fix(handler): set an empty list for aliases with no handlers

pollination_dsl/alias/inputs.py

@@ -4,7 +4,7 @@
  DAGIntegerInputAlias, DAGNumberInputAlias, DAGBooleanInputAlias, \
  DAGJSONObjectInputAlias, DAGArrayInputAlias, DAGFileInputAlias, \
  DAGFolderInputAlias, DAGPathInputAlias, DAGLinkedInputAlias
-from queenbee.base.basemodel import BaseModel, Field
+from queenbee.base.basemodel import BaseModel, Field, validator
 from queenbee.io.common import ItemType, IOAliasHandler
 
 
@@ -39,11 +39,16 @@ class _InputAliasBase(BaseModel):
  'value can be any strings as long as it has been agreed between client-side '
  'developer and author of the recipe.'
  )
+
  handler: List[IOAliasHandler] = Field(
- ...,
+ None,
  description='List of process actions to process the input or output value.'
  )
 
+ @validator('handler', always=True)
+ def create_empty_list(cls, v):
+ return [] if v is None else v
+
  @property
  def required(self):
  if self.optional:

pollination_dsl/alias/outputs.py

@@ -8,7 +8,7 @@
  DAGFileOutputAlias, DAGPathOutputAlias, DAGJSONObjectOutputAlias,
  DAGArrayOutputAlias, DAGLinkedOutputAlias
 )
-from queenbee.base.basemodel import BaseModel
+from queenbee.base.basemodel import BaseModel, validator
 from queenbee.io.common import ItemType, IOAliasHandler
 
 from pydantic import Field
@@ -59,10 +59,14 @@ class _OutputAliasBase(BaseModel):
  )
 
  handler: List[IOAliasHandler] = Field(
- ...,
+ None,
  description='List of process actions to process the input or output value.'
  )
 
+ @validator('handler', always=True)
+ def create_empty_list(cls, v):
+ return [] if v is None else v
+
  @property
  def required(self):
  if self.optional: