Windows Event Log, error output

Adding more Event Log support, and modifying the loggers so they return
errors in their operational functions.

logging/funcs_file.go

@@ -1,61 +1,96 @@
 package logging
 
 import (
+	`errors`
 	"fmt"
 	"io"
+	`io/fs`
 	"log"
 	"os"
+	`strings`
 )
 
 // Setup sets up/configures a FileLogger and prepares it for use.
-func (l *FileLogger) Setup() {
+func (l *FileLogger) Setup() (err error) {
 
-	var err error
 	var multi io.Writer
 
-	l.Logger = log.Default()
-	l.Logger.SetPrefix(l.Prefix + " ")
-	if l.writer, err = os.OpenFile(l.Path, appendFlags, logPerm); err != nil {
-		log.Panicf("could not open log file \"%v\" for writing: %v\n", l.Path, err)
+	// This uses a shared handle across the import. We don't want that.
+	// l.Logger = log.Default()
+	if l.Prefix != "" {
+		l.Prefix = strings.TrimRight(l.Prefix, " ") + " "
+		// l.Logger.SetPrefix(l.Prefix)
 	}
+	if l.writer, err = os.OpenFile(l.Path, appendFlags, logPerm); err != nil {
+		return
+	}
+
 	// https://stackoverflow.com/a/36719588/733214
-	if l.EnableStdOut {
+	switch {
+	case l.EnableStdErr && l.EnableStdOut:
+		multi = io.MultiWriter(os.Stdout, os.Stderr, l.writer)
+	case l.EnableStdErr:
+		multi = io.MultiWriter(os.Stderr, l.writer)
+	case l.EnableStdOut:
 		multi = io.MultiWriter(os.Stdout, l.writer)
-	} else {
+	default:
 		multi = l.writer
 	}
-	l.Logger.SetOutput(multi)
+
+	l.Logger = log.New(multi, l.Prefix, l.LogFlags)
+	// l.Logger.SetOutput(multi)
+
+	return
 }
 
 // Shutdown cleanly shuts down a FileLogger.
-func (l *FileLogger) Shutdown() {
-
-	var err error
+func (l *FileLogger) Shutdown() (err error) {
 
 	if err = l.writer.Close(); err != nil {
-		log.Panicf("could not close log file \"%v\": %v\n", l.Path, err)
+		if !errors.Is(err, fs.ErrClosed) {
+			return
+		}
 	}
 
+	return
 }
 
-// GetPrefix returns the prefix used by this FileLogger.
-func (l *FileLogger) GetPrefix() string {
-	return l.Prefix
+/*
+	GetPrefix returns the prefix used by this FileLogger.
+	err will always be nil; it's there for interface-compat.
+*/
+func (l *FileLogger) GetPrefix() (prefix string, err error) {
+
+	prefix = l.Prefix
+
+	return
 }
 
 /*
 	DoDebug sets the debug state of this FileLogger.
 	Note that this merely acts as a *safety filter* for debug messages to avoid sensitive information being written to the log.
+	err will always be nil; it's there for interface-compat.
 */
-func (l *FileLogger) DoDebug(d bool) {
+func (l *FileLogger) DoDebug(d bool) (err error) {
+
 	l.EnableDebug = d
+
+	return
 }
 
-// SetPrefix sets the prefix for this FileLogger.
-func (l *FileLogger) SetPrefix(prefix string) {
+/*
+	SetPrefix sets the prefix for this FileLogger.
+	err will always be nil; it's there for interface-compat.
+*/
+func (l *FileLogger) SetPrefix(prefix string) (err error) {
 
-	l.Prefix = prefix + " "
-	l.Logger.SetPrefix(prefix + " ")
+	l.Prefix = prefix
+	if prefix != "" {
+		l.Prefix = strings.TrimRight(l.Prefix, " ") + " "
+	}
+	l.Logger.SetPrefix(l.Prefix)
+
+	return
 }
 
 // Alert writes an ALERT-level message to this FileLogger.