Add piped child process support

internal/process/process_test.go

@@ -1,10 +1,12 @@
 package process
 
 import (
+	"bufio"
 	"bytes"
 	"context"
 	"errors"
 	"fmt"
+	"io"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -117,6 +119,146 @@ func TestRunReturnsCancellation(t *testing.T) {
 	}
 }
 
+func TestStartPipedExchangesBeforeInputEOFAndPreservesSettings(t *testing.T) {
+	workdir := filepath.Join(t.TempDir(), "piped directory")
+	if err := os.Mkdir(workdir, 0o700); err != nil {
+		t.Fatal(err)
+	}
+	t.Setenv("RELEASEKIT_PROCESS_OVERLAY", "parent")
+	t.Setenv("RELEASEKIT_PROCESS_INHERITED", "inherited")
+	var stderr bytes.Buffer
+	child, err := StartPiped(context.Background(), Invocation{
+		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "argument with spaces", "exchange"},
+		Dir:  workdir,
+		Env: map[string]string{
+			"RELEASEKIT_PROCESS_HELPER":  "1",
+			"RELEASEKIT_PROCESS_OVERLAY": "child",
+		},
+		Stderr: &stderr,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := io.WriteString(child.Stdin(), "request\n"); err != nil {
+		t.Fatal(err)
+	}
+	response, err := bufio.NewReader(child.Stdout()).ReadString('\n')
+	if err != nil {
+		t.Fatalf("read response before closing input: %v", err)
+	}
+	want := fmt.Sprintf("request|%s|argument with spaces|child|inherited\n", workdir)
+	if response != want {
+		t.Fatalf("piped response = %q, want %q", response, want)
+	}
+	if err := child.Stdin().Close(); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := io.Copy(io.Discard, child.Stdout()); err != nil {
+		t.Fatal(err)
+	}
+	if err := child.Wait(); err != nil {
+		t.Fatal(err)
+	}
+	if got := stderr.String(); got != "child stderr\n" {
+		t.Fatalf("child stderr = %q, want %q", got, "child stderr\n")
+	}
+	if got := os.Getenv("RELEASEKIT_PROCESS_OVERLAY"); got != "parent" {
+		t.Fatalf("parent environment changed: got %q, want %q", got, "parent")
+	}
+}
+
+func TestStartPipedCancellationAfterReadinessReapsChild(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	child, err := StartPiped(ctx, Invocation{
+		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "unused", "wait"},
+		Env:  map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
+	})
+	if err != nil {
+		cancel()
+		t.Fatal(err)
+	}
+	line, err := bufio.NewReader(child.Stdout()).ReadString('\n')
+	if err != nil || line != "started\n" {
+		cancel()
+		_ = child.Stdin().Close()
+		_ = child.Stdout().Close()
+		_ = child.Wait()
+		t.Fatalf("readiness = %q, %v; want started signal", line, err)
+	}
+	cancel()
+	if err := child.Stdin().Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := child.Stdout().Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := child.Wait(); !errors.Is(err, context.Canceled) {
+		t.Fatalf("Wait() error = %v, want context cancellation", err)
+	}
+}
+
+func TestStartPipedCancelDoesNotCancelParentContext(t *testing.T) {
+	ctx := context.Background()
+	child, err := StartPiped(ctx, Invocation{
+		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "unused", "wait"},
+		Env:  map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	line, err := bufio.NewReader(child.Stdout()).ReadString('\n')
+	if err != nil || line != "started\n" {
+		child.Cancel()
+		_ = child.Stdin().Close()
+		_ = child.Stdout().Close()
+		_ = child.Wait()
+		t.Fatalf("readiness = %q, %v; want started signal", line, err)
+	}
+	child.Cancel()
+	if err := child.Stdin().Close(); err != nil {
+		t.Fatal(err)
+	}
+	if err := child.Stdout().Close(); err != nil {
+		t.Fatal(err)
+	}
+	err = child.Wait()
+	var exitErr *exec.ExitError
+	if !errors.As(err, &exitErr) {
+		t.Fatalf("Wait() error = %v, want interrupted child exit", err)
+	}
+	if ctx.Err() != nil {
+		t.Fatalf("child cancellation changed parent context: %v", ctx.Err())
+	}
+}
+
+func TestStartPipedReportsStartFailure(t *testing.T) {
+	child, err := StartPiped(context.Background(), Invocation{Args: []string{"releasekit-command-that-does-not-exist"}})
+	if err == nil || child != nil || !strings.Contains(err.Error(), "releasekit-command-that-does-not-exist") {
+		t.Fatalf("StartPiped() = %#v, %v; want a missing executable error", child, err)
+	}
+}
+
+func TestStartPipedPreservesNonzeroExit(t *testing.T) {
+	child, err := StartPiped(context.Background(), Invocation{
+		Args: []string{helperExecutable(t), "-test.run=TestProcessHelper", "--", "unused", "exit"},
+		Env:  map[string]string{"RELEASEKIT_PROCESS_HELPER": "1"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := child.Stdin().Close(); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := io.Copy(io.Discard, child.Stdout()); err != nil {
+		t.Fatal(err)
+	}
+	err = child.Wait()
+	var exitErr *exec.ExitError
+	if !errors.As(err, &exitErr) || exitErr.ExitCode() != 7 {
+		t.Fatalf("Wait() error = %v, want exit code 7", err)
+	}
+}
+
 func TestProcessHelper(t *testing.T) {
 	if os.Getenv("RELEASEKIT_PROCESS_HELPER") != "1" {
 		return
@@ -142,6 +284,21 @@ func TestProcessHelper(t *testing.T) {
 		for {
 			time.Sleep(time.Second)
 		}
+	case "exchange":
+		reader := bufio.NewReader(os.Stdin)
+		request, err := reader.ReadString('\n')
+		if err != nil {
+			os.Exit(11)
+		}
+		workdir, err := os.Getwd()
+		if err != nil {
+			os.Exit(12)
+		}
+		fmt.Fprintf(os.Stdout, "%s|%s|%s|%s|%s\n", strings.TrimSuffix(request, "\n"), workdir, args[len(args)-2], os.Getenv("RELEASEKIT_PROCESS_OVERLAY"), os.Getenv("RELEASEKIT_PROCESS_INHERITED"))
+		fmt.Fprintln(os.Stderr, "child stderr")
+		if _, err := io.Copy(io.Discard, reader); err != nil {
+			os.Exit(13)
+		}
 	default:
 		os.Exit(10)
 	}