Lots of additions:

- added unit tests
- renamed to yadu
- added gh test actions
- added docs

.github/workflows/ci.yaml

@@ -0,0 +1,47 @@
+name: build-and-test
+on: [push, pull_request]
+jobs:
+  build:
+    strategy:
+      matrix:
+        version: [1.21]
+        os: [ubuntu-latest, windows-latest, macos-latest]
+    name: Build
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Set up Go
+      uses: actions/setup-go@v3
+      with:
+        go-version: ${{ matrix.version }}
+      id: go
+
+    - name: checkout
+      uses: actions/checkout@v3
+
+    - name: build
+      run: go build
+
+    - name: test
+      run: make test
+
+    - name: Update coverage report
+      uses: ncruces/go-coverage-report@main
+      with:
+        report: true
+        chart: true
+        amend: true
+      if: |
+        matrix.os == 'ubuntu-latest' &&
+        github.event_name == 'push'  
+      continue-on-error: true
+  
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/setup-go@v3
+        with:
+          go-version: 1.21
+      - uses: actions/checkout@v3
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v3

.gitignore

@@ -0,0 +1 @@
+coverage.out

Makefile

@@ -0,0 +1,32 @@
+# Copyright © 2023 Thomas von Dein
+
+# This  module  is published  under  the  terms  of the  BSD  3-Clause
+# License. Please read the file LICENSE for details.
+
+#
+# no need to modify anything below
+
+all: buildlocal
+
+buildlocal:
+	go build
+
+clean:
+	rm -rf $(tool) coverage.out testdata t/out
+
+test: clean
+	go test $(ARGS)
+
+singletest:
+	@echo "Call like this: make singletest TEST=TestPrepareColumns ARGS=-v"
+	go test -run $(TEST) $(ARGS)
+
+cover-report:
+	go test -cover -coverprofile=coverage.out
+	go tool cover -html=coverage.out
+
+goupdate:
+	go get -t -u=patch ./...
+
+lint:
+	golangci-lint run -p bugs -p unused

README.md

@@ -1,6 +1,48 @@
-# YamlDumpHandler - a human readable yaml based slog.Handler
+[![Go Report Card](https://goreportcard.com/badge/github.com/tlinden/yadu)](https://goreportcard.com/report/github.com/tlinden/yadu) 
+[![Actions](https://github.com/tlinden/yadu/actions/workflows/ci.yaml/badge.svg)](https://github.com/tlinden/yadu/actions)
+[![Go Coverage](https://github.com/tlinden/yadu/wiki/coverage.svg)](https://raw.githack.com/wiki/tlinden/yadu/coverage.html)
+![GitHub License](https://img.shields.io/github/license/tlinden/yadu)
 
-Example output:
+# yadu - a human readable yaml based slog.Handler
+
+## Introduction
+
+Package yadu provides a handler for the log/slog logging framework.
+
+It generates a  mixture of text lines containing  the timestamp and
+log message and a YAML dump of the provided attibutes.
+
+## Log format
+
+The log format generated by yadu looks like this:
+
+```
+2023-04-02T10:50.09 EDT LEVEL Message text
+    foo: value
+    bar: 12345
+```
+
+## Example
+
+```go
+logger := slog.New(yadu.NewHandler(os.Stdout, nil))
+
+type Enemy struct {
+    Alive  bool
+    Health int
+    Name   string
+    Body   body `yaml:"-"` // not printed
+    Ammo   []Ammo
+}
+
+e := &Enemy{Alive: true, Health: 10, Name: "Bodo", Body: "body\nbody\n",
+    Ammo: []Ammo{{Forweapon: "Railgun", Range: 400, Impact: 100, Cost: 100000}},
+}
+
+slog.Info("info", "enemy", e, "spawn", 199)
+```
+
+Output:
 
 ```sh
 2024-01-18T02:57.41 CET INFO: info 
@@ -14,12 +56,76 @@ Example output:
               cost: 100000
               range: 400
     spawn: 199
-2024-01-18T02:57.41 CET INFO: connecting 
-    enemies: 100
-    players: 2
-    world: 600x800
-2024-01-18T02:57.41 CET DEBUG: debug text 
-2024-01-18T02:57.41 CET ERROR: error 
 ```
 
