| // 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" |
| "os" |
| |
| "golang.org/x/exp/slog" |
| "golang.org/x/exp/slog/internal/testutil" |
| ) |
| |
| // 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() { |
| th := slog.NewTextHandler(os.Stdout, &slog.HandlerOptions{ReplaceAttr: testutil.RemoveTime}) |
| logger := slog.New(NewLevelHandler(slog.LevelWarn, th)) |
| logger.Info("not printed") |
| logger.Warn("printed") |
| |
| // Output: |
| // level=WARN msg=printed |
| } |