New process chain style fails for importer/exporter module

[mmacata]

This is a rare case as usually the importer or exporter is used with GRASS GIS to create process chains and communicate with actinia and are not used within a process chain. Exception is the interface description which is requested by the actinia-module-plugin.

old style SUCCESS:

{'1': {'module': 'exporter', 'interface-description': True}}

new style ERROR:

{'version': 1, 'list': [{'id': '1', 'module': 'exporter', 'interface-description': True}]}

'exception': {'message': 'AsyncProcessError: Empty process chain, nothing to compute', 'traceback': [' File "/usr/lib/python3.8/site-packages/actinia_core-1.0.1+g3ea04d5.dirty-py3.8.egg/actinia_core/rest/ephemeral_processing.py", line 1732, in run\n self._execute()\n', ' File "/src/actinia-module-plugin/actinia_module_plugin/core/modules/processor.py", line 163, in _execute\n process_list = self._validate_process_chain(\n', ' File "/usr/lib/python3.8/site-packages/actinia_core-1.0.1+g3ea04d5.dirty-py3.8.egg/actinia_core/rest/ephemeral_processing.py", line 669, in _validate_process_chain\n raise AsyncProcessError("Empty process chain, nothing to compute")\n'], 'type': "<class 'actinia_core.core.common.exceptions.AsyncProcessError'>"}

As the old style still works, this is not urgent but documented here in case we no longer support it.

[mmacata]

Reason might be, that this error happens only for interface description because it might have not been adjusted for new style. Related code:

• https://github.com/mundialis/actinia_core/blob/2961373a5e284c2fc600506f50c1ace7833da79a/src/actinia_core/core/common/process_chain.py#L550
• https://github.com/mundialis/actinia_core/blob/3292c19bdce0033195a25f1acf6fc52aac22e29c/src/actinia_core/models/process_chain.py