Modify behaviour to request all rules in a group to be set as preempt…

…ible instances

docs/snakefiles/rules.rst

@@ -1341,7 +1341,7 @@ However, if we would add ``group: "mygroup"`` to rule ``c``, all jobs would end
 Alternatively, groups can be defined via the command line interface.
 This enables to almost arbitrarily partition the DAG, e.g. in order to safe network traffic, see :ref:`here <job_grouping>`.
 
-For execution on the cloud using Google Life Science API and preemptible instances, note than if any of the rules in a group is included in the subset of rules to be executed using preembtible instances (with command line option ``--preemptible-rules``), the group will be also scheduled to be executed on a preemptible instance.
+For execution on the cloud using Google Life Science API and preemptible instances, we expect all rules in the group to be homogenously set as preemptible instances (e.g., with command-line option ``--preemptible-rules``), such that a preemptible VM is requested for the execution of the group job.
 
 Piped output
 ------------

snakemake/executors/google_lifesciences.py

@@ -512,7 +512,13 @@ def _generate_job_resources(self, job):
         )
 
         if job.is_group():
-            preemptible = any(rule in self.preemptible_rules for rule in job.rules)
+            preemptible = all(rule in self.preemptible_rules for rule in job.rules)
+            if not preemtible and any(
+                rule in self.preemptible_rules for rule in job.rules
+            ):
+                raise WorkflowError(
+                    "All grouped rules should be homogenously set as preemptible rules"
+                )
         else:
             preemptible = job.rule.name in self.preemptible_rules
         # We add the size for the image itself (10 GB) to bootDiskSizeGb