feat(logger): implement slog.Handler (#13)

* feat(logger): implement slog.Handler

This implements slog.Handler interface. You can use Log as an slog
handler.

* feat: compile for go1.20 and go1.21

* refactor: match log/slog level values

* feat: add slog tests

* chore: downgrade the minimum go version to go1.19

* doc: add slog support

* refactor: rename files

* fix: add emoji test

* chore!: change default timestamp and level key names

* fix: lint

.golangci.yml

@@ -23,7 +23,6 @@ linters:
     - goimports
     - goprintffuncname
     - gosec
-    - ifshort
     - misspell
     - nolintlint
     - prealloc
@@ -32,4 +31,4 @@ linters:
     - sqlclosecheck
     - unconvert
     - unparam
-    - whitespace
+    - whitespace

README.md

@@ -34,6 +34,7 @@ readable logging with batteries included.
 - Leveled logging.
 - Text, JSON, and Logfmt formatters.
 - Store and retrieve logger in and from context.
+- Slog handler.
 - Standard log adapter.
 
 ## Usage
@@ -306,6 +307,17 @@ startOven(400) // INFO <cookies/oven.go:123> Starting oven degree=400
 This will use the _caller_ function (`startOven`) line number instead of the
 logging function (`log.Info`) to report the source location.
 
+### Slog Handler
+
+You can use Log as an [`log/slog`](https://pkg.go.dev/log/slog) handler. Just
+pass a logger instance to Slog and you're good to go.
+
+```go
+handler := log.New(os.Stderr)
+logger := slog.New(handler)
+logger.Error("meow?")
+```
+
 ### Standard Log Adapter
 
 Some Go libraries, especially the ones in the standard library, will only accept

context_test.go

@@ -3,7 +3,7 @@ package log
 import (
 	"bytes"
 	"context"
-	"io/ioutil"
+	"io"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -14,7 +14,7 @@ func TestLogContext_empty(t *testing.T) {
 }
 
 func TestLogContext_simple(t *testing.T) {
-	l := New(ioutil.Discard)
+	l := New(io.Discard)
 	ctx := WithContext(context.Background(), l)
 	require.Equal(t, l, FromContext(ctx))
 }

formatter.go

@@ -15,11 +15,11 @@ const (
 
 var (
 	// TimestampKey is the key for the timestamp.
-	TimestampKey = "ts"
+	TimestampKey = "time"
 	// MessageKey is the key for the message.
 	MessageKey = "msg"
 	// LevelKey is the key for the level.
-	LevelKey = "lvl"
+	LevelKey = "level"
 	// CallerKey is the key for the caller.
 	CallerKey = "caller"
 	// PrefixKey is the key for the prefix.

go.mod

@@ -1,12 +1,13 @@
 module github.com/charmbracelet/log
 
-go 1.17
+go 1.19
 
 require (
 	github.com/charmbracelet/lipgloss v0.9.1
 	github.com/go-logfmt/logfmt v0.6.0
 	github.com/muesli/termenv v0.15.2
 	github.com/stretchr/testify v1.8.4
+	golang.org/x/exp v0.0.0-20231006140011-7918f672742d
 )
 
 require (
@@ -18,6 +19,6 @@ require (
 	github.com/muesli/reflow v0.3.0 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/rivo/uniseg v0.2.0 // indirect
-	golang.org/x/sys v0.12.0 // indirect
+	golang.org/x/sys v0.13.0 // indirect
 	gopkg.in/yaml.v3 v3.0.1 // indirect
 )

go.sum

@@ -2,7 +2,6 @@ github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiE
 github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
 github.com/charmbracelet/lipgloss v0.9.1 h1:PNyd3jvaJbg4jRHKWXnCj1akQm4rh8dbEzN1p/u1KWg=
 github.com/charmbracelet/lipgloss v0.9.1/go.mod h1:1mPmG4cxScwUQALAAnacHaigiiHB9Pmr+v1VEawJl6I=
-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/go-logfmt/logfmt v0.6.0 h1:wGYYu3uicYdqXVgoYbvnkrPVXkuLM1p1ifugDMEdRi4=
@@ -12,7 +11,6 @@ github.com/lucasb-eyer/go-colorful v1.2.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i
 github.com/mattn/go-isatty v0.0.18 h1:DOKFKCQ7FNG2L1rbrmstDN4QVRdS89Nkh85u68Uwp98=
 github.com/mattn/go-isatty v0.0.18/go.mod h1:W+V8PltTTMOvKvAeJH7IuucS94S2C6jfK/D7dTCTo3Y=
 github.com/mattn/go-runewidth v0.0.12/go.mod h1:RAqKPSqVFrSLVXbA8x7dzmKdmGzieGRCM46jaSJTDAk=
-github.com/mattn/go-runewidth v0.0.14/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
 github.com/mattn/go-runewidth v0.0.15 h1:UNAjwbU9l54TA3KzvqLGxwWjHmMgBUVhBiTjelZgg3U=
 github.com/mattn/go-runewidth v0.0.15/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
 github.com/muesli/reflow v0.3.0 h1:IFsN6K9NfGtjeggFP+68I4chLZV2yIKsXJFNZ+eWh6s=
@@ -24,19 +22,14 @@ github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZN
 github.com/rivo/uniseg v0.1.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.2.0 h1:S1pD9weZBuJdFmowNwbpi7BJ8TNftyUImj/0WQi72jY=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
-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 v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
+golang.org/x/exp v0.0.0-20231006140011-7918f672742d h1:jtJma62tbqLibJ5sFQz8bKtEM8rJBtfilJ2qTU199MI=
+golang.org/x/exp v0.0.0-20231006140011-7918f672742d/go.mod h1:ldy0pHrwJyGW56pPQzzkH36rKxoZW1tw7ZJpeKx+hdo=
 golang.org/x/sys v0.6.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.7.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.12.0 h1:CM0HF96J0hcLAwsHPJZjfdNzs0gftsLfgKt57wWHJ0o=
-golang.org/x/sys v0.12.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.13.0 h1:Af8nKPmuFypiUBjVoU9V20FiaFXOcuZI21p0ycVYYGE=
+golang.org/x/sys v0.13.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 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=

