Encoders should fall back to default Encode* implementations

[dxvgef]

package main

import (
    "time"

    "go.uber.org/zap"
    "go.uber.org/zap/zapcore"
)

var Logger *zap.Logger

func main() {
    err := setLogger()
    if err != nil {
        println(err.Error())
        return
    }
    defer Logger.Sync()
    Logger.Debug("test")
}

func setLogger() (err error) {
    encodeConfig := zapcore.EncoderConfig{
        MessageKey: "message",
        LevelKey:   "level",
        TimeKey:    "time",
        NameKey:    "name",
        CallerKey:  "file",
        EncodeTime: timeEncoder,
    }
    config := zap.Config{
        Level:         zap.NewAtomicLevelAt(zapcore.DebugLevel),
        Development:   false,
        Encoding:      "json",
        EncoderConfig: encodeConfig,
        OutputPaths:   []string{"stderr"},
    }
    Logger, err = config.Build()
    return
}

func timeEncoder(t time.Time, enc zapcore.PrimitiveArrayEncoder) {
    enc.AppendString(t.Format("2006-01-02 15:04:05"))
}

It's normal to change "Encoding" to "console"

[billf]

zapcore.EncoderConfig requires an encoder for the keys you've specified. encodeConfig.LevelKey is set but encodeConfig.EncodeLevel is not.

https://godoc.org/go.uber.org/zap/zapcore#EncoderConfig

You can use the system defaults for the rest of the encoders:

        EncodeLevel:    zapcore.LowercaseLevelEncoder,
        EncodeDuration: zapcore.SecondsDurationEncoder,
        EncodeCaller:   zapcore.ShortCallerEncoder,

It's possibly a bug that Config.Build does not error here.

[akshayjshah]

I went back and forth on this, and at the time settled on forcing users of this API to be explicit about the behavior they'd prefer.

We could make config.Build error here, or we could make zapcore.NewJSONEncoder and zapcore.NewConsoleEncoder automatically fall back to the default encoders.