example_test.go

package slogx_test

import (
	"bytes"
	"context"
	"fmt"
	"log/slog"
	"time"

	"github.com/Arhius/slogx"
)

// ExampleNew shows the zero-configuration path: a JSON logger at info level
// writing to [os.Stdout] and installed as [slog.Default]. The example does not
// include an Output block because the emitted record carries a non-
// deterministic "time" field.
func ExampleNew() {
	lg := slogx.New(
		slogx.WithLoadFromEnv(false),
		slogx.WithSetDefault(false),
	)
	lg.Info("hello", "k", "v")
}

// ExampleNew_withLevelVar demonstrates flipping the [slog.LevelVar] threshold
// at runtime to change which records are emitted.
func ExampleNew_withLevelVar() {
	lv := &slog.LevelVar{}
	lv.Set(slog.LevelWarn)

	lg := slogx.New(
		slogx.WithLevelVar(lv),
		slogx.WithLoadFromEnv(false),
		slogx.WithSetDefault(false),
	)

	lg.Info("filtered")     // below the threshold, dropped
	lv.Set(slog.LevelDebug) // flip the threshold
	lg.Info("emitted")      // now emitted
}

// ExampleNew_withHandler shows how to plug in a caller-supplied
// [slog.Handler]. The custom handler owns its own level, format, and
// destination; LOG_* environment variables that feed the default handler are
// ignored.
func ExampleNew_withHandler() {
	buf := &bytes.Buffer{}
	h := slog.NewTextHandler(buf, &slog.HandlerOptions{Level: slog.LevelDebug})

	lg := slogx.New(
		slogx.WithHandler(h),
		slogx.WithLoadFromEnv(false),
		slogx.WithSetDefault(false),
	)

	// Emit a record with a zero time so the output is deterministic.
	r := slog.NewRecord(time.Time{}, slog.LevelDebug, "hello", 0)
	r.AddAttrs(slog.String("k", "v"))
	_ = lg.Handler().Handle(context.Background(), r)

	fmt.Print(buf.String())
	// Output: level=DEBUG msg=hello k=v
}

// ExampleNew_textFormat shows how to switch from the default JSON encoder to
// the text encoder without providing a custom handler.
func ExampleNew_textFormat() {
	buf := &bytes.Buffer{}
	lg := slogx.New(
		slogx.WithWriter(buf),
		slogx.WithFormat(slogx.TextFormat),
		slogx.WithLoadFromEnv(false),
		slogx.WithSetDefault(false),
	)

	r := slog.NewRecord(time.Time{}, slog.LevelInfo, "hello", 0)
	r.AddAttrs(slog.String("k", "v"))
	_ = lg.Handler().Handle(context.Background(), r)

	fmt.Print(buf.String())
	// Output: level=INFO msg=hello k=v
}

// ExampleNewWithLevelVar shows runtime level flipping without allocating a
// [*slog.LevelVar] up front.
func ExampleNewWithLevelVar() {
	lg, lv := slogx.NewWithLevelVar(
		slogx.WithLevel(slogx.WarnLevel),
		slogx.WithLoadFromEnv(false),
		slogx.WithSetDefault(false),
	)

	lg.Info("filtered") // below warn, dropped
	lv.Set(slog.LevelDebug)
	lg.Info("emitted")
}