Transfer completed Go output without copies

internal/gotool/gotool_test.go

@@ -1,6 +1,7 @@
 package gotool
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
@@ -62,6 +63,14 @@ func runGoPreparationFixture() int {
 	case "fail":
 		fmt.Fprintln(os.Stderr, "fixture dependency failure")
 		return 23
+	case "output":
+		fmt.Fprintln(os.Stdout, "fixture stdout")
+		fmt.Fprintln(os.Stderr, "fixture stderr")
+		return 0
+	case "large-fail":
+		_, _ = fmt.Fprint(os.Stdout, strings.Repeat("x", 8<<20))
+		fmt.Fprintln(os.Stderr, "fixture large failure")
+		return 23
 	case "wait":
 		for {
 			time.Sleep(time.Second)
@@ -295,7 +304,7 @@ func TestPersistentSettingsPreserveCachesAndNativeCTools(t *testing.T) {
 func readSettings(t *testing.T, tool *Tool, mode Mode, target Target, names ...string) map[string]string {
 	t.Helper()
 	args := append([]string{"env", "-json"}, names...)
-	output, err := tool.Run(context.Background(), t.TempDir(), mode, target, nil, args...)
+	output, err := tool.Output(context.Background(), t.TempDir(), mode, target, nil, args...)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -306,6 +315,122 @@ func readSettings(t *testing.T, tool *Tool, mode Mode, target Target, names ...s
 	return settings
 }
 
+func TestOutputReturnsAndForwardsCombinedOutput(t *testing.T) {
+	repository, _ := installGoPreparationFixture(t)
+	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "output")
+	tool := fixtureTool()
+	var forwarded bytes.Buffer
+
+	output, err := tool.Output(context.Background(), repository, Native, Target{}, &forwarded, "version")
+	if err != nil {
+		t.Fatalf("Output() error = %v", err)
+	}
+	if !bytes.Contains(output, []byte("fixture stdout")) || !bytes.Contains(output, []byte("fixture stderr")) {
+		t.Fatalf("combined output = %q", output)
+	}
+	if !bytes.Equal(forwarded.Bytes(), output) {
+		t.Fatalf("forwarded output differs from capture: forwarded %d bytes, captured %d", forwarded.Len(), len(output))
+	}
+}
+
+func TestRunForwardsOutputWithoutReturningCapture(t *testing.T) {
+	repository, _ := installGoPreparationFixture(t)
+	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "output")
+	tool := fixtureTool()
+	var forwarded bytes.Buffer
+
+	if err := tool.Run(context.Background(), repository, Native, Target{}, &forwarded, "version"); err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if !bytes.Contains(forwarded.Bytes(), []byte("fixture stdout")) || !bytes.Contains(forwarded.Bytes(), []byte("fixture stderr")) {
+		t.Fatalf("forwarded output = %q", forwarded.String())
+	}
+}
+
+func TestRunPreservesFailureDiagnosticsAndCause(t *testing.T) {
+	repository, _ := installGoPreparationFixture(t)
+	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "fail")
+	tool := fixtureTool()
+
+	err := tool.Run(context.Background(), repository, Native, Target{}, nil, "version")
+	var exitError *exec.ExitError
+	if !errors.As(err, &exitError) || exitError.ExitCode() != 23 || !strings.Contains(err.Error(), "fixture dependency failure") {
+		t.Fatalf("Run() error = %v", err)
+	}
+}
+
+func TestOutputReturnsLargeFailureDiagnosticsAndCause(t *testing.T) {
+	repository, _ := installGoPreparationFixture(t)
+	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "large-fail")
+	tool := fixtureTool()
+
+	output, err := tool.Output(context.Background(), repository, Native, Target{}, nil, "version")
+	var exitError *exec.ExitError
+	wantSize := (8 << 20) + len("fixture large failure\n")
+	if len(output) != wantSize {
+		t.Fatalf("captured output = %d bytes, want %d", len(output), wantSize)
+	}
+	if !errors.As(err, &exitError) || exitError.ExitCode() != 23 || !strings.Contains(err.Error(), "fixture large failure") {
+		t.Fatalf("Output() error = %v", err)
+	}
+}
+
+func TestOutputReturnsCancellation(t *testing.T) {
+	repository, recordPath := installGoPreparationFixture(t)
+	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "wait")
+	tool := fixtureTool()
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	done := make(chan error, 1)
+	go func() {
+		_, err := tool.Output(ctx, repository, Native, Target{}, nil, "version")
+		done <- err
+	}()
+
+	deadline := time.Now().Add(5 * time.Second)
+	for {
+		if _, err := os.Stat(recordPath); err == nil {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Fatal("Go fixture did not start")
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	cancel()
+	select {
+	case err := <-done:
+		if !errors.Is(err, context.Canceled) {
+			t.Fatalf("Output() error = %v; want cancellation", err)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("Go fixture did not stop after cancellation")
+	}
+}
+
+func TestOutputPreservesForwardingWriterFailure(t *testing.T) {
+	repository, _ := installGoPreparationFixture(t)
+	t.Setenv("RELEASEKIT_GO_FIXTURE_MODE", "output")
+	tool := fixtureTool()
+	writerErr := errors.New("fixture output writer failed")
+
+	output, err := tool.Output(context.Background(), repository, Native, Target{}, failingOutputWriter{err: writerErr}, "version")
+	if !errors.Is(err, writerErr) || !strings.Contains(err.Error(), "go version") {
+		t.Fatalf("Output() error = %v; want wrapped writer error and command", err)
+	}
+	if len(output) == 0 {
+		t.Fatal("Output() returned no captured bytes after forwarding failed")
+	}
+}
+
+type failingOutputWriter struct{ err error }
+
+func (writer failingOutputWriter) Write([]byte) (int, error) { return 0, writer.err }
+
+func fixtureTool() *Tool {
+	return &Tool{host: Target{OS: runtime.GOOS, Arch: runtime.GOARCH}, settings: map[string]string{}}
+}
+
 func clearGoSettings(t *testing.T) {
 	t.Helper()
 	for _, key := range []string{