First steps to make protocols scheduler agnostic.

The current protocols implicitly rely on the `Slurm` scheduler by specifying the number of machines
in `metadata.options.resources`. This can cause problems when using different schedulers
in combination with `get_builder_from_protocol`. Here, we add this information to the documentation
and add a warning that the options need to be explicitly specified in future versions.

src/aiida_quantumespresso/workflows/pw/bands.py

@@ -122,6 +122,8 @@ def get_protocol_filepath(cls):
     @classmethod
     def get_builder_from_protocol(cls, code, structure, protocol=None, overrides=None, options=None, **kwargs):
         """Return a builder prepopulated with inputs selected according to the chosen protocol.
+        The current protocols rely on the `Slurm` scheduler. To use them nonetheless with a different scheduler, the
+        protocols might need to be adjusted and explicit resources need to be provided in `options`.
 
         :param code: the ``Code`` instance configured for the ``quantumespresso.pw`` plugin.
         :param structure: the ``StructureData`` instance to use.

src/aiida_quantumespresso/workflows/pw/base.py

@@ -9,6 +9,7 @@
 from aiida_quantumespresso.calculations.functions.create_kpoints_from_distance import create_kpoints_from_distance
 from aiida_quantumespresso.common.types import ElectronicType, RestartType, SpinType
 from aiida_quantumespresso.utils.defaults.calculation import pw as qe_defaults
+import warnings
 
 from ..protocols.utils import ProtocolMixin
 
@@ -116,6 +117,8 @@ def get_builder_from_protocol(
         **_
     ):
         """Return a builder prepopulated with inputs selected according to the chosen protocol.
+        The current protocols rely on the `Slurm` scheduler. To use them nonetheless with a different scheduler, the
+        protocols might need to be adjusted and explicit resources need to be provided in `options`.
 
         :param code: the ``Code`` instance configured for the ``quantumespresso.pw`` plugin.
         :param structure: the ``StructureData`` instance to use.
@@ -208,9 +211,15 @@ def get_builder_from_protocol(
 
         metadata = inputs['pw']['metadata']
 
+        if not options or options.get('resources', None) is None:
+            warnings.warn(
+                'No explicit resources were provided for `metadata.options.resources`. This approach is '
+                'deprecated and will cause an error in future versions.', UserWarning
+            )
+
         if options:
             metadata['options'] = recursive_merge(inputs['pw']['metadata']['options'], options)
-
+        
         # pylint: disable=no-member
         builder = cls.get_builder()
         builder.pw['code'] = code

src/aiida_quantumespresso/workflows/pw/relax.py

@@ -89,6 +89,8 @@ def get_builder_from_protocol(
         **kwargs
     ):
         """Return a builder prepopulated with inputs selected according to the chosen protocol.
+        The current protocols rely on the `Slurm` scheduler. To use them nonetheless with a different scheduler, the
+        protocols might need to be adjusted and explicit resources need to be provided in `options`.
 
         :param code: the ``Code`` instance configured for the ``quantumespresso.pw`` plugin.
         :param structure: the ``StructureData`` instance to use.