NewHandler(fac, WithCaller(true)))
 	sl.Info("msg")
 
 	require.Len(t, logs.AllUntimed(), 1, "Expected exactly one entry to be logged")
@@ -51,11 +49,31 @@ func TestAddSource(t *testing.T) {
 	)
 }
 
+func TestAddStack(t *testing.T) {
+	fac, logs := observer.New(zapcore.DebugLevel)
+	sl := slog.New(NewHandler(fac, AddStacktraceAt(slog.LevelDebug)))
+	sl.Info("msg")
+
+	require.Len(t, logs.AllUntimed(), 1, "Expected exactly one entry to be logged")
+	entry := logs.AllUntimed()[0]
+	require.Equal(t, "msg", entry.Message, "Unexpected message")
+	assert.Regexp(t,
+		`^go.uber.org/zap/exp/zapslog.TestAddStack`,
+		entry.Stack,
+		"Unexpected stack trace annotation.",
+	)
+	assert.Regexp(t,
+		`/zapslog/handler_test.go:\d+`,
+		entry.Stack,
+		"Unexpected stack trace annotation.",
+	)
+}
+
 func TestEmptyAttr(t *testing.T) {
 	t.Parallel()
 
 	fac, observedLogs := observer.New(zapcore.DebugLevel)
-	sl := slog.New(NewHandler(fac, nil))
+	sl := slog.New(NewHandler(fac))
 
 	t.Run("Handle", func(t *testing.T) {
 		sl.Info(

exp/zapslog/options.go

@@ -0,0 +1,72 @@
+// Copyright (c) 2023 Uber Technologies, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+
+//go:build go1.21
+
+package zapslog
+
+import "log/slog"
+
+// An Option configures a slog Handler.
+type Option interface {
+	apply(*Handler)
+}
+
+// optionFunc wraps a func so it satisfies the Option interface.
+type optionFunc func(*Handler)
+
+func (f optionFunc) apply(handler *Handler) {
+	f(handler)
+}
+
+// WithName configures the Logger to annotate each message with the logger name.
+func WithName(name string) Option {
+	return optionFunc(func(h *Handler) {
+		h.name = name
+	})
+}
+
+// WithCaller configures the Logger to include the filename and line number
+// of the caller in log messages--if available.
+func WithCaller(enabled bool) Option {
+	return optionFunc(func(handler *Handler) {
+		handler.addCaller = enabled
+	})
+}
+
+// WithCallerSkip increases the number of callers skipped by caller annotation
+// (as enabled by the [WithCaller] option).
+//
+// When building wrappers around the Logger,
+// supplying this Option prevents Zap from always reporting
+// the wrapper code as the caller.
+func WithCallerSkip(skip int) Option {
+	return optionFunc(func(log *Handler) {
+		log.callerSkip += skip
+	})
+}
+
+// AddStacktraceAt configures the Logger to record a stack trace
+// for all messages at or above a given level.
+func AddStacktraceAt(lvl slog.Level) Option {
+	return optionFunc(func(log *Handler) {
+		log.addStackAt = lvl
+	})
+}