Fix TFLite and Coral backend metadata JSON serialization

.github/workflows/backend-metadata.yml

@@ -0,0 +1,17 @@
+name: Backend metadata regression
+on:
+  pull_request:
+  push:
+    branches: [main]
+permissions:
+  contents: read
+jobs:
+  metadata:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+      - run: pip install 'numpy<2' tflite-runtime==2.14.0 fastapi pillow
+      - run: python -m unittest discover -s tests -p test_backend_model_info.py -v

backends/edgetpu/backend.py

@@ -601,7 +601,7 @@ def get_model_info(self) -> Dict[str, Any]:
             "model_type": self.model_type,
             "model_path": self.model_path,
             "labels_path": self.labels_path,
-            "input_shape": list(self.input_shape),
+            "input_shape": [int(dimension) for dimension in self.input_shape],
             "num_labels": len(self.labels),
             "default_confidence_threshold": self.confidence_threshold,
             "device": self.device or "auto",

backends/tflite/backend.py

@@ -273,7 +273,7 @@ def get_model_info(self) -> Dict[str, Any]:
             "backend": "tflite",
             "model_path": self.model_path,
             "labels_path": self.labels_path,
-            "input_shape": list(self.input_shape),
+            "input_shape": [int(dimension) for dimension in self.input_shape],
             "num_labels": len(self.labels),
             "default_confidence_threshold": self.confidence_threshold
         }

tests/test_backend_model_info.py

@@ -0,0 +1,32 @@
+"""Backend discovery must serialize NumPy-shaped TFLite metadata as JSON."""
+import json
+import unittest
+
+import numpy as np
+from fastapi.encoders import jsonable_encoder
+
+from backends.tflite.backend import TFLiteBackend
+from backends.edgetpu.backend import EdgeTPUBackend
+
+
+class ModelInfoTest(unittest.TestCase):
+    def test_numpy_dimensions_are_json_serializable_without_hardware(self):
+        for cls in (TFLiteBackend, EdgeTPUBackend):
+            with self.subTest(backend=cls.__name__):
+                # Metadata requires neither an interpreter nor a physical Coral.
+                backend = object.__new__(cls)
+                backend.model_path = "model.tflite"
+                backend.labels_path = "labels.txt"
+                backend.input_shape = np.array([1, 300, 300, 3], dtype=np.int32)
+                backend.labels = ["person"]
+                backend.confidence_threshold = 0.5
+                backend.model_type = "ssd"
+                backend.device = "usb"
+                backend.requires_int8 = False
+                info = backend.get_model_info()
+                self.assertEqual(json.loads(json.dumps(info))["input_shape"], [1, 300, 300, 3])
+                self.assertEqual(jsonable_encoder(info)["input_shape"], [1, 300, 300, 3])
+
+
+if __name__ == "__main__":
+    unittest.main()