[Feature] Add experiment zapslog package to integrate with slog (#1246

)

Ref #1179

This PR provides a implementation of `slog.Handler` in a separate
experiment `exp/zapslog` module as suggested by @abhinav.

Makefile

@@ -8,7 +8,7 @@ BENCH_FLAGS ?= -cpuprofile=cpu.pprof -memprofile=mem.pprof -benchmem
 # Directories containing independent Go modules.
 #
 # We track coverage only for the main module.
-MODULE_DIRS = . ./benchmarks ./zapgrpc/internal/test
+MODULE_DIRS = . ./exp ./benchmarks ./zapgrpc/internal/test
 
 # Many Go tools take file globs or directories as arguments instead of packages.
 GO_FILES := $(shell \

exp/go.mod

@@ -0,0 +1,17 @@
+module go.uber.org/zap/exp
+
+go 1.19
+
+require (
+	github.com/stretchr/testify v1.8.1
+	go.uber.org/zap v1.24.0
+	golang.org/x/exp v0.0.0-20230315142452-642cacee5cc0
+)
+
+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
+)

exp/go.sum

@@ -0,0 +1,28 @@
+github.com/benbjohnson/clock v1.1.0 h1:Q92kusRqC1XV2MjkWETPvjJVqKetz1OzxZB7mHJLju8=
+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=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+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/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=
+golang.org/x/exp v0.0.0-20230315142452-642cacee5cc0 h1:pVgRXcIictcr+lBQIFeiwuwtDIs4eL21OuM9nyAADmo=
+golang.org/x/exp v0.0.0-20230315142452-642cacee5cc0/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
+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=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

exp/zapslog/doc.go

@@ -0,0 +1,27 @@
+// 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.
+
+// Package zapslog provides an implementation of slog.Handler which writes to
+// the supplied zapcore.Core.
+//
+// Since the slog proposal has not been officially accepted by the creation of this package,
+// we do not want Zap's standard packages to take a dependency on `golang.org/x/exp/slog`.
+// Instead, we provide this separate module as a way for users to integrate Zap with slog.
+package zapslog // import "go.uber.org/zap/exp/zapslog"

exp/zapslog/example_test.go

@@ -0,0 +1,77 @@
+// 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.
+
+package zapslog_test
+
+import (
+	"context"
+	"net"
+	"time"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/exp/zapslog"
+	"golang.org/x/exp/slog"
+)
+
+type Password string
+
+func (p Password) LogValue() slog.Value {
+	return slog.StringValue("REDACTED")
+}
+
+func Example_slog() {
+	logger := zap.NewExample(zap.IncreaseLevel(zap.InfoLevel))
+	defer logger.Sync()
+
+	sl := slog.New(zapslog.NewHandler(logger.Core()))
+	ctx := context.Background()
+
+	sl.Info("user", "name", "Al", "secret", Password("secret"))
+	sl.Error("oops", "err", net.ErrClosed, "status", 500)
+	sl.LogAttrs(
+		ctx,
+		slog.LevelError,
+		"oops",
+		slog.Any("err", net.ErrClosed),
+		slog.Int("status", 500),
+	)
+	sl.Info("message",
+		slog.Group("group",
+			slog.Float64("pi", 3.14),
+			slog.Duration("1min", time.Minute),
+		),
+	)
+	sl.WithGroup("s").LogAttrs(
+		ctx,
+		slog.LevelWarn,
+		"warn msg", // message
+		slog.Uint64("u", 1),
+		slog.Any("m", map[string]any{
+			"foo": "bar",
+		}))
+	sl.LogAttrs(ctx, slog.LevelDebug, "not show up")
+
+	// Output:
+	// {"level":"info","msg":"user","name":"Al","secret":"REDACTED"}
+	// {"level":"error","msg":"oops","err":"use of closed network connection","status":500}
+	// {"level":"error","msg":"oops","err":"use of closed network connection","status":500}
+	// {"level":"info","msg":"message","group":{"pi":3.14,"1min":"1m0s"}}
+	// {"level":"warn","msg":"warn msg","s":{"u":1,"m":{"foo":"bar"}}}
+}

