Accept positional/string context shorthand for Flow.model(context_type=)

ccflow/flow_model.py

@@ -928,6 +928,20 @@ def _generated_model_instance(stage: Any) -> Optional["_GeneratedFlowModelBase"]
     return None
 
 
+def _declared_context_type_for_model(model: CallableModel) -> Optional[Type[ContextBase]]:
+    """Return a generated model's declared ``context_type``, if any.
+
+    Generated ``@Flow.model`` instances expose ``FlowContext`` as their runtime
+    context type but may also declare a nominal ``context_type`` whose ordered
+    fields enable positional/string context shorthand.
+    """
+
+    generated = _generated_model_instance(model)
+    if generated is None:
+        return None
+    return type(generated).__flow_model_config__.declared_context_type
+
+
 def _model_context_contract(
     model: CallableModel,
 ) -> _ModelContextContract:
@@ -1897,6 +1911,17 @@ def _compute_context_from_explicit(model: CallableModel, context: Any, contract:
         if _context_matches_type(context, model.context_type):
             return context
         return _runtime_context_for_model(model, _context_values(context))
+    # Positional/string shorthand (e.g. `[start, end]` or "start,end", as used by
+    # Hydra `+context=[...]`) only carries field *order*, not names. A generated
+    # model's runtime context_type is the open FlowContext bag, which has no declared
+    # fields to zip against, so the shorthand would otherwise be silently dropped.
+    # When the model declares a context_type, validate the shorthand through it first
+    # (which applies the ordered `zip(model_fields, v)` mapping), then forward the
+    # named values into the FlowContext bag. Mappings already carry names and keep
+    # their existing path.
+    declared = _declared_context_type_for_model(model)
+    if declared is not None and not isinstance(context, Mapping):
+        return _runtime_context_for_model(model, _context_values(declared.model_validate(context)))
     return contract.runtime_context_type.model_validate(context)
 
 

ccflow/tests/test_flow_model_context_shorthand.py

@@ -0,0 +1,53 @@
+"""Tests for positional/string context shorthand on ``@Flow.model(context_type=...)``.
+
+Class-based ``CallableModel`` execution already accepts positional/string context
+shorthand (the ordered ``zip(model_fields, v)`` mapping in ``ContextBase``). Generated
+``@Flow.model`` instances expose ``FlowContext`` (the open bag) as their runtime context
+type, so without a declared ``context_type`` there are no ordered fields to zip against.
+When a ``context_type`` is declared, ``compute()`` routes the shorthand through it first.
+
+Scope: this covers the ``compute()`` entry point. The direct-call form (``model([...])``)
+is intentionally not supported here because ``Flow.call`` validates against ``FlowContext``
+before the generated body runs; supporting it would require reverting the bag-of-types
+design.
+"""
+
+from datetime import date
+
+from ccflow import DateRangeContext, Flow, FromContext
+
+
+@Flow.model(context_type=DateRangeContext)
+def span(start_date: FromContext[date], end_date: FromContext[date]) -> int:
+    return (end_date - start_date).days
+
+
+class TestComputeShorthand:
+    def test_list_shorthand(self):
+        assert span().flow.compute(["2025-01-02", "2026-01-01"]).value == 364
+
+    def test_tuple_shorthand(self):
+        assert span().flow.compute(("2025-01-02", "2026-01-01")).value == 364
+
+    def test_string_shorthand(self):
+        assert span().flow.compute("2025-01-02,2026-01-01").value == 364
+
+    def test_named_inputs_still_work(self):
+        assert span().flow.compute(start_date="2025-01-02", end_date="2026-01-01").value == 364
+
+    def test_context_object_still_works(self):
+        ctx = DateRangeContext(start_date=date(2025, 1, 2), end_date=date(2026, 1, 1))
+        assert span().flow.compute(ctx).value == 364
+
+    def test_shorthand_matches_named(self):
+        assert span().flow.compute(["2025-01-02", "2026-01-01"]).value == span().flow.compute(start_date="2025-01-02", end_date="2026-01-01").value
+
+
+class TestNoDeclaredContextTypeUnaffected:
+    def test_bag_model_still_uses_named(self):
+        @Flow.model
+        def bag(start_date: FromContext[date], end_date: FromContext[date]) -> int:
+            return (end_date - start_date).days
+
+        # Without a declared context_type there is no field order; named inputs are required.
+        assert bag().flow.compute(start_date="2025-01-02", end_date="2026-01-01").value == 364