skip imports for NNpops and openmmtorch if not triggered

Author: orionarcher

pyproject.toml

@@ -65,7 +65,7 @@ ase = ["ase>=3.23.0"]
 # tblite py3.12 support tracked in https://github.com/tblite/tblite/issues/198
 ase-ext = ["tblite>=0.3.0; python_version < '3.12'"]
 openmm = [
-    "mdanalysis>=2.7.0",
+    "mdanalysis>=2.8.0",
     "openmm-mdanalysis-reporter>=0.1.0",
     "openmm>=8.1.0",
 ]

src/atomate2/openmm/mace_utils.py

@@ -36,17 +36,30 @@ class written by Harry Moore. The nnpops_nl function
 import numpy as np
 import openmm
 import openmm.app
-import openmmtorch
 import torch
 from e3nn.util import jit
 from mace.tools import atomic_numbers_to_indices, to_one_hot, utils
 
 try:
     from NNPOps.neighbors import getNeighborPairs
-except ImportError as err:
-    raise ImportError(
-        "NNPOps is not installed. Please install it from conda-forge."
-    ) from err
+except ImportError:
+
+    def getNeighborPairs(*args, **kwargs) -> None:  # noqa: N802, ARG001
+        """Raise ImportError if NNPOps is not installed."""
+        raise ImportError(
+            "NNPOps is not installed. Please install it from conda-forge."
+        )
+
+
+try:
+    from openmmtorch import TorchForce
+except ImportError:
+
+    def TorchForce(*args, **kwargs) -> None:  # noqa: N802, ARG001
+        """Raise ImportError if openmmtorch is not installed."""
+        raise ImportError(
+            "openmmtorch is not installed. Please install it from conda-forge."
+        )
 
 
 class MaceForce(torch.nn.Module):
@@ -314,7 +327,7 @@ def add_forces(
         module = torch.jit.script(maceforce)
 
         # Create the TorchForce and add it to the System.
-        force = openmmtorch.TorchForce(module)
+        force = TorchForce(module)
         force.setForceGroup(0)
         force.setUsesPeriodicBoundaryConditions(periodic)
         system.addForce(force)