fix: preserve snapshot symlinks and guard incomplete upgrade copies

internal/api/snapshot_restore_test.go

@@ -11,6 +11,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"syscall"
 	"testing"
 )
 
@@ -122,6 +123,12 @@ func TestSnapshotFullRestore(t *testing.T) {
 	for _, running := range []bool{false, true} {
 		t.Run(fmt.Sprint(running), func(t *testing.T) {
 			a, i, home, id := snapshotRestoreFixture(t, running, "")
+			links := map[string]string{"absolute": "/workspace/example", "dangling": "missing", "loop": "loop", "relative": "data"}
+			for name, target := range links {
+				if err := os.Symlink(target, filepath.Join(filepath.Dir(home), id, name)); err != nil {
+					t.Fatal(err)
+				}
+			}
 			if err := a.recordSnapshot(i, id, i.Version, i.ImageID); err != nil {
 				t.Fatal(err)
 			}
@@ -140,6 +147,12 @@ func TestSnapshotFullRestore(t *testing.T) {
 				}
 			}
 			current, _ := a.s.GetInstance(i.ID)
+			for name, target := range links {
+				got, err := os.Readlink(filepath.Join(home, name))
+				if err != nil || got != target {
+					t.Fatalf("restored link %s: %q %v", name, got, err)
+				}
+			}
 			want := "exited"
 			if running {
 				want = "running"
@@ -169,6 +182,40 @@ func TestSnapshotRestoreRollback(t *testing.T) {
 	}
 }
 
+func TestIncompleteSnapshotNotRestorable(t *testing.T) {
+	a, i, _, id := snapshotRestoreFixture(t, false, "")
+	if _, err := a.s.DB.Exec("CREATE TABLE snapshot_copy_state (instance_id TEXT, id TEXT, ready INTEGER)"); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := a.s.DB.Exec("INSERT INTO snapshot_copy_state VALUES(?,?,0)", i.ID, id); err != nil {
+		t.Fatal(err)
+	}
+	w := configCall(a, i, "GET", "snapshots", "")
+	var list []snapshotInfo
+	if w.Code != 200 || json.Unmarshal(w.Body.Bytes(), &list) != nil || len(list) != 1 || list[0].Restorable || list[0].RestoreReason != "snapshot copy incomplete" {
+		t.Fatal(w.Code, w.Body.String())
+	}
+	w = configCall(a, i, "POST", "snapshots", snapshotRestoreBody(id, true))
+	if w.Code != 409 || !strings.Contains(w.Body.String(), "snapshot copy incomplete") {
+		t.Fatal(w.Code, w.Body.String())
+	}
+	if err := a.recordSnapshot(i, id, i.Version, i.ImageID); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := a.s.DB.Exec("UPDATE snapshot_copy_state SET ready=1"); err != nil {
+		t.Fatal(err)
+	}
+	if _, _, reason := a.snapshotCompatibility(i, id); reason != "" {
+		t.Fatal(reason)
+	}
+	if _, err := a.s.DB.Exec("ALTER TABLE snapshot_copy_state RENAME COLUMN ready TO unavailable"); err != nil {
+		t.Fatal(err)
+	}
+	if _, _, reason := a.snapshotCompatibility(i, id); reason != "snapshot completion metadata unavailable" {
+		t.Fatal(reason)
+	}
+}
+
 func TestSnapshotRestoreGuards(t *testing.T) {
 	for _, test := range []string{"unknown", "mismatch", "password", "confirm", "reader", "quota", "error", "unsafe", "foreign", "oversized"} {
 		t.Run(test, func(t *testing.T) {
@@ -196,7 +243,7 @@ func TestSnapshotRestoreGuards(t *testing.T) {
 			case "error":
 				a.s.SetInstance(i.ID, "error")
 			case "unsafe":
-				if err := os.Symlink("/etc/passwd", filepath.Join(filepath.Dir(home), id, "unsafe")); err != nil {
+				if err := syscall.Mkfifo(filepath.Join(filepath.Dir(home), id, "unsafe"), 0600); err != nil {
 					t.Fatal(err)
 				}
 				want = 400