From 3057f470d437f372b8590d790d8c6661f80f8c56 Mon Sep 17 00:00:00 2001
From: Brian Picciano <mediocregopher@gmail.com>
Date: Sat, 22 Jan 2022 20:36:07 -0700
Subject: [PATCH] Expose RunProcessOnce and PlainLogger

---
 pmuxproc/logger.go   | 19 +++++++++++++++++++
 pmuxproc/pmuxproc.go | 16 ++++++++++++++--
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/pmuxproc/logger.go b/pmuxproc/logger.go
index d5980f1..d330538 100644
--- a/pmuxproc/logger.go
+++ b/pmuxproc/logger.go
@@ -1,5 +1,10 @@
 package pmuxproc
 
+import (
+	"fmt"
+	"io"
+)
+
 // Logger is used by RunProcess to log process details in realtime. You can use
 // a new(NullLogger) if you don't care.
 type Logger interface {
@@ -12,3 +17,17 @@ type NullLogger struct{}
 
 func (*NullLogger) Println(string)                {}
 func (*NullLogger) Printf(string, ...interface{}) {}
+
+// PlainLogger implements Logger by writing each line directly to the given
+// io.Writer as-is.
+type PlainLogger struct {
+	io.Writer
+}
+
+func (l PlainLogger) Println(line string) {
+	fmt.Fprintln(l, line)
+}
+
+func (l PlainLogger) Printf(str string, args ...interface{}) {
+	fmt.Fprintf(l, str, args...)
+}
diff --git a/pmuxproc/pmuxproc.go b/pmuxproc/pmuxproc.go
index a807ced..ce1d23a 100644
--- a/pmuxproc/pmuxproc.go
+++ b/pmuxproc/pmuxproc.go
@@ -57,7 +57,18 @@ func (cfg Config) withDefaults() Config {
 	return cfg
 }
 
-func runProcessOnce(ctx context.Context, logger Logger, cfg Config) error {
+// RunProcessOnce runs the process described by the Config (though it doesn't
+// use all fields from the Config). The process is killed if the context is
+// canceled.
+//
+// It returns nil if the process exits normally with a zero status. It returns
+// an error otherwise.
+//
+// The stdout and stderr of the process will be written to the given Logger, as
+// well as various runtime events.
+func RunProcessOnce(ctx context.Context, logger Logger, cfg Config) error {
+
+	cfg = cfg.withDefaults()
 
 	var wg sync.WaitGroup
 
@@ -111,6 +122,7 @@ func runProcessOnce(ctx context.Context, logger Logger, cfg Config) error {
 	// in order to ensure this go-routine always gets cleaned up.
 	stopCh := make(chan struct{})
 	defer close(stopCh)
+
 	go func(proc *os.Process) {
 		select {
 		case <-ctx.Done():
@@ -154,7 +166,7 @@ func RunProcess(ctx context.Context, logger Logger, cfg Config) {
 
 	for {
 		start := time.Now()
-		err := runProcessOnce(ctx, logger, cfg)
+		err := RunProcessOnce(ctx, logger, cfg)
 		took := time.Since(start)
 
 		if err != nil {