json_test.go

@@ -24,7 +24,7 @@ func TestJson(t *testing.T) {
 	}{
 		{
 			name:     "default logger info with timestamp",
-			expected: "{\"lvl\":\"info\",\"msg\":\"info\"}\n",
+			expected: "{\"level\":\"info\",\"msg\":\"info\"}\n",
 			msg:      "info",
 			kvs:      nil,
 			f:        l.Info,
@@ -38,77 +38,77 @@ func TestJson(t *testing.T) {
 		},
 		{
 			name:     "default logger error with timestamp",
-			expected: "{\"lvl\":\"error\",\"msg\":\"info\"}\n",
+			expected: "{\"level\":\"error\",\"msg\":\"info\"}\n",
 			msg:      "info",
 			kvs:      nil,
 			f:        l.Error,
 		},
 		{
 			name:     "multiline message",
-			expected: "{\"lvl\":\"error\",\"msg\":\"info\\ninfo\"}\n",
+			expected: "{\"level\":\"error\",\"msg\":\"info\\ninfo\"}\n",
 			msg:      "info\ninfo",
 			kvs:      nil,
 			f:        l.Error,
 		},
 		{
 			name:     "multiline kvs",
-			expected: "{\"lvl\":\"error\",\"msg\":\"info\",\"multiline\":\"info\\ninfo\"}\n",
+			expected: "{\"level\":\"error\",\"msg\":\"info\",\"multiline\":\"info\\ninfo\"}\n",
 			msg:      "info",
 			kvs:      []interface{}{"multiline", "info\ninfo"},
 			f:        l.Error,
 		},
 		{
 			name:     "odd number of kvs",
-			expected: "{\"baz\":\"missing value\",\"foo\":\"bar\",\"lvl\":\"error\",\"msg\":\"info\"}\n",
+			expected: "{\"baz\":\"missing value\",\"foo\":\"bar\",\"level\":\"error\",\"msg\":\"info\"}\n",
 			msg:      "info",
 			kvs:      []interface{}{"foo", "bar", "baz"},
 			f:        l.Error,
 		},
 		{
 			name:     "error field",
-			expected: "{\"error\":\"error message\",\"lvl\":\"error\",\"msg\":\"info\"}\n",
+			expected: "{\"error\":\"error message\",\"level\":\"error\",\"msg\":\"info\"}\n",
 			msg:      "info",
 			kvs:      []interface{}{"error", errors.New("error message")},
 			f:        l.Error,
 		},
 		{
 			name:     "struct field",
-			expected: "{\"lvl\":\"info\",\"msg\":\"info\",\"struct\":{}}\n",
+			expected: "{\"level\":\"info\",\"msg\":\"info\",\"struct\":{}}\n",
 			msg:      "info",
 			kvs:      []interface{}{"struct", struct{ foo string }{foo: "bar"}},
 			f:        l.Info,
 		},
 		{
 			name:     "slice field",
-			expected: "{\"lvl\":\"info\",\"msg\":\"info\",\"slice\":[1,2,3]}\n",
+			expected: "{\"level\":\"info\",\"msg\":\"info\",\"slice\":[1,2,3]}\n",
 			msg:      "info",
 			kvs:      []interface{}{"slice", []int{1, 2, 3}},
 			f:        l.Info,
 		},
 		{
 			name:     "slice of structs",
-			expected: "{\"lvl\":\"info\",\"msg\":\"info\",\"slice\":[{},{}]}\n",
+			expected: "{\"level\":\"info\",\"msg\":\"info\",\"slice\":[{},{}]}\n",
 			msg:      "info",
 			kvs:      []interface{}{"slice", []struct{ foo string }{{foo: "bar"}, {foo: "baz"}}},
 			f:        l.Info,
 		},
 		{
 			name:     "slice of strings",
-			expected: "{\"lvl\":\"info\",\"msg\":\"info\",\"slice\":[\"foo\",\"bar\"]}\n",
+			expected: "{\"level\":\"info\",\"msg\":\"info\",\"slice\":[\"foo\",\"bar\"]}\n",
 			msg:      "info",
 			kvs:      []interface{}{"slice", []string{"foo", "bar"}},
 			f:        l.Info,
 		},
 		{
 			name:     "slice of errors",
-			expected: "{\"lvl\":\"info\",\"msg\":\"info\",\"slice\":[{},{}]}\n",
+			expected: "{\"level\":\"info\",\"msg\":\"info\",\"slice\":[{},{}]}\n",
 			msg:      "info",
 			kvs:      []interface{}{"slice", []error{errors.New("error message1"), errors.New("error message2")}},
 			f:        l.Info,
 		},
 		{
 			name:     "map of strings",
-			expected: "{\"lvl\":\"info\",\"map\":{\"a\":\"b\",\"foo\":\"bar\"},\"msg\":\"info\"}\n",
+			expected: "{\"level\":\"info\",\"map\":{\"a\":\"b\",\"foo\":\"bar\"},\"msg\":\"info\"}\n",
 			msg:      "info",
 			kvs:      []interface{}{"map", map[string]string{"a": "b", "foo": "bar"}},
 			f:        l.Info,
@@ -140,14 +140,14 @@ func TestJsonCaller(t *testing.T) {
 	}{
 		{
 			name:     "simple caller",
-			expected: fmt.Sprintf("{\"caller\":\"log/%s:%d\",\"lvl\":\"info\",\"msg\":\"info\"}\n", filepath.Base(file), line+30),
+			expected: fmt.Sprintf("{\"caller\":\"log/%s:%d\",\"level\":\"info\",\"msg\":\"info\"}\n", filepath.Base(file), line+30),
 			msg:      "info",
 			kvs:      nil,
 			f:        l.Info,
 		},
 		{
 			name:     "nested caller",
-			expected: fmt.Sprintf("{\"caller\":\"log/%s:%d\",\"lvl\":\"info\",\"msg\":\"info\"}\n", filepath.Base(file), line+30),
+			expected: fmt.Sprintf("{\"caller\":\"log/%s:%d\",\"level\":\"info\",\"msg\":\"info\"}\n", filepath.Base(file), line+30),
 			msg:      "info",
 			kvs:      nil,
 			f: func(msg interface{}, kvs ...interface{}) {
@@ -177,5 +177,5 @@ func TestJsonCustomKey(t *testing.T) {
 	logger.SetFormatter(JSONFormatter)
 	logger.SetReportTimestamp(true)
 	logger.Info("info")
-	require.Equal(t, "{\"lvl\":\"info\",\"msg\":\"info\",\"time\":\"0001/01/01 00:00:00\"}\n", buf.String())
+	require.Equal(t, "{\"level\":\"info\",\"msg\":\"info\",\"time\":\"0002/01/01 00:00:00\"}\n", buf.String())
 }