-See `example.go` for usage.
+See `example/example.go` for usage.
+
+## Installation
+
+Execute this to add the module to your project:
+```sh
+go get github.com/tlinden/yadu
+```
+
+## Configuration
+
+You can tweak the behavior of the handler as any other handler by using the Options struct:
+
+```go
+func removeTime(_ []string, a slog.Attr) slog.Attr {
+        if a.Key == slog.TimeKey {
+                return slog.Attr{}
+        }
+        return a
+}
+
+opts := &yadu.Options{
+           Level: slog.LevelDebug,
+           ReplaceAttr: removeTime,
+        }
+```
+
+Pass this object to `yadu.NewHandler()`.
+
+Because you can pass whole structs  to the logger which will be dumped
+using YAML, there's also a way to exclude fields from being printed:
+
+```go
+type User struct {
+  Id int
+  User string
+  Pass string `yaml:"-"`
+}
+```
+
+If you're already using YAML tags for other purposes you can also just
+add a  `LogValue()` method  to your  struct, which  will be  called by
+slog. Refer to the slog documentation how to use it.
+
+You can also modify the time format using `yadu.Options.TimeFormat`.
+
+## Acknowledgements
+
+I  wrote  most  of  the  code  with  the  help  of  the  [humane  slog
+handler][humane]. Also helpfull was the  [guide to writing `slog` handlers][guide].
+
++ [humane slog handler][humane]
++ [A Guide to Writing `slog` Handlers][guide]
++ [`slog`: Golang's official structured logging package][sobyte]
++ [A Comprehensive Guide to Structured Logging in Go][betterstack]
+
+[humane]: https://github.com/telemachus/humane/tree/main
+[guide]: https://github.com/golang/example/tree/master/slog-handler-guide
+[mrkaran]: https://mrkaran.dev/posts/structured-logging-in-go-with-slog/
+[betterstack]: https://betterstack.com/community/guides/logging/logging-in-go/
+
+
+## LICENSE
+
+This  module  is  published  under  the  terms  of  the  BSD  3-Clause
+License. Please read the file LICENSE for details.
+
+## Author
+
+Thomas von Dein `<git |AT| daemon.de>`
+

go.mod

@@ -1,4 +1,4 @@
-module github.com/tlinden/yamldumphandler
+module github.com/tlinden/yadu
 
 go 1.21
 

handler.go

@@ -1,4 +1,4 @@
-package yamldumphandler
+package yadu
 
 import (
 	"bytes"
@@ -15,9 +15,13 @@ import (
 	"github.com/fatih/color"
 )
 
-const defaultTimeFormat = "2006-01-02T03:04.05 MST"
+// We use RFC datestring by default
+const DefaultTimeFormat = "2006-01-02T03:04.05 MST"
 
-type YamlDumpHandler struct {
+// Default log level is INFO:
+const defaultLevel = slog.LevelInfo
+
+type Handler struct {
 	writer      io.Writer
 	mu          *sync.Mutex
 	level       slog.Leveler
@@ -29,14 +33,25 @@ type YamlDumpHandler struct {
 	indenter    *regexp.Regexp
 }
 
-type YamlDumpHandlerOptions struct {
+// Options are options for the Yadu [log/slog.Handler].
+//
+// Level sets the minimum log level.
+//
+// ReplaceAttr is a function you  can define to customize how supplied
+// attrs are being handled. It is empty by default, so nothing will be
+// altered.
+//
+// Loglevel and message cannot be altered using ReplaceAttr. Timestamp
+// can only be removed, see example. Keep in mind that everything will
+// be passed to yaml.Marshal() in the end.
+type Options struct {
 	Level       slog.Leveler
 	ReplaceAttr func(groups []string, a slog.Attr) slog.Attr
 	TimeFormat  string
 	AddSource   bool
 }
 
-func (h *YamlDumpHandler) Handle(ctx context.Context, r slog.Record) error {
+func (h *Handler) Handle(ctx context.Context, r slog.Record) error {
 	level := r.Level.String() + ":"
 
 	switch r.Level {
@@ -97,21 +112,21 @@ func (h *YamlDumpHandler) Handle(ctx context.Context, r slog.Record) error {
 	defer h.mu.Unlock()
 	_, err := h.writer.Write(buf.Bytes())
 
-	//	h.l.Println(timeStr, level, msg, color.WhiteString(tree))
-
 	return err
 }
 
-func (h *YamlDumpHandler) Postprocess(yamlstr []byte) string {
+func (h *Handler) Postprocess(yamlstr []byte) string {
 	return "\n    " + strings.TrimSpace(h.indenter.ReplaceAllString(string(yamlstr), "    "))
 }
 
-func NewYamlDumpHandler(out io.Writer, opts *YamlDumpHandlerOptions) *YamlDumpHandler {
+// NewHandler returns a [log/slog.Handler] using the receiver's options.
+// Default options are used if opts is nil.
+func NewHandler(out io.Writer, opts *Options) *Handler {
 	if opts == nil {
-		opts = &YamlDumpHandlerOptions{}
+		opts = &Options{}
 	}
 
