Fix mutable_flow test flow passing a stale second argument to extract_step_decorator_from_decospec

[Anai-Guo]

extract_step_decorator_from_decospec accepts exactly one argument
(metaflow/decorators.py:692):

def extract_step_decorator_from_decospec(decospec: str):

but both call sites in the mutable_flow test flow still pass a second
positional {}:

# test/test_config/mutable_flow.py:61  (ModifyFlow.mutate)
env_deco, _ = extract_step_decorator_from_decospec(decos[0], {})

# test/test_config/mutable_flow.py:110 (ModifyFlow2.mutate)
env_deco, _ = extract_step_decorator_from_decospec(deco, {})

Both are reached from a FlowMutator.mutate(), which runs at flow-definition
time, so mutable_flow.py raises TypeError: extract_step_decorator_from_decospec() takes 1 positional argument but 2 were given before any step executes. The flow
is registered as a test case in test/test_config/test.py:96.

The two call sites in library code already pass a single argument, which is what
makes this a stale-caller bug rather than a signature question:

Call site	Args	Status
metaflow/decorators.py:768	1	✅
metaflow/user_decorators/mutable_step.py:340	1	✅
test/test_config/mutable_flow.py:61	2	❌
test/test_config/mutable_flow.py:110	2	❌

Binding the real upstream signature against all four call sites, with the two
library callers as the control group:

extract_step_decorator_from_decospec (decospec)
  TypeError test/test_config/mutable_flow.py:61  (decos[0], {}) -> too many positional arguments
  TypeError test/test_config/mutable_flow.py:110 (deco, {})     -> too many positional arguments
  OK        CONTROL metaflow/decorators.py:768
  OK        CONTROL metaflow/user_decorators/mutable_step.py:340

This PR drops the extra {} at both sites so the test flow matches the
signature and the two library callers. Nothing else changes — the return value
is still unpacked as (step_deco, has_args_kwargs), exactly as
mutable_step.py:340 does.

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

This PR fixes the mutable-flow configuration test by removing obsolete second arguments from two calls to extract_step_decorator_from_decospec.

• Aligns both test-flow call sites with the helper’s single-argument signature.
• Preserves the existing decorator parsing and return-value handling.

Confidence Score: 5/5

The PR appears safe to merge; the narrowly scoped changes correct two stale test call sites without altering behavior beyond preventing their argument-count errors.

Both modified calls now match the parser’s single-argument signature while retaining the same inputs, tuple unpacking, and subsequent decorator mutation logic.

Important Files Changed

Filename	Overview
test/test_config/mutable_flow.py	Both stale two-argument calls are correctly updated to use the helper’s existing single-argument interface, with no issues identified.

_{Reviews (1): Last reviewed commit: "fix(test_config): drop the stale second ..." | Re-trigger Greptile}

[Shriprasad-P]

The extra {} is definitely stale, but I don't think removing it is sufficient to make this flow work against the current mutable-step API.

MutableStep.decorator_specs now yields (name, fq_name, args, kwargs) tuples. These two paths still call .startswith("environment:") on those values, so they can fail before extract_step_decorator_from_decospec() is reached.

There are a couple of related stale API usages here as well: the decorator attributes are already available from the tuple, and add_decorator() now expects them through deco_kwargs= (with duplicates=OVERRIDE when replacing the existing environment decorator).

The current implementation in test/ux/core/flows/config/mutable_flow.py already follows that pattern. I think test/test_config/mutable_flow.py should be aligned with that implementation rather than continuing to parse these specs through extract_step_decorator_from_decospec.

So the arity change itself is correct, but the test flow still appears incompatible with the current decorator-spec API.