exp/zapslog/slog.go

@@ -0,0 +1,187 @@
+// 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.
+
+package zapslog
+
+import (
+	"context"
+	"runtime"
+
+	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
+	"golang.org/x/exp/slog"
+)
+
+// 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
+}
+
+// New builds a [Handler] that writes to the supplied [zapcore.Core].
+// This handler may be supplied to [slog.New] to create a new [slog.Logger].
+func (opts HandlerOptions) New(core zapcore.Core) *Handler {
+	return &Handler{
+		core:      core,
+		name:      opts.LoggerName,
+		addSource: opts.AddSource,
+	}
+}
+
+// NewHandler builds a [Handler] that writes to the supplied [zapcore.Core]
+// with the default options.
+func NewHandler(core zapcore.Core) *Handler {
+	var opts HandlerOptions
+	return opts.New(core)
+}
+
+var _ slog.Handler = (*Handler)(nil)
+
+// groupObject holds all the Attrs saved in a slog.GroupValue.
+type groupObject []slog.Attr
+
+func (gs groupObject) MarshalLogObject(enc zapcore.ObjectEncoder) error {
+	for _, attr := range gs {
+		convertAttrToField(attr).AddTo(enc)
+	}
+	return nil
+}
+
+func convertAttrToField(attr slog.Attr) zapcore.Field {
+	switch attr.Value.Kind() {
+	case slog.KindBool:
+		return zap.Bool(attr.Key, attr.Value.Bool())
+	case slog.KindDuration:
+		return zap.Duration(attr.Key, attr.Value.Duration())
+	case slog.KindFloat64:
+		return zap.Float64(attr.Key, attr.Value.Float64())
+	case slog.KindInt64:
+		return zap.Int64(attr.Key, attr.Value.Int64())
+	case slog.KindString:
+		return zap.String(attr.Key, attr.Value.String())
+	case slog.KindTime:
+		return zap.Time(attr.Key, attr.Value.Time())
+	case slog.KindUint64:
+		return zap.Uint64(attr.Key, attr.Value.Uint64())
+	case slog.KindGroup:
+		return zap.Object(attr.Key, groupObject(attr.Value.Group()))
+	case slog.KindLogValuer:
+		return convertAttrToField(slog.Attr{
+			Key: attr.Key,
+			// TODO: resolve the value in a lazy way
+			Value: attr.Value.Resolve(),
+		})
+	default:
+		return zap.Any(attr.Key, attr.Value.Any())
+	}
+}
+
+// convertSlogLevel maps slog Levels to zap Levels.
+// Note that there is some room between slog levels while zap levels are continuous, so we can't 1:1 map them.
+// See also https://go.googlesource.com/proposal/+/master/design/56345-structured-logging.md?pli=1#levels
+func convertSlogLevel(l slog.Level) zapcore.Level {
+	switch {
+	case l >= slog.LevelError:
+		return zapcore.ErrorLevel
+	case l >= slog.LevelWarn:
+		return zapcore.WarnLevel
+	case l >= slog.LevelInfo:
+		return zapcore.InfoLevel
+	default:
+		return zapcore.DebugLevel
+	}
+}
+
+// Enabled reports whether the handler handles records at the given level.
+func (h *Handler) Enabled(ctx context.Context, level slog.Level) bool {
+	return h.core.Enabled(convertSlogLevel(level))
+}
+
+// Handle handles the Record.
+func (h *Handler) Handle(ctx context.Context, record slog.Record) error {
+	ent := zapcore.Entry{
+		Level:      convertSlogLevel(record.Level),
+		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 {
+		frame, _ := runtime.CallersFrames([]uintptr{record.PC}).Next()
+		ce.Caller = zapcore.EntryCaller{
+			Defined:  true,
+			PC:       frame.PC,
+			File:     frame.File,
+			Line:     frame.Line,
+			Function: frame.Function,
+		}
+	}
+
+	fields := make([]zapcore.Field, 0, record.NumAttrs())
+	record.Attrs(func(attr slog.Attr) {
+		fields = append(fields, convertAttrToField(attr))
+	})
+	ce.Write(fields...)
+	return nil
+}
+
+// WithAttrs returns a new Handler whose attributes consist of
+// both the receiver's attributes and the arguments.
+func (h *Handler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	fields := make([]zapcore.Field, len(attrs))
+	for i, attr := range attrs {
+		fields[i] = convertAttrToField(attr)
+	}
+	return h.withFields(fields...)
+}
+
+// WithGroup returns a new Handler with the given group appended to
+// the receiver's existing groups.
+func (h *Handler) WithGroup(group string) slog.Handler {
+	return h.withFields(zap.Namespace(group))
+}
+
+// withFields returns a cloned Handler with the given fields.
+func (h *Handler) withFields(fields ...zapcore.Field) *Handler {
+	cloned := *h
+	cloned.core = h.core.With(fields)
+	return &cloned
+}

exp/zapslog/slog_test.go

@@ -0,0 +1,48 @@
+// 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.
+
+package zapslog
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap/zapcore"
+	"go.uber.org/zap/zaptest/observer"
+	"golang.org/x/exp/slog"
+)
+
+func TestAddSource(t *testing.T) {
+	r := require.New(t)
+	fac, logs := observer.New(zapcore.DebugLevel)
+	sl := slog.New(HandlerOptions{
+		AddSource: true,
+	}.New(fac))
+	sl.Info("msg")
+
+	r.Len(logs.AllUntimed(), 1, "Expected exactly one entry to be logged")
+	entry := logs.AllUntimed()[0]
+	r.Equal("msg", entry.Entry.Message, "Unexpected message")
+	r.Regexp(
+		`/slog_test.go:\d+$`,
+		entry.Caller.String(),
+		"Unexpected caller annotation.",
+	)
+}