[1fanwang]

Tracking issue

Related to flyteorg/flyte#6473.

Why are the changes needed?

A local workflow cannot check whether an indexed list entry is None. It raises an error instead of selecting a branch:

AttributeError: 'NoneType' object has no attribute 'union'

What changes were proposed in this pull request?

When a local workflow compares an indexed value, such as the first item in a task's list output, the comparison now looks that item up before checking it. The lookup runs on a copy, so other uses of the same output keep their original value. A workflow that is only being compiled has no values yet, so its references to indexed items are left as written.

How was this patch tested?

Testing Done

The same local CLI path now selects the expected branch without a remote Flyte cluster.

Scenario	Command	Result
Indexed optional entry	pyflyte run indexed_none_repro.py wf	Task succeeded

Reproducer source: indexed_none_repro.py

from flytekit import conditional, task, workflow
from flytekit.core.task import Echo

echo: Echo = Echo(name="branch_result", inputs={"value": str})


@task
def check_status() -> list[bool | None]:
    return [None, True]


@workflow
def wf() -> str:
    status = check_status()[0]
    return (
        conditional("status_check")
        .if_(status.is_none())
        .then(echo(value="Task succeeded"))
        .else_()
        .then(echo(value="Task failed"))
    )

pyflyte run indexed_none_repro.py wf

Running Execution on local.
Task succeeded
exit_code=0

The original failing comparison used d69b3fb:

Running Execution on local.
AttributeError: 'NoneType' object has no attribute 'union'
exit_code=1

Setup process

Python 3.12 with the SDK development environment and this checkout on PYTHONPATH.

Screenshots

Not applicable.

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

The documented API is unchanged.

Related PRs

None.

Docs link

No separate documentation change.