helper: use generic extra files interface

This replaces the pipes object and integrates context into helper process lifecycle.

Signed-off-by: Ophestra <cat@gensokyo.uk>

helper/helper_test.go

@@ -1,6 +1,9 @@
 package helper_test
 
 import (
+	"context"
+	"errors"
+	"fmt"
 	"strconv"
 	"strings"
 	"testing"
@@ -23,20 +26,23 @@ var (
 	argsWt      = helper.MustNewCheckedArgs(wantArgs)
 )
 
-func argF(argsFD, statFD int) []string {
-	if argsFD == -1 {
+func argF(argsFd, statFd int) []string {
+	if argsFd == -1 {
 		panic("invalid args fd")
 	}
 
-	return argFChecked(argsFD, statFD)
+	return argFChecked(argsFd, statFd)
 }
 
-func argFChecked(argsFD, statFD int) []string {
-	if statFD == -1 {
-		return []string{"--args", strconv.Itoa(argsFD)}
-	} else {
-		return []string{"--args", strconv.Itoa(argsFD), "--fd", strconv.Itoa(statFD)}
+func argFChecked(argsFd, statFd int) (args []string) {
+	args = make([]string, 0, 4)
+	if argsFd > -1 {
+		args = append(args, "--args", strconv.Itoa(argsFd))
 	}
+	if statFd > -1 {
+		args = append(args, "--fd", strconv.Itoa(statFd))
+	}
+	return
 }
 
 // this function tests an implementation of the helper.Helper interface
@@ -45,66 +51,42 @@ func testHelper(t *testing.T, createHelper func() helper.Helper) {
 
 	t.Run("start helper with status channel and wait", func(t *testing.T) {
 		h := createHelper()
-		ready := make(chan error, 1)
-		cmd := h.Unwrap()
 
 		stdout, stderr := new(strings.Builder), new(strings.Builder)
-		cmd.Stdout, cmd.Stderr = stdout, stderr
+		h.Stdout(stdout).Stderr(stderr)
 
 		t.Run("wait not yet started helper", func(t *testing.T) {
-			wantErr := "exec: not started"
-			if err := h.Wait(); err != nil && err.Error() != wantErr {
-				t.Errorf("Wait(%v) error = %v, wantErr %v",
-					ready,
-					err, wantErr)
-				return
-			}
+			defer func() {
+				r := recover()
+				if r == nil {
+					t.Fatalf("Wait did not panic")
+				}
+			}()
+			panic(fmt.Sprintf("unreachable: %v", h.Wait()))
 		})
 
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+
 		t.Log("starting helper stub")
-		if err := h.StartNotify(ready); err != nil {
-			t.Errorf("StartNotify(%v) error = %v",
-				ready,
-				err)
+		if err := h.Start(ctx, true); err != nil {
+			t.Errorf("Start: error = %v", err)
+			cancel()
 			return
 		}
+		t.Log("cancelling context")
+		cancel()
 
 		t.Run("start already started helper", func(t *testing.T) {
 			wantErr := "exec: already started"
-			if err := h.StartNotify(ready); err != nil && err.Error() != wantErr {
-				t.Errorf("StartNotify(%v) error = %v, wantErr %v",
-					ready,
+			if err := h.Start(ctx, true); err != nil && err.Error() != wantErr {
+				t.Errorf("Start: error = %v, wantErr %v",
 					err, wantErr)
 				return
 			}
 		})
 
-		t.Log("waiting on status channel with timeout")
-		select {
-		case <-time.NewTimer(5 * time.Second).C:
-			t.Errorf("never got a ready response")
-			t.Errorf("stdout:\n%s", stdout.String())
-			t.Errorf("stderr:\n%s", stderr.String())
-			if err := cmd.Process.Kill(); err != nil {
-				panic(err.Error())
-			}
-			return
-		case err := <-ready:
-			if err != nil {
-				t.Errorf("StartNotify(%v) latent error = %v",
-					ready,
-					err)
-			}
-		}
-
-		t.Log("closing status pipe")
-		if err := h.Close(); err != nil {
-			t.Errorf("Close() error = %v",
-				err)
-		}
-
 		t.Log("waiting on helper")
-		if err := h.Wait(); err != nil {
+		if err := h.Wait(); !errors.Is(err, context.Canceled) {
 			t.Errorf("Wait() err = %v stderr = %s",
 				err, stderr)
 		}
@@ -112,51 +94,35 @@ func testHelper(t *testing.T, createHelper func() helper.Helper) {
 		t.Run("wait already finalised helper", func(t *testing.T) {
 			wantErr := "exec: Wait was already called"
 			if err := h.Wait(); err != nil && err.Error() != wantErr {
-				t.Errorf("Wait(%v) error = %v, wantErr %v",
-					ready,
+				t.Errorf("Wait: error = %v, wantErr %v",
 					err, wantErr)
 				return
 			}
 		})
 
 		if got := stdout.String(); !strings.HasPrefix(got, wantPayload) {
-			t.Errorf("StartNotify(%v) stdout = %v, want %v",
-				ready,
+			t.Errorf("Start: stdout = %v, want %v",
 				got, wantPayload)
 		}
 	})
 
 	t.Run("start helper and wait", func(t *testing.T) {
 		h := createHelper()
-		cmd := h.Unwrap()
 
 		stdout, stderr := new(strings.Builder), new(strings.Builder)
-		cmd.Stdout, cmd.Stderr = stdout, stderr
+		h.Stdout(stdout).Stderr(stderr)
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
 
-		if err := h.Start(); err != nil {
+		if err := h.Start(ctx, false); err != nil {
 			t.Errorf("Start() error = %v",
 				err)
 			return
 		}
 
-		t.Run("close helper without status pipe", func(t *testing.T) {
-			defer func() {
-				wantPanic := "attempted to close helper with no status pipe"
-				if r := recover(); r != wantPanic {
-					t.Errorf("Close() panic = %v, wantPanic %v",
-						r, wantPanic)
-				}
-			}()
-			if err := h.Close(); err != nil {
-				t.Errorf("Close() error = %v",
-					err)
-				return
-			}
-		})
-
 		if err := h.Wait(); err != nil {
-			t.Errorf("Wait() err = %v stderr = %s",
-				err, stderr)
+			t.Errorf("Wait() err = %v stdout = %s stderr = %s",
+				err, stdout, stderr)
 		}
 
 		if got := stdout.String(); !strings.HasPrefix(got, wantPayload) {