level.go

@@ -3,6 +3,7 @@ package log
 import (
 	"errors"
 	"fmt"
+	"math"
 	"strings"
 )
 
@@ -11,17 +12,17 @@ type Level int32
 
 const (
 	// DebugLevel is the debug level.
-	DebugLevel Level = iota - 1
+	DebugLevel Level = -4
 	// InfoLevel is the info level.
-	InfoLevel
+	InfoLevel Level = 0
 	// WarnLevel is the warn level.
-	WarnLevel
+	WarnLevel Level = 4
 	// ErrorLevel is the error level.
-	ErrorLevel
+	ErrorLevel Level = 8
 	// FatalLevel is the fatal level.
-	FatalLevel
+	FatalLevel Level = 12
 	// noLevel is used with log.Print.
-	noLevel
+	noLevel Level = math.MaxInt32
 )
 
 // String returns the string representation of the level.

level_121.go

@@ -0,0 +1,15 @@
+//go:build go1.21
+// +build go1.21
+
+package log
+
+import "log/slog"
+
+// fromSlogLevel converts slog.Level to log.Level.
+var fromSlogLevel = map[slog.Level]Level{
+	slog.LevelDebug: DebugLevel,
+	slog.LevelInfo:  InfoLevel,
+	slog.LevelWarn:  WarnLevel,
+	slog.LevelError: ErrorLevel,
+	slog.Level(12):  FatalLevel,
+}

level_no121.go

@@ -0,0 +1,15 @@
+//go:build !go1.21
+// +build !go1.21
+
+package log
+
+import "golang.org/x/exp/slog"
+
+// fromSlogLevel converts slog.Level to log.Level.
+var fromSlogLevel = map[slog.Level]Level{
+	slog.LevelDebug: DebugLevel,
+	slog.LevelInfo:  InfoLevel,
+	slog.LevelWarn:  WarnLevel,
+	slog.LevelError: ErrorLevel,
+	slog.Level(12):  FatalLevel,
+}