Handle missing SheetSage beat grid in short inputs

pipeline.py

@@ -403,7 +403,8 @@ def generate_all(source: str, instrument: str, styles: dict[str, str], seed: int
                     "result_seconds": dict(durations), "drum_hits": drum_count,
                     "yue_requested": include_yue, "yue_timing": dict(yue_timing),
                     "errors": dict(errors), "complete": complete,
-                    "source_timing_preserved": list(SAMPLER_VARIANTS),
+                    "source_timing_preserved": [name for name in SAMPLER_VARIANTS
+                                                if outputs[name]],
                     "bass_transpose_semitones": bass_shift,
                     "bass_source": bass_source,
                     "transcription_source": transcription_source,
@@ -411,7 +412,8 @@ def generate_all(source: str, instrument: str, styles: dict[str, str], seed: int
                     "yue_vocal_absence_guaranteed": False,
                     "elapsed_seconds": round(time.monotonic() - began, 2)}
         return (*(outputs[name] for name in VARIANTS), str(melody_midi),
-                str(drums_midi) if drums_midi else None, str(beat_lab),
+                str(drums_midi) if drums_midi else None,
+                str(beat_lab) if beat_lab.is_file() else None,
                 str(folder / "instrumental-melody.abc"), metadata)
 
     if progress:
@@ -428,7 +430,7 @@ def generate_all(source: str, instrument: str, styles: dict[str, str], seed: int
     try:
         midi, melody_abc, full_abc, beat_lab = transcribe(pcm24, folder, log)
     except RuntimeError as error:
-        if "could not export ABC" not in str(error):
+        if "SheetSage2 could not export" not in str(error) or "ABC" not in str(error):
             raise
         errors["sheet_sage"] = "SheetSage2 не смог записать ноты в ABC"
         midi, melody_abc, full_abc, beat_lab = (
@@ -451,6 +453,8 @@ def generate_all(source: str, instrument: str, styles: dict[str, str], seed: int
         progress(.30, desc="Синтезирую инструмент и барабаны")
     melody_raw, melody_midi = render_instrument(midi, folder, instrument, duration, log)
     try:
+        if not beat_lab.is_file():
+            raise ValueError("SheetSage2 не дал сетку долей; барабаны пропущены")
         drums_raw, drums_midi, drum_count = render_drums(midi, beat_lab, folder,
                                                         duration, log)
         solo_raw, combined_raw = pair_with_drums(melody_raw, drums_raw, folder)

test_sampler.py

@@ -25,7 +25,6 @@ class SamplerTest(unittest.TestCase):
                                 ("empty.mid", "empty.abc", "beat.lab"))
             pretty_midi.PrettyMIDI().write(str(empty))
             abc.write_text("unusable empty melody")
-            beat.write_text("0 1 4 4\n.5 2 4 4\n1 3 4 4\n")
 
             def fake_mp3(_, target, __, **___):
                 target.write_bytes(b"fake mp3")
@@ -46,6 +45,10 @@ class SamplerTest(unittest.TestCase):
             self.assertIn("SheetSage2 не нашёл нот", result[-1]["errors"]["sheet_sage"])
             self.assertEqual(len(pretty_midi.PrettyMIDI(str(empty)).instruments[0].notes), 1)
             self.assertNotIn("Vocal", abc.read_text())
+            self.assertIsNone(result[12])
+            self.assertEqual(result[-1]["errors"]["instrument_drums"],
+                             "SheetSage2 не дал сетку долей; барабаны пропущены")
+            self.assertNotIn("instrument_drums", result[-1]["source_timing_preserved"])
 
     def test_archive_keeps_original_bytes_and_uses_opaque_name(self):
         from pipeline import archive_recording, source_sha256