Refuse RGB units only for requests that name their channels (Spec §8): mask-only features on RGB slides

src/morphobricks_preprocessing/run_inputs_request.py

@@ -514,7 +514,12 @@ def unchecked_refusal(mask_id: str, unchecked: Iterable[str], total: int) -> Ref
 
 
 def rgb_refusal(capabilities: Capabilities, rgb_images: Iterable[str]) -> Refusal | None:
-    """Return ``A_RGB_NOT_SUPPORTED`` when ``rgb`` units are requested without the capability."""
+    """Return ``A_RGB_NOT_SUPPORTED`` when ``rgb`` units are requested without the capability.
+
+    ``rgb_images`` are the images of ``rgb`` units whose channels the request names (experiment-v1
+    §8: the refusal applies to a request that includes an RGB unit's channels); a mask-only request
+    names none, so it is never refused for RGB.
+    """
     images = tuple(sorted(rgb_images))
     if not images or capabilities.rgb_support:
         return None

src/morphobricks_preprocessing/run_inputs_resolve.py

@@ -113,7 +113,9 @@ def resolve_request(self, request: Request) -> ResolvedRequest:
             found, more = self._mask(mask, description, fovs, repeats, masks_table)
             refusals.extend(found)
             covered.extend(more)
-        rgb = [f.relative_path for f in fovs if f.image_type == RGB]
+        # A mask-only request names no channel: never refused for RGB (§8 A_RGB_NOT_SUPPORTED).
+        asked = set(request.channel_ids)
+        rgb = [f.relative_path for f in fovs if f.image_type == RGB and asked & set(f.channel_ids)]
         refusals.extend(_some(rgb_refusal(request.capabilities, rgb)))
         refusals.extend(_some(volume_refusal(request)))
         selections = () if refusals else self._selections(request, description, fovs)

tests/test_spec_resolve_request.py

@@ -295,6 +295,20 @@ def test_v28_rgb_units_are_refused_unless_the_consumer_declares_rgb_support(tmp_
     assert accepted.selections[0].channel_indices == (0, 1, 2)
 
 
+@pytest.mark.parametrize("channels", [(), ("G",)])
+def test_v28_only_a_request_naming_rgb_channels_needs_rgb_support(tmp_path, channels):
+    """experiment-v1 §8: A_RGB_NOT_SUPPORTED is for a request naming an RGB unit's channels.
+
+    A mask-only request (no channel) is accepted for any consumer; naming one of R, G, B is not.
+    """
+    inputs, _ = _open(tmp_path, "v28")
+    resolved = inputs.resolve_request(Request(channels))
+    if channels:
+        assert _codes(resolved) == [("A_RGB_NOT_SUPPORTED", "rgb")]
+    else:
+        assert not resolved.refused and len(resolved.selections) == 32
+
+
 def test_v01_channel_units_are_channels_and_need_no_capability(tmp_path):
     inputs, _ = _open(tmp_path, "v01")
     resolved = inputs.resolve_request(Request(("DNA",)))