fix: accept long JSON strings in ChatTemplateConfig.from_json

lmdeploy/model.py

@@ -92,16 +92,14 @@ def to_json(self, file_path=None):
     @classmethod
     def from_json(cls, file_or_string):
         """Construct a dataclass instance from a JSON file or JSON string."""
-        try:
-            # Try to open the input_data as a file path
+        if os.path.isfile(file_or_string):
             with open(file_or_string, encoding='utf-8') as file:
                 json_data = file.read()
-        except FileNotFoundError:
-            # If it's not a file path, assume it's a JSON string
+        else:
+            # If it's not a file path, assume it's a JSON string. Opening it
+            # as a path may fail with errors other than FileNotFoundError,
+            # e.g. a name longer than the OS limit, or quotes on Windows.
             json_data = file_or_string
-        except OSError:
-            # If it's not a file path and not a valid JSON string, raise error
-            raise ValueError('Invalid input. Must be a file path or a valid JSON string.')
         json_data = json.loads(json_data)
         if json_data.get('model_name', None) is None:
             json_data['model_name'] = random_uuid()

tests/test_lmdeploy/test_model.py

@@ -87,6 +87,21 @@ def test_base_model():
     assert model.messages2prompt('test') == 'test'
 
 
+def test_chat_template_config_from_json(tmp_path):
+    import json
+
+    from lmdeploy.model import ChatTemplateConfig
+
+    # A long meta instruction makes the string invalid as a file name.
+    config = dict(model_name='from-json-test', meta_instruction='You are a helpful assistant. ' * 12)
+    json_str = json.dumps(config)
+    assert ChatTemplateConfig.from_json(json_str).meta_instruction == config['meta_instruction']
+
+    json_file = tmp_path / 'chat_template.json'
+    json_file.write_text(json_str, encoding='utf-8')
+    assert ChatTemplateConfig.from_json(str(json_file)).meta_instruction == config['meta_instruction']
+
+
 def test_vicuna():
     prompt = 'hello, can u introduce yourself'
     model = MODELS.get('vicuna')(capability='completion')