Add support for recursive list, dict, and tuple ref parsing for pipeline controller.add step() parameter override (#1099)

* feat: ✨ Added optional support for list, dicts, tuples in Pipeline parameter_overrides

* style: 🎨 Updated to pass the flake8 formatting guidelines

* docs: 📝 There was a small typo I noticed in the documentation. Two extra '

clearml/automation/controller.py

@@ -81,6 +81,7 @@ class PipelineController(object):
         parents = attrib(type=list, default=None)  # list of parent DAG steps
         timeout = attrib(type=float, default=None)  # execution timeout limit
         parameters = attrib(type=dict, default=None)  # Task hyper-parameters to change
+        recursively_parse_parameters = attrib(type=bool, default=False)  # if True, recursively parse parameters in lists, dicts, or tuples
         configurations = attrib(type=dict, default=None)  # Task configuration objects to change
         task_overrides = attrib(type=dict, default=None)  # Task overrides to change
         executed = attrib(type=str, default=None)  # The actual executed Task ID (None if not executed yet)
@@ -368,6 +369,7 @@ class PipelineController(object):
             base_task_id=None,  # type: Optional[str]
             parents=None,  # type: Optional[Sequence[str]]
             parameter_override=None,  # type: Optional[Mapping[str, Any]]
+            recursively_parse_parameters=False,  # type: bool
             configuration_overrides=None,  # type: Optional[Mapping[str, Union[str, Mapping]]]
             task_overrides=None,  # type: Optional[Mapping[str, Any]]
             execution_queue=None,  # type: Optional[str]
@@ -405,7 +407,10 @@ class PipelineController(object):
           - Parameter access ``parameter_override={'Args/input_file': '${<step_name>.parameters.Args/input_file}' }``
           - Pipeline Task argument (see `Pipeline.add_parameter`) ``parameter_override={'Args/input_file': '${pipeline.<pipeline_parameter>}' }``
           - Task ID ``parameter_override={'Args/input_file': '${stage3.id}' }``
-
+        :param recursively_parse_parameters: If True, recursively parse parameters from parameter_override in lists, dicts, or tuples.
+            Example:
+            - ``parameter_override={'Args/input_file': ['${<step_name>.artifacts.<artifact_name>.url}', 'file2.txt']}`` will be correctly parsed.
+            - ``parameter_override={'Args/input_file': ('${<step_name_1>.parameters.Args/input_file}', '${<step_name_2>.parameters.Args/input_file}')}`` will be correctly parsed.
         :param configuration_overrides: Optional, override Task configuration objects.
             Expected dictionary of configuration object name and configuration object content.
             Examples:
@@ -572,6 +577,7 @@ class PipelineController(object):
             name=name, base_task_id=base_task_id, parents=parents or [],
             queue=execution_queue, timeout=time_limit,
             parameters=parameter_override or {},
+            recursively_parse_parameters=recursively_parse_parameters,
             configurations=configuration_overrides,
             clone_task=clone_base_task,
             task_overrides=task_overrides,
@@ -2237,7 +2243,7 @@ class PipelineController(object):
 
         updated_hyper_parameters = {}
         for k, v in node.parameters.items():
-            updated_hyper_parameters[k] = self._parse_step_ref(v)
+            updated_hyper_parameters[k] = self._parse_step_ref(v, recursive=node.recursively_parse_parameters)
 
         task_overrides = self._parse_task_overrides(node.task_overrides) if node.task_overrides else None
 
@@ -2776,11 +2782,12 @@ class PipelineController(object):
             except Exception:
                 pass
 
-    def _parse_step_ref(self, value):
+    def _parse_step_ref(self, value, recursive=False):
         # type: (Any) -> Optional[str]
         """
         Return the step reference. For example "${step1.parameters.Args/param}"
         :param value: string
+        :param recursive: if True, recursively parse all values in the dict, list or tuple
         :return:
         """
         # look for all the step references
@@ -2793,6 +2800,18 @@ class PipelineController(object):
                 if not isinstance(new_val, six.string_types):
                     return new_val
                 updated_value = updated_value.replace(g, new_val, 1)
+
+        # if we have a dict, list or tuple, we need to recursively update the values
+        if recursive:
+            if isinstance(value, dict):
+                updated_value = {}
+                for k, v in value.items():
+                    updated_value[k] = self._parse_step_ref(v, recursive=True)
+            elif isinstance(value, list):
+                updated_value = [self._parse_step_ref(v, recursive=True) for v in value]
+            elif isinstance(value, tuple):
+                updated_value = tuple(self._parse_step_ref(v, recursive=True) for v in value)
+
         return updated_value
 
     def _parse_task_overrides(self, task_overrides):