-	h := &YamlDumpHandler{
+	h := &Handler{
 		writer:      out,
 		mu:          &sync.Mutex{},
 		level:       opts.Level,
@@ -121,20 +136,24 @@ func NewYamlDumpHandler(out io.Writer, opts *YamlDumpHandlerOptions) *YamlDumpHa
 		indenter:    regexp.MustCompile(`(?m)^`),
 	}
 
+	if opts.Level == nil {
+		h.level = defaultLevel
+	}
+
 	if h.timeFormat == "" {
-		h.timeFormat = defaultTimeFormat
+		h.timeFormat = DefaultTimeFormat
 	}
 
 	return h
 }
 
 // Enabled indicates whether the receiver logs at the given level.
-func (h *YamlDumpHandler) Enabled(_ context.Context, l slog.Level) bool {
+func (h *Handler) Enabled(_ context.Context, l slog.Level) bool {
 	return l >= h.level.Level()
 }
 
 // attributes plus attrs.
-func (h *YamlDumpHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+func (h *Handler) WithAttrs(attrs []slog.Attr) slog.Handler {
 	if len(attrs) == 0 {
 		return h
 	}
@@ -157,7 +176,7 @@ func (h *YamlDumpHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
 
 // WithGroup returns a new [log/slog.Handler] with name appended to the
 // receiver's groups.
-func (h *YamlDumpHandler) WithGroup(name string) slog.Handler {
+func (h *Handler) WithGroup(name string) slog.Handler {
 	if name == "" {
 		return h
 	}
@@ -166,8 +185,8 @@ func (h *YamlDumpHandler) WithGroup(name string) slog.Handler {
 	return h2
 }
 
-func (h *YamlDumpHandler) clone() *YamlDumpHandler {
+func (h *Handler) clone() *Handler {
-	return &YamlDumpHandler{
+	return &Handler{
 		writer:      h.writer,
 		mu:          h.mu,
 		level:       h.level,

handler_test.go

@@ -0,0 +1,115 @@
+package yadu_test
+
+import (
+	"bytes"
+	"log/slog"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/tlinden/yadu"
+)
+
+type body string
+
+type Ammo struct {
+	Forweapon string
+	Impact    int
+	Cost      int
+	Range     float32
+}
+
+type Enemy struct {
+	Alive  bool
+	Health int
+	Name   string
+	Body   body `yaml:"-"`
+	Ammo   []Ammo
+}
+
+type Tests struct {
+	name   string
+	want   string
+	negate bool
+	opts   *yadu.Options
+}
+
+const testTimeFormat = "03:04.05"
+
+var tests = []Tests{
+	{
+		name:   "has-railgun",
+		want:   "forweapon: Railgun",
+		negate: false,
+	},
+	{
+		name:   "has-ammo",
+		want:   "ammo:",
+		negate: false,
+	},
+	{
+		name:   "has-alive",
+		want:   "alive: true",
+		negate: false,
+	},
+	{
+		name:   "has-no-body",
+		want:   "body:",
+		negate: true,
+	},
+	{
+		name:   "has-time",
+		want:   time.Now().Format(yadu.DefaultTimeFormat),
+		negate: false,
+	},
+	{
+		name: "has-no-time",
+		want: time.Now().Format(yadu.DefaultTimeFormat),
+		opts: &yadu.Options{
+			ReplaceAttr: removeTime,
+		},
+		negate: true,
+	},
+	{
+		name: "has-custom-time",
+		want: time.Now().Format(testTimeFormat),
+		opts: &yadu.Options{
+			TimeFormat: testTimeFormat,
+		},
+		negate: false,
+	},
+	// FIXME: add WithGroup + WithAttr tests
+}
+
+func GetEnemy() *Enemy {
+	return &Enemy{Alive: true, Health: 10, Name: "Bodo", Body: "body\nbody\n",
+		Ammo: []Ammo{{Forweapon: "Railgun", Range: 400, Impact: 100, Cost: 100000}},
+	}
+
+}
+
+func removeTime(_ []string, a slog.Attr) slog.Attr {
+	if a.Key == slog.TimeKey {
+		return slog.Attr{}
+	}
+	return a
+}
+
+func Test(t *testing.T) {
+	t.Parallel()
+
+	for _, tt := range tests {
+		var buf bytes.Buffer
+
+		logger := slog.New(yadu.NewHandler(&buf, tt.opts))
+
+		logger.Info("attack", "enemy", GetEnemy())
+		got := buf.String()
+
+		if strings.Contains(got, tt.want) == tt.negate {
+			t.Errorf("test %s failed.\n want:\n%s\n got: %s\n", tt.name, tt.want, got)
+		}
+
+		buf.Reset()
+	}
+}