[Feature] Add experiment zapslog package to integrate with slog

exp/go.mod

@@ -0,0 +1,13 @@
+module go.uber.org/zap/exp
+
+go 1.19
+
+require (
+	go.uber.org/zap v1.24.0
+	golang.org/x/exp v0.0.0-20230307190834-24139beb5833
+)
+
+require (
+	go.uber.org/atomic v1.7.0 // indirect
+	go.uber.org/multierr v1.6.0 // indirect
+)

exp/go.sum

@@ -0,0 +1,20 @@
+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/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
+go.uber.org/atomic v1.7.0 h1:ADUqmZGgLDDfbSL9ZmPxKTybcoEYHgpYfELNoN+7hsw=
+go.uber.org/atomic v1.7.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
+go.uber.org/goleak v1.1.11 h1:wy28qYRKZgnJTxGxvye5/wgWr1EKjmUDGYox5mGlRlI=
+go.uber.org/multierr v1.6.0 h1:y6IPFStTAIT5Ytl7/XYmHvzXQ7S3g/IeZW9hyZ5thw4=
+go.uber.org/multierr v1.6.0/go.mod h1:cdWPpRnG4AhwMwsgIHip0KRBQjJy5kYEpYjJxpXp9iU=
+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 v0.0.0-20230307190834-24139beb5833 h1:SChBja7BCQewoTAU7IgvucQKMIXrEpFxNMs0spT3/5s=
+golang.org/x/exp v0.0.0-20230307190834-24139beb5833/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

exp/zapslog/doc.go

@@ -0,0 +1,29 @@
+// 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 underlying zap.Logger.
+//
+// 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 package as a way for users to integrate Zap with slog.
+// For users who want to experiment Zap with slog, they can import this package and compile it with
+// the build tag `zapslog`.
+package zapslog // import "go.uber.org/zap/exp/slog"

exp/zapslog/example_test.go

@@ -0,0 +1,68 @@
+// 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"
+	"golang.org/x/exp/slog"
+
+	"go.uber.org/zap/exp/zapslog"
+)
+
+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", 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", 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","s":{"u":1,"m":{"foo":"bar"}}}
+}

exp/zapslog/slog.go

@@ -0,0 +1,145 @@
+// 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"
+
+	"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
+}
+
+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,
+			// FIXME(knight42): 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
+	}
+}
+
+func (h *Handler) Enabled(ctx context.Context, level slog.Level) bool {
+	return h.core.Enabled(convertSlogLevel(level))
+}
+
+func (h *Handler) Handle(ctx context.Context, record slog.Record) error {
+	ent := zapcore.Entry{
+		Level:   convertSlogLevel(record.Level),
+		Time:    record.Time,
+		Message: record.Message,
+		// FIXME: do we need to set the following fields?
+		// LoggerName:
+		// Caller:
+		// Stack:
+	}
+	ce := h.core.Check(ent, nil)
+	if ce == nil {
+		return nil
+	}
+
+	fields := make([]zapcore.Field, 0, record.NumAttrs())
+	record.Attrs(func(attr slog.Attr) {
+		fields = append(fields, convertAttrToField(attr))
+	})
+	ce.Write(fields...)
+	return nil
+}
+
+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...)
+
+}
+
+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 {
+	return &Handler{
+		core: h.core.With(fields),
+	}
+}
+
+// NewHandler returns a *Handler which writes to the supplied zap Core.
+func NewHandler(core zapcore.Core) *Handler {
+	return &Handler{
+		core: core,
+	}
+}