Preserve validation cancellation during reader shutdown

internal/validation/tree.go

@@ -13,6 +13,7 @@ import (
 // CandidateTree is an inventory of one captured commit with blob contents
 // loaded lazily by object ID.
 type CandidateTree struct {
+	context        context.Context
 	repositoryDir  string
 	entries        []git.TreeEntry
 	byPath         map[string]int
@@ -24,13 +25,14 @@ type CandidateTree struct {
 }
 
 // ReadCandidateTree enumerates the captured commit without reading from the
-// worktree.
+// worktree. The supplied context also governs the scoped reader through closure.
 func ReadCandidateTree(ctx context.Context, repositoryDir, commit string) (*CandidateTree, error) {
 	entries, err := git.ReadTree(ctx, repositoryDir, commit)
 	if err != nil {
 		return nil, err
 	}
 	tree := &CandidateTree{
+		context:        ctx,
 		repositoryDir:  repositoryDir,
 		entries:        entries,
 		byPath:         make(map[string]int, len(entries)),
@@ -104,10 +106,12 @@ func (tree *CandidateTree) readBlob(ctx context.Context, entry git.TreeEntry) ([
 		return nil, fmt.Errorf("read committed path %q: candidate tree is closed", entry.Path)
 	}
 	if tree.blobReader == nil {
-		// The reader belongs to the tree and can outlive an individual read
-		// context. Each Read call still applies its own cancellation to the
-		// in-flight exchange.
-		tree.blobReader = git.NewBlobReader(context.Background(), tree.repositoryDir)
+		// The operation context governs shutdown independently of each read.
+		operationContext := tree.context
+		if operationContext == nil {
+			operationContext = context.Background()
+		}
+		tree.blobReader = git.NewBlobReader(operationContext, tree.repositoryDir)
 	}
 	contents, err := tree.blobReader.Read(ctx, entry.ObjectID)
 	if err != nil {

internal/validation/tree_lifecycle_test.go

@@ -7,7 +7,9 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strconv"
 	"strings"
+	"syscall"
 	"testing"
 	"time"
 )
@@ -93,6 +95,55 @@ exec sleep 60`)
 	}
 }
 
+func TestRunPreservesCancellationDuringReaderShutdown(t *testing.T) {
+	repository := newTreeRepository(t)
+	writeTreeFile(t, repository, "go.mod", []byte("module fixture.example/app\n\ngo 1.25.0\n"))
+	writeTreeFile(t, repository, "main.go", []byte("package app\n\nconst value = 1\n"))
+	commit := commitCandidateTree(t, repository)
+	ready := filepath.Join(t.TempDir(), "shutdown-ready")
+	installLifecycleTools(t, `while IFS= read -r object; do
+  size=$("$RELEASEKIT_REAL_GIT" -C "$PWD" cat-file -s "$object")
+  printf '%s blob %s\n' "$object" "$size"
+  "$RELEASEKIT_REAL_GIT" -C "$PWD" cat-file blob "$object"
+  printf '\n'
+done
+printf '%s\n' "$$" > "$RELEASEKIT_GIT_READER_READY"
+exec sleep 60`)
+	t.Setenv("RELEASEKIT_GIT_READER_READY", ready)
+	ctx, cancel := context.WithCancel(t.Context())
+	defer cancel()
+	result := make(chan error, 1)
+	go func() { result <- Run(ctx, lifecycleRequest(repository, commit)) }()
+	waitForLifecycleFile(t, ready)
+	pidBytes, err := os.ReadFile(ready)
+	if err != nil {
+		t.Fatal(err)
+	}
+	pid, err := strconv.Atoi(strings.TrimSpace(string(pidBytes)))
+	if err != nil {
+		t.Fatal(err)
+	}
+	child, err := os.FindProcess(pid)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cancel()
+	select {
+	case err := <-result:
+		var failure *Failure
+		if !errors.As(err, &failure) || failure.Check != GoFormat || !errors.Is(err, context.Canceled) {
+			t.Fatalf("Run() error = %v, want GoFormat cancellation cause", err)
+		}
+		if err := child.Signal(syscall.Signal(0)); !errors.Is(err, syscall.ESRCH) && !errors.Is(err, os.ErrProcessDone) {
+			t.Fatalf("child signal after Run() = %v, want reaped child", err)
+		}
+	case <-time.After(5 * time.Second):
+		_ = child.Kill()
+		<-result
+		t.Fatal("Run() did not return after cancellation during reader shutdown")
+	}
+}
+
 func lifecycleRequest(repository, commit string) Request {
 	return Request{
 		RepositoryDir: repository,