fix(pt_expt): let deepmd.pt import errors propagate in comm op check

deepmd/pt_expt/utils/comm.py

@@ -50,25 +50,38 @@ def _check_underlying_ops_loaded() -> None:
     like DDP-spawned subprocesses that re-import modules from scratch
     and never see the test conftest's ``import deepmd.pt``.
     """
-    if not (
-        hasattr(torch.ops, "deepmd_export")
-        and hasattr(torch.ops.deepmd_export, "border_op")
-        and hasattr(torch.ops.deepmd_export, "border_op_backward")
-    ):
+
+    def _ops_registered() -> bool:
+        return (
+            hasattr(torch.ops, "deepmd_export")
+            and hasattr(torch.ops.deepmd_export, "border_op")
+            and hasattr(torch.ops.deepmd_export, "border_op_backward")
+        )
+
+    import_err: Exception | None = None
+    if not _ops_registered():
         # Triggers cxx_op.py which torch.ops.load_library's the .so.
         try:
             import deepmd.pt  # noqa: F401
-        except Exception:
-            # If deepmd.pt itself fails to import, fall through to the
-            # explicit RuntimeError below — clearer than re-raising a
-            # potentially-unrelated import error.
-            pass
-
-    if not (
-        hasattr(torch.ops, "deepmd_export")
-        and hasattr(torch.ops.deepmd_export, "border_op")
-        and hasattr(torch.ops.deepmd_export, "border_op_backward")
-    ):
+        except Exception as exc:
+            # ``deepmd/pt/__init__.py`` loads ``cxx_op`` (which registers
+            # the ops) before running ``load_entry_point("deepmd.pt")``.
+            # A broken third-party entry point can make the import raise
+            # *after* the ops were already registered, so only re-raise
+            # when the registration is still missing — that branch is the
+            # one where the error (typically an ``undefined symbol`` ABI
+            # mismatch against libdeepmd_op_pt.so) carries the diagnostic
+            # detail that the generic RuntimeError below would hide.
+            import_err = exc
+
+    if not _ops_registered():
+        if import_err is not None:
+            # Surface the raw import error (typically ``ImportError`` with
+            # ``undefined symbol`` ABI detail) instead of burying it in a
+            # generic message — that detail is what tells the user the
+            # mismatch is between libdeepmd_op_pt.so and the runtime torch,
+            # not a missing build.
+            raise import_err
         raise RuntimeError(
             "torch.ops.deepmd_export.{border_op,border_op_backward} "
             "are not registered. Build libdeepmd_op_pt.so and ensure "