v2: Logging! (#2831)

* logging: Initial implementation

* logging: More encoder formats, better defaults

* logging: Fix repetition bug with FilterEncoder; add more presets

* logging: DiscardWriter; delete or no-op logs that discard their output

* logging: Add http.handlers.log module; enhance Replacer methods

The Replacer interface has new methods to customize how to handle empty
or unrecognized placeholders. Closes #2815.

* logging: Overhaul HTTP logging, fix bugs, improve filtering, etc.

* logging: General cleanup, begin transitioning to using new loggers

* Fixes after merge conflict

modules/logging/nopencoder.go

@@ -0,0 +1,114 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package logging
+
+import (
+	"time"
+
+	"go.uber.org/zap/buffer"
+	"go.uber.org/zap/zapcore"
+)
+
+// nopEncoder is a zapcore.Encoder that does nothing.
+type nopEncoder struct{}
+
+// AddArray is part of the zapcore.ObjectEncoder interface.
+// Array elements do not get filtered.
+func (nopEncoder) AddArray(key string, marshaler zapcore.ArrayMarshaler) error { return nil }
+
+// AddObject is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddObject(key string, marshaler zapcore.ObjectMarshaler) error { return nil }
+
+// AddBinary is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddBinary(key string, value []byte) {}
+
+// AddByteString is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddByteString(key string, value []byte) {}
+
+// AddBool is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddBool(key string, value bool) {}
+
+// AddComplex128 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddComplex128(key string, value complex128) {}
+
+// AddComplex64 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddComplex64(key string, value complex64) {}
+
+// AddDuration is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddDuration(key string, value time.Duration) {}
+
+// AddFloat64 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddFloat64(key string, value float64) {}
+
+// AddFloat32 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddFloat32(key string, value float32) {}
+
+// AddInt is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddInt(key string, value int) {}
+
+// AddInt64 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddInt64(key string, value int64) {}
+
+// AddInt32 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddInt32(key string, value int32) {}
+
+// AddInt16 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddInt16(key string, value int16) {}
+
+// AddInt8 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddInt8(key string, value int8) {}
+
+// AddString is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddString(key, value string) {}
+
+// AddTime is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddTime(key string, value time.Time) {}
+
+// AddUint is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddUint(key string, value uint) {}
+
+// AddUint64 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddUint64(key string, value uint64) {}
+
+// AddUint32 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddUint32(key string, value uint32) {}
+
+// AddUint16 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddUint16(key string, value uint16) {}
+
+// AddUint8 is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddUint8(key string, value uint8) {}
+
+// AddUintptr is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddUintptr(key string, value uintptr) {}
+
+// AddReflected is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) AddReflected(key string, value interface{}) error { return nil }
+
+// OpenNamespace is part of the zapcore.ObjectEncoder interface.
+func (nopEncoder) OpenNamespace(key string) {}
+
+// Clone is part of the zapcore.ObjectEncoder interface.
+// We don't use it as of Oct 2019 (v2 beta 7), I'm not
+// really sure what it'd be useful for in our case.
+func (ne nopEncoder) Clone() zapcore.Encoder { return ne }
+
+// EncodeEntry partially implements the zapcore.Encoder interface.
+func (nopEncoder) EncodeEntry(ent zapcore.Entry, fields []zapcore.Field) (*buffer.Buffer, error) {
+	return bufferpool.Get(), nil
+}
+
+// Interface guard
+var _ zapcore.Encoder = (*nopEncoder)(nil)