[APO-2731] Filter undefined values from subworkflow inputs

[devin-ai-integration]

Fixes an issue where subworkflow deployments with optional inputs whose dependencies resolve to undefined were raising INVALID_INPUTS errors instead of executing seamlessly using default values. The fix filters out undefined values (in addition to None) in the input compilation methods for SubworkflowDeploymentNode.

Review & Testing Checklist for Human

• Verify the test test_compile_subworkflow_inputs__undefined_input_filtered fails on main (produces 2 inputs with undefined serialized as empty string) and passes on this branch (produces 1 input with undefined filtered out)
• Confirm filtering undefined values doesn't break existing subworkflow deployment functionality
• Consider if there are other code paths in the SDK that might need similar undefined filtering

Test Plan

1. Run pytest src/vellum/workflows/nodes/displayable/subworkflow_deployment_node/tests/test_node.py::test_compile_subworkflow_inputs__undefined_input_filtered -xvs on this branch - should pass
2. Checkout main and run the same test - should fail with "Expected 1 input, got 2"

Notes

• Requested by: @dvargas92495
• Session: https://app.devin.ai/sessions/6321a3e71cc34708bd6cbeafd3ed643e

[devin-ai-integration]

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[dvargas92495]

DevinAI remove this test and associated implementation, we want to focus on the deployment variants

[dvargas92495]

DevinAI remove this input from being defined

[dvargas92495]

DevinAI we want to mock the pull api so we can test the resolved flow and not the execute_workflow_stream

[dvargas92495]

DevinAI can you run the test you added here against the main branch and show me what happens when you do?

[devin-ai-integration]

I ran the test against main and it passes:

============================= test session starts ==============================
platform linux -- Python 3.9.22, pytest-7.4.4, pluggy-1.6.0
...
vellum/workflows/nodes/displayable/subworkflow_deployment_node/tests/test_resolved_workflow_path.py::test_run_workflow__resolved_workflow_path PASSED
======================= 1 passed, 435 warnings in 0.07s ========================

This means the test currently only proves "resolved workflow path works when the optional input is omitted from the dict" - which already works on main. It does not exercise the undefined filtering scenario from APO-2731.

To actually demonstrate the bug fix, the test would need to create a situation where subworkflow_inputs contains an entry whose value is undefined. Would you like me to:

1. Modify the test to use a BaseInputs instance with an undefined value instead of a raw dict?
2. Find a way to produce undefined through normal workflow dependency resolution (e.g., via merge behaviors)?
3. Keep the test as-is since it at least verifies the resolved path works correctly?

[dvargas92495]

DevinAI I would like you to revert the changes to inputs/base.py and keep iterating on the test until you have something that fails on main

[devin-ai-integration]

I checked the PR diff and commit history - there are no changes to inputs/base.py in this PR. The only files changed are:

• src/vellum/workflows/nodes/displayable/subworkflow_deployment_node/node.py
• src/vellum/workflows/nodes/displayable/subworkflow_deployment_node/tests/test_node.py

I'll now iterate on the test to create one that fails on main. I'll set up a scenario where subworkflow_inputs references an upstream node output that resolves to undefined through normal workflow execution (e.g., via conditional branching or merge behavior).

[devin-ai-integration]

I've updated the test to properly demonstrate the bug fix. The new test test_compile_subworkflow_inputs__undefined_input_filtered:

1. Creates an upstream node with an output that is declared but never set (resolves to undefined)
2. References that output in the subworkflow_inputs dict
3. Verifies that _compile_subworkflow_inputs() filters out the undefined value

On main: The test fails because undefined is serialized as an empty string in a WorkflowRequestJsonInputRequest, resulting in 2 inputs instead of 1.

On this branch: The test passes because undefined values are filtered out, resulting in only 1 input.

This test exercises the actual bug fix in _add_compiled_input which now filters out undefined values before they get serialized for the API call.