File size: 2,341 Bytes
e36aeda | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 | // Copyright 2022 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package slog_test
import (
"context"
"log/slog"
"os"
)
// A LevelHandler wraps a Handler with an Enabled method
// that returns false for levels below a minimum.
type LevelHandler struct {
level slog.Leveler
handler slog.Handler
}
// NewLevelHandler returns a LevelHandler with the given level.
// All methods except Enabled delegate to h.
func NewLevelHandler(level slog.Leveler, h slog.Handler) *LevelHandler {
// Optimization: avoid chains of LevelHandlers.
if lh, ok := h.(*LevelHandler); ok {
h = lh.Handler()
}
return &LevelHandler{level, h}
}
// Enabled implements Handler.Enabled by reporting whether
// level is at least as large as h's level.
func (h *LevelHandler) Enabled(_ context.Context, level slog.Level) bool {
return level >= h.level.Level()
}
// Handle implements Handler.Handle.
func (h *LevelHandler) Handle(ctx context.Context, r slog.Record) error {
return h.handler.Handle(ctx, r)
}
// WithAttrs implements Handler.WithAttrs.
func (h *LevelHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
return NewLevelHandler(h.level, h.handler.WithAttrs(attrs))
}
// WithGroup implements Handler.WithGroup.
func (h *LevelHandler) WithGroup(name string) slog.Handler {
return NewLevelHandler(h.level, h.handler.WithGroup(name))
}
// Handler returns the Handler wrapped by h.
func (h *LevelHandler) Handler() slog.Handler {
return h.handler
}
// This example shows how to Use a LevelHandler to change the level of an
// existing Handler while preserving its other behavior.
//
// This example demonstrates increasing the log level to reduce a logger's
// output.
//
// Another typical use would be to decrease the log level (to LevelDebug, say)
// during a part of the program that was suspected of containing a bug.
func ExampleHandler_levelHandler() {
removeTime := func(groups []string, a slog.Attr) slog.Attr {
if a.Key == slog.TimeKey && len(groups) == 0 {
return slog.Attr{}
}
return a
}
th := slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{ReplaceAttr: removeTime})
logger := slog.New(NewLevelHandler(slog.LevelWarn, th))
logger.Info("not printed")
logger.Warn("printed")
// Output:
// level=WARN msg=printed
}
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