go: infra/libs/* now live in luci-go.

go/src/infra/libs/logging/logging.go

-// Copyright 2014 The Chromium 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 logging defines Logger interface and context.Context helpers to put\get
-logger from context.Context.
-
-Unfortunately standard library doesn't define any Logger interface (only
-struct). And even worse: GAE logger is exposing different set of methods. Some
-additional layer is needed to unify the logging. Package logging is intended to
-be used from packages that support both local and GAE environments. Such
-packages should not use global logger but must accept instances of Logger
-interface (or even more generally context.Context) as parameters. Then callers
-can pass appropriate Logger implementation  (or inject appropriate logger into
-context.Context) depending on where the code is running.
-
-Libraries under infra/libs/* MUST use infra/libs/logger instead of directly
-instantiating concrete implementations.
-*/
-package logging
-
-import (
-        "golang.org/x/net/context"
-)
-
-// Logger interface is ultimately implemented by underlying logging libraries
-// (like go-logging or GAE logging). It is the least common denominator among
-// logger implementations.
-type Logger interface {
-        // Infof formats its arguments according to the format, analogous to
-        // fmt.Printf and records the text as a log message at Info level.
-        Infof(format string, args ...interface{})
-
-        // Warningf is like Infof, but logs at Warning level.
-        Warningf(format string, args ...interface{})
-
-        // Errorf is like Infof, but logs at Error level.
-        Errorf(format string, args ...interface{})
-}
-
-type key int
-
-var loggerKey key
-
-// Set sets the Logger factory for this context.
-//
-// The current Logger can be retrieved with Get(context)
-func Set(c context.Context, f func(context.Context) Logger) context.Context {
-        return context.WithValue(c, loggerKey, f)
-}
-
-// Get the current Logger, or a logger that ignores all messages if none
-// is defined.
-func Get(c context.Context) (ret Logger) {
-        if f, ok := c.Value(loggerKey).(func(context.Context) Logger); ok {
-                ret = f(c)
-        }
-        if ret == nil {
-                ret = Null()
-        }
-        return
-}
-
-// Null returns logger that silently ignores all messages.
-func Null() Logger {
-        return nullLogger{}
-}
-
-// nullLogger silently ignores all messages.
-type nullLogger struct{}
-
-func (nullLogger) Infof(string, ...interface{})    {}
-func (nullLogger) Warningf(string, ...interface{}) {}
-func (nullLogger) Errorf(string, ...interface{})   {}