125 lines
3.7 KiB
Markdown
125 lines
3.7 KiB
Markdown
# `tint`: 🌈 **slog.Handler** that writes tinted logs
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[](https://pkg.go.dev/github.com/lmittmann/tint#section-documentation)
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[](https://goreportcard.com/report/github.com/lmittmann/tint)
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<picture>
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<source media="(prefers-color-scheme: dark)" srcset="https://github.com/lmittmann/tint/assets/3458786/3d42f8d5-8bdf-40db-a16a-1939c88689cb">
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<source media="(prefers-color-scheme: light)" srcset="https://github.com/lmittmann/tint/assets/3458786/3d42f8d5-8bdf-40db-a16a-1939c88689cb">
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<img src="https://github.com/lmittmann/tint/assets/3458786/3d42f8d5-8bdf-40db-a16a-1939c88689cb">
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</picture>
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<br>
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<br>
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Package `tint` implements a zero-dependency [`slog.Handler`](https://pkg.go.dev/log/slog#Handler)
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that writes tinted (colorized) logs. Its output format is inspired by the `zerolog.ConsoleWriter` and
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[`slog.TextHandler`](https://pkg.go.dev/log/slog#TextHandler).
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The output format can be customized using [`Options`](https://pkg.go.dev/github.com/lmittmann/tint#Options)
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which is a drop-in replacement for [`slog.HandlerOptions`](https://pkg.go.dev/log/slog#HandlerOptions).
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```
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go get github.com/lmittmann/tint
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```
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## Usage
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```go
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w := os.Stderr
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// Create a new logger
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logger := slog.New(tint.NewHandler(w, nil))
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// Set global logger with custom options
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slog.SetDefault(slog.New(
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tint.NewHandler(w, &tint.Options{
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Level: slog.LevelDebug,
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TimeFormat: time.Kitchen,
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}),
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))
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```
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### Customize Attributes
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`ReplaceAttr` can be used to alter or drop attributes. If set, it is called on
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each non-group attribute before it is logged. See [`slog.HandlerOptions`](https://pkg.go.dev/log/slog#HandlerOptions)
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for details.
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```go
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// Create a new logger with a custom TRACE level:
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const LevelTrace = slog.LevelDebug - 4
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w := os.Stderr
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logger := slog.New(tint.NewHandler(w, &tint.Options{
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Level: LevelTrace,
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ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
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if a.Key == slog.LevelKey && len(groups) == 0 {
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level, ok := a.Value.Any().(slog.Level)
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if ok && level <= LevelTrace {
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return tint.Attr(13, slog.String(a.Key, "TRC"))
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}
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}
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return a
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},
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}))
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```
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```go
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// Create a new logger that doesn't write the time
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w := os.Stderr
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logger := slog.New(
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tint.NewHandler(w, &tint.Options{
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ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
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if a.Key == slog.TimeKey && len(groups) == 0 {
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return slog.Attr{}
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}
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return a
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},
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}),
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)
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```
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```go
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// Create a new logger that writes all errors in red
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w := os.Stderr
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logger := slog.New(
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tint.NewHandler(w, &tint.Options{
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ReplaceAttr: func(groups []string, a slog.Attr) slog.Attr {
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if a.Value.Kind() == slog.KindAny {
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if _, ok := a.Value.Any().(error); ok {
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return tint.Attr(9, a)
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}
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}
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return a
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},
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}),
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)
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```
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### Automatically Enable Colors
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Colors are enabled by default. Use the `Options.NoColor` field to disable
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color output. To automatically enable colors based on terminal capabilities, use
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e.g., the [`go-isatty`](https://github.com/mattn/go-isatty) package:
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```go
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w := os.Stderr
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logger := slog.New(
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tint.NewHandler(w, &tint.Options{
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NoColor: !isatty.IsTerminal(w.Fd()),
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}),
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)
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```
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### Windows Support
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Color support on Windows can be added by using e.g., the
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[`go-colorable`](https://github.com/mattn/go-colorable) package:
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```go
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w := os.Stderr
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logger := slog.New(
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tint.NewHandler(colorable.NewColorable(w), nil),
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)
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```
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