fix: filter_long_prompt crashes on chat-templated multimodal prompts

slime/utils/data.py

@@ -111,11 +111,10 @@ def filter_long_prompt(origin_samples: list[Sample], tokenizer, processor, max_l
                 if len(input_ids) <= max_length:
                     kept.append((position, sample))
         if multimodal:
-            from slime.utils.processing_utils import process_vision_info
-
             for position, sample in multimodal:
-                multimodal_inputs = process_vision_info(sample.prompt, processor)
-                processor_output = processor(text=sample.prompt, **multimodal_inputs)
+                # sample.prompt is already chat-templated text, so reuse the media
+                # Dataset.__init__ parsed from the message list.
+                processor_output = processor(text=sample.prompt, **sample.multimodal_inputs)
                 input_ids = processor_output["input_ids"][0]
                 if len(input_ids) <= max_length:
                     kept.append((position, sample))

tests/test_filter_long_prompt.py

@@ -25,19 +25,6 @@
 NUM_GPUS = 0
 
 
-@pytest.fixture
-def stub_process_vision_info(monkeypatch):
-    """`slime.utils.processing_utils` pulls in transformers + PIL.
-
-    The multimodal branch imports it lazily, and only `process_vision_info` is
-    needed here, so stub the module rather than requiring transformers on the
-    CPU image.
-    """
-    module = types.ModuleType("slime.utils.processing_utils")
-    module.process_vision_info = lambda prompt, processor: {"images": None}
-    monkeypatch.setitem(sys.modules, "slime.utils.processing_utils", module)
-
-
 class _Tokenizer:
     """Batched tokenizer stand-in: prompt "pN:len" tokenizes to `len` ids."""
 
@@ -67,7 +54,7 @@ def _make_samples(specs):
 
 
 @pytest.mark.unit
-def test_preserves_order_when_nothing_is_filtered(stub_process_vision_info):
+def test_preserves_order_when_nothing_is_filtered():
     # Alternating modality, every prompt well under the limit.
     samples = _make_samples([(i % 2 == 0, 5) for i in range(6)])
 
@@ -77,7 +64,7 @@ def test_preserves_order_when_nothing_is_filtered(stub_process_vision_info):
 
 
 @pytest.mark.unit
-def test_preserves_order_when_some_are_filtered(stub_process_vision_info):
+def test_preserves_order_when_some_are_filtered():
     specs = [
         (True, 5),  # p0 multimodal, keep
         (False, 500),  # p1 text-only, drop
@@ -95,7 +82,7 @@ def test_preserves_order_when_some_are_filtered(stub_process_vision_info):
 
 @pytest.mark.unit
 @pytest.mark.parametrize("all_multimodal", [True, False])
-def test_single_modality_batches_are_unchanged(stub_process_vision_info, all_multimodal):
+def test_single_modality_batches_are_unchanged(all_multimodal):
     samples = _make_samples([(all_multimodal, 5)] * 4)
 
     kept = filter_long_prompt(samples, _Tokenizer(), _Processor(), max_length=100)
@@ -112,5 +99,35 @@ def test_no_processor_path_still_preserves_order():
     assert [s.prompt for s in kept] == ["p0:5", "p2:5"]
 
 
+@pytest.mark.unit
+def test_multimodal_length_reuses_parsed_inputs(monkeypatch):
+    """With apply_chat_template, sample.prompt is a string, not a message list.
+
+    Re-parsing it with process_vision_info crashes (the parser expects message
+    dicts), so the media parsed by Dataset.__init__ must be passed through.
+    """
+
+    def reparse(prompt, processor):
+        raise AssertionError("filter_long_prompt re-parsed the chat-templated prompt")
+
+    module = types.ModuleType("slime.utils.processing_utils")
+    module.process_vision_info = reparse
+    monkeypatch.setitem(sys.modules, "slime.utils.processing_utils", module)
+
+    calls = []
+
+    class _RecordingProcessor(_Processor):
+        def __call__(self, text=None, **kwargs):
+            calls.append(kwargs)
+            return super().__call__(text=text)
+
+    samples = _make_samples([(True, 5), (True, 500)])
+
+    kept = filter_long_prompt(samples, _Tokenizer(), _RecordingProcessor(), max_length=100)
+
+    assert [s.prompt for s in kept] == ["p0:5"]
+    assert calls == [{"images": ["img"]}, {"images": ["img"]}]
+
+
 if __name__ == "__main__":
     raise SystemExit(pytest.main([__file__]))