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

@@ -123,6 +123,9 @@ def get_protocol_filepath(cls):
     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.
         :param protocol: protocol to use, if not specified, the default will be used.

src/aiida_quantumespresso/workflows/pw/base.py

@@ -1,5 +1,7 @@
 # -*- coding: utf-8 -*-
 """Workchain to run a Quantum ESPRESSO pw.x calculation with automated error handling and restarts."""
+import warnings
+
 from aiida import orm
 from aiida.common import AttributeDict, exceptions
 from aiida.common.lang import type_check
@@ -117,6 +119,9 @@ 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.
         :param protocol: protocol to use, if not specified, the default will be used.
@@ -208,6 +213,12 @@ 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)
 

src/aiida_quantumespresso/workflows/pw/relax.py

@@ -90,6 +90,9 @@ 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.
         :param protocol: protocol to use, if not specified, the default will be used.