fix(etl-uvicorn): do not require a body when every input field is optional

[badGarnet]

Problem

wrap_in_fastapi chooses its /invoke signature on parameter presence:

if input_schema_model.model_fields:
    async def run_job(request: input_schema_model)   # no default => body REQUIRED
else:
    async def run_job()                              # no body accepted

A pydantic body parameter with no default is mandatory even when every field inside the model is optional. So a plugin whose parameters are all optional gets a required body that no caller has a reason to populate — and before it grew those parameters, that same plugin accepted no body at all. Adding an optional parameter therefore looks backward-compatible while silently flipping the HTTP contract.

Fix

Default the body when the generated input model has no required fields:

body_is_optional = input_schema_model.model_fields and not any(
    field.is_required() for field in input_schema_model.model_fields.values()
)

• all fields optional → request: Optional[input_schema_model] = None; an absent body resolves each field to its own default, which is exactly what the function signature already promises.
• any field required → unchanged, body mandatory. A downloader invoked without file_data still fails validation rather than receiving None.
• no parameters → unchanged, no body accepted.

The handler body is extracted into run_job_with_body so the two model-bearing branches cannot drift.

Testing

make check-version, make check clean; 75 tests pass (5 new).

plugin shape	bodyless	{}	populated
no params	200	200	—
all params optional	200 (was 422)	200	200
any param required	422	422	200

New tests are in test/api/test_api.py. Verified they catch the regression by reverting the fix: test_all_optional_params_accept_absent_or_empty_body[None] fails. The other four are guards against the fix over-reaching — notably test_required_param_still_rejects_an_absent_body, since silently accepting an absent file_data would be worse than the bug being fixed.

Also verified against the real playground indexer served through the patched generator, rather than only synthetic functions:

• bodyless POST → 200, indexes from the settings-file fallback
• populated wire invocation_settings → 200, and takes precedence over the file fallback

That second case is the point: this restores the bodyless contract without reverting the wire-settings capability. Both planes work.

🤖 Generated with Claude Code

[cubic-dev-ai]

All reported issues were addressed across 4 files

<sub>Shadow auto-approve: would not auto-approve because issues were found.

Re-trigger cubic</sub>

[cubic-dev-ai]

0 issues found across 3 files (changes from recent commits).

<sub>Shadow auto-approve: would auto-approve. Fixes a bug where plugins with all-optional parameters incorrectly required a request body, and prevents a 500 when optional file_data is absent. The change is bounded, well-tested, and clearly beneficial.

Re-trigger cubic</sub>