fix(pm): retain chained library aliases on no-symlink hosts

Resolve deferred relative file links until no further alias can be materialized. Keep containment checks and leave unresolved cross-package copyright links alone.

pm/package.py

@@ -288,14 +288,23 @@ class DebPackage(Package):
                     target.chmod(member.mode & 0o777)
                 except OSError:
                     pass
-        for _linkname, target, resolved_path in deferred_links:
-            if not _contained(resolved_path):
-                raise InstallError(
-                    self.name,
-                    f"symlink {target.name} resolves outside the staged tree",
-                )
-            if not (target.exists() or target.is_symlink()) and resolved_path.is_file():
-                shutil.copy2(resolved_path, target)
+        while deferred_links:
+            pending = []
+            for linkname, target, resolved_path in deferred_links:
+                if not _contained(resolved_path):
+                    raise InstallError(
+                        self.name,
+                        f"symlink {target.name} resolves outside the staged tree",
+                    )
+                if target.exists() or target.is_symlink():
+                    continue
+                if resolved_path.is_file():
+                    shutil.copy2(resolved_path, target)
+                else:
+                    pending.append((linkname, target, resolved_path))
+            if len(pending) == len(deferred_links):
+                break
+            deferred_links = pending
         # Termux debs carry owner-only modes across the whole tree (700 on
         # binaries n libs, 600 on stdlib .py files) -- postinst would
         # normalize on a real phone, but pm extracts without postinst, and

tests/pm/test_deb_safety.py

@@ -65,6 +65,25 @@ def _symlink_member(name: str, linkname: str) -> tarfile.TarInfo:
     return info
 
 
+def test_chained_aliases_survive_without_symlink_support(tmp_path, monkeypatch):
+    def unavailable(*args, **kwargs):
+        raise OSError("symlinks unavailable")
+
+    monkeypatch.setattr(Path, "symlink_to", unavailable)
+    deb = tmp_path / "aliases.deb"
+    lib = "data/data/com.termux/files/usr/lib"
+    _build_deb(deb, [
+        _symlink_member(f"{lib}/libexample.so", "libexample.so.1"),
+        _symlink_member(f"{lib}/libexample.so.1", "libexample.so.1.2"),
+        (f"{lib}/libexample.so.1.2", b"library payload"),
+    ])
+    staged = tmp_path / "staged"
+    staged.mkdir()
+    _P().unpack(deb, staged, "linux-arm64-bionic")
+    for name in ("libexample.so", "libexample.so.1", "libexample.so.1.2"):
+        assert (staged / lib / name).read_bytes() == b"library payload"
+
+
 def test_absolute_symlink_target_rejected(tmp_path: Path):
     """A member whose symlink target is ABSOLUTE must be refused outright:
     the link points outside the staged tree the moment it is created."""