MM-11029 Adding plugin logging functionality. (#9034)

* Capturing stdout, stderr of plugins in logs.

* Cleanup go-plugin debug logs.

* Adding logging to plugin API

* Generating mocks.

* godoc convention

4 files changed, 71 insertions, 3 deletions

diff --git a/mlog/global.go b/mlog/global.go
index 36dd51afb..ba90ace2f 100644
--- a/mlog/global.go
+++ b/mlog/global.go
@@ -11,7 +11,9 @@ import (
 var globalLogger *Logger
 
 func InitGlobalLogger(logger *Logger) {
-	globalLogger = logger
+	glob := *logger
+	glob.zap = glob.zap.WithOptions(zap.AddCallerSkip(1))
+	globalLogger = &glob
 	Debug = globalLogger.Debug
 	Info = globalLogger.Info
 	Warn = globalLogger.Warn
@@ -20,7 +22,7 @@ func InitGlobalLogger(logger *Logger) {
 }
 
 func RedirectStdLog(logger *Logger) {
-	zap.RedirectStdLogAt(logger.zap.With(zap.String("source", "stdlog")), zapcore.ErrorLevel)
+	zap.RedirectStdLogAt(logger.zap.With(zap.String("source", "stdlog")).WithOptions(zap.AddCallerSkip(-2)), zapcore.ErrorLevel)
 }
 
 type LogFunc func(string, ...Field)
diff --git a/mlog/log.go b/mlog/log.go
index 780e1ad57..e3bc38d83 100644
--- a/mlog/log.go
+++ b/mlog/log.go
@@ -4,6 +4,7 @@
 package mlog
 
 import (
+	"io"
 	"log"
 	"os"
 
@@ -101,7 +102,7 @@ func NewLogger(config *LoggerConfiguration) *Logger {
 	combinedCore := zapcore.NewTee(cores...)
 
 	logger.zap = zap.New(combinedCore,
-		zap.AddCallerSkip(2),
+		zap.AddCallerSkip(1),
 		zap.AddCaller(),
 	)
 
@@ -127,6 +128,30 @@ func (l *Logger) StdLog(fields ...Field) *log.Logger {
 	return zap.NewStdLog(l.With(fields...).zap.WithOptions(getStdLogOption()))
 }
 
+// StdLogWriter returns a writer that can be hooked up to the output of a golang standard logger
+// anything written will be interpreted as log entries accordingly
+func (l *Logger) StdLogWriter() io.Writer {
+	newLogger := *l
+	newLogger.zap = newLogger.zap.WithOptions(zap.AddCallerSkip(4), getStdLogOption())
+	f := newLogger.Info
+	return &loggerWriter{f}
+}
+
+func (l *Logger) WithCallerSkip(skip int) *Logger {
+	newlogger := *l
+	newlogger.zap = newlogger.zap.WithOptions(zap.AddCallerSkip(skip))
+	return &newlogger
+}
+
+// Made for the plugin interface, wraps mlog in a simpler interface
+// at the cost of performance
+func (l *Logger) Sugar() *SugarLogger {
+	return &SugarLogger{
+		wrappedLogger: l,
+		zapSugar:      l.zap.Sugar(),
+	}
+}
+
 func (l *Logger) Debug(message string, fields ...Field) {
 	l.zap.Debug(message, fields...)
 }
diff --git a/mlog/stdlog.go b/mlog/stdlog.go
index a875b2e32..7839ddfa0 100644
--- a/mlog/stdlog.go
+++ b/mlog/stdlog.go
@@ -4,6 +4,7 @@
 package mlog
 
 import (
+	"bytes"
 	"strings"
 
 	"go.uber.org/zap"
@@ -72,3 +73,15 @@ func getStdLogOption() zap.Option {
 		},
 	)
 }
+
+type loggerWriter struct {
+	logFunc func(msg string, fields ...Field)
+}
+
+func (l *loggerWriter) Write(p []byte) (int, error) {
+	trimmed := string(bytes.TrimSpace(p))
+	for _, line := range strings.Split(trimmed, "\n") {
+		l.logFunc(string(line))
+	}
+	return len(p), nil
+}
diff --git a/mlog/sugar.go b/mlog/sugar.go
new file mode 100644
index 000000000..c00a8bbfc
--- /dev/null
+++ b/mlog/sugar.go
@@ -0,0 +1,28 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package mlog
+
+import "go.uber.org/zap"
+
+// Made for the plugin interface, use the regular logger for other uses
+type SugarLogger struct {
+	wrappedLogger *Logger
+	zapSugar      *zap.SugaredLogger
+}
+
+func (l *SugarLogger) Debug(msg string, keyValuePairs ...interface{}) {
+	l.zapSugar.Debugw(msg, keyValuePairs...)
+}
+
+func (l *SugarLogger) Info(msg string, keyValuePairs ...interface{}) {
+	l.zapSugar.Infow(msg, keyValuePairs...)
+}
+
+func (l *SugarLogger) Error(msg string, keyValuePairs ...interface{}) {
+	l.zapSugar.Errorw(msg, keyValuePairs...)
+}
+
+func (l *SugarLogger) Warn(msg string, keyValuePairs ...interface{}) {
+	l.zapSugar.Warnw(msg, keyValuePairs...)
+}