YAML deserialization error in `OutputAdapter` when using `List`

[oryx1729]

Describe the bug YAML deserialization fails for OutputAdapter when using List in the output_type parameter. Here's an example:

from haystack import Pipeline

pipeline_yaml = """
components:
  output_adapter:
    type: haystack.components.converters.output_adapter.OutputAdapter
    init_parameters:
      output_type: "List[str]"
      template: "{{ test }}"
"""

Pipeline.loads(pipeline_yaml)

Error message

Traceback (most recent call last):
  File "../haystack/haystack/core/pipeline/base.py", line 186, in from_dict
    instance = component_from_dict(component_class, component_data, name, callbacks)
  File "../haystack/haystack/core/serialization.py", line 118, in component_from_dict
    return do_from_dict()
  File "../haystack/haystack/core/serialization.py", line 113, in do_from_dict
    return cls.from_dict(data)
  File "../haystack/haystack/components/converters/output_adapter.py", line 141, in from_dict
    init_params["output_type"] = deserialize_type(init_params["output_type"])
  File "../haystack/haystack/utils/type_serialization.py", line 117, in deserialize_type
    main_type = deserialize_type(main_type_str)
  File "/Users/tanaysoni/haystack/haystack/utils/type_serialization.py", line 142, in deserialize_type
    raise DeserializationError(f"Could not locate the type: {type_name} in the module: {module_name}")
haystack.core.errors.DeserializationError: Could not locate the type: List in the module: builtins

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "../haystack/script.py", line 22, in <module>
    Pipeline.loads(pipeline_yaml)
  File "../haystack/haystack/core/pipeline/base.py", line 258, in loads
    return cls.from_dict(deserialized_data, callbacks)
  File "../haystack/haystack/core/pipeline/base.py", line 195, in from_dict
    raise DeserializationError(msg) from e
haystack.core.errors.DeserializationError: Couldn't deserialize component 'output_adapter' of class 'OutputAdapter' with the following data: {'type': 'haystack.components.converters.output_adapter.OutputAdapter', 'init_parameters': {'output_type': 'List[str]', 'template': '{{ test }}'}}. Possible reasons include malformed serialized data, mismatch between the serialized component and the loaded one (due to a breaking change, see https://github.com/deepset-ai/haystack/releases), etc.

Expected behavior A clear and concise description of what you expected to happen.

Additional context Add any other context about the problem here, like document types / preprocessing steps / settings of reader etc.

To Reproduce Steps to reproduce the behavior

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System:

• OS:
• GPU/CPU:
• Haystack version (commit or version number):
• DocumentStore:
• Reader:
• Retriever:

[vblagoje]

@oryx1729 would you please try using typing.List[str] i.e. the full class name. That should work, see https://github.com/deepset-ai/haystack/pull/8196 for more details. Let us know 🙏

[sjrl]

Yeah here is an example that worked for me in the past @oryx1729

adapter = OutputAdapter.from_dict(
    {
        'type': 'haystack.components.converters.output_adapter.OutputAdapter',
        'init_parameters':
        {
            'template': "\n{% set ns = namespace(doc_string='\n\n') %}\n{% for document in documents %}\n    {% set ns.doc_string = ns.doc_string + '[' + loop.index|string + ']: ' + document.meta.name + '\n' %}\n{% endfor %}\n{% set answer = [replies[0] + ns.doc_string] %}\n{{ answer }}\n",
            'output_type': 'typing.List[str]',
            'custom_filters': {}
        }
     }
)

[vblagoje]

Ok thanks @sjrl - I added a unit test just to have this use case one covered @oryx1729

[vblagoje]

Added a unit test, closing.