feat(blocks): add ConcatenateListsBlock for list concatenation

[majiayu000]

Summary

Implements a new block that concatenates two or more lists into a single list.

• Two required inputs (list1, list2) for basic use
• Three optional advanced inputs (list3, list4, list5) for more complex scenarios
• Preserves element order during concatenation
• Outputs both the concatenated result and total element count

Test plan

• Block includes built-in test_input and test_output for automated testing
• Code passes format and lint checks

Fixes #11139

[coderabbitai]

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[qodo-code-review]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🧪 PR contains tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Mutable Defaults The optional inputs use default=[], which can behave as a shared mutable default depending on how the schema layer instantiates/handles defaults. Prefer using a default_factory=list (or equivalent pattern supported by SchemaField) to avoid unintended cross-instance mutation. list3: list[Any] = SchemaField( description="Optional third list to concatenate", default=[], advanced=True, ) list4: list[Any] = SchemaField( description="Optional fourth list to concatenate", default=[], advanced=True, ) list5: list[Any] = SchemaField( description="Optional fifth list to concatenate", default=[], advanced=True, ) Input Optionality The fields list3-list5 are described as optional but are typed as required list[Any] with an empty-list default. If callers explicitly pass null/None (e.g., via JSON), list(None) will raise. Consider typing as list[Any] | None and normalizing to [] (or ensuring the schema forbids None) to make “optional” behavior robust. list3: list[Any] = SchemaField( description="Optional third list to concatenate", default=[], advanced=True, ) list4: list[Any] = SchemaField( description="Optional fourth list to concatenate", default=[], advanced=True, ) list5: list[Any] = SchemaField( description="Optional fifth list to concatenate", default=[], advanced=True, ) class Output(BlockSchemaOutput): concatenated_list: list[Any] = SchemaField( description="The concatenated list containing all input list elements" ) total_length: int = SchemaField( description="The total number of elements in the concatenated list" ) def __init__(self): super().__init__( id="a1b2c3d4-5e6f-7a8b-9c0d-1e2f3a4b5c6d", description="Concatenates two or more lists into a single list, preserving element order", categories={BlockCategory.BASIC}, input_schema=ConcatenateListsBlock.Input, output_schema=ConcatenateListsBlock.Output, test_input={"list1": [1, 2, 3], "list2": [4, 5, 6]}, test_output=[ ("concatenated_list", [1, 2, 3, 4, 5, 6]), ("total_length", 6), ], ) async def run(self, input_data: Input, **kwargs) -> BlockOutput: result = ( list(input_data.list1) + list(input_data.list2) + list(input_data.list3) + list(input_data.list4) + list(input_data.list5) ) Efficiency/Clarity Concatenation currently creates multiple intermediate lists and repeatedly copies. Consider using itertools.chain (or a loop with extend) to reduce intermediate allocations and simplify future expansion to more than five lists. async def run(self, input_data: Input, **kwargs) -> BlockOutput: result = ( list(input_data.list1) + list(input_data.list2) + list(input_data.list3) + list(input_data.list4) + list(input_data.list5) )