Add Tuple support

src/transformers/utils/chat_template_utils.py

@@ -239,13 +239,24 @@ def _parse_type_hint(hint):
                 return_dict["nullable"] = True
             return return_dict
         elif origin is tuple:
-            raise ValueError(
-                "This helper does not parse Tuple types, as they are usually used to indicate that "
-                "each position is associated with a specific type, and this requires JSON schemas "
-                "that are not supported by most templates. We recommend "
-                "either using List instead for arguments where this is appropriate, or "
-                "splitting arguments with Tuple types into multiple arguments that take single inputs."
-            )
+            if not get_args(hint):
+                return {"type": "array"}
+            if len(get_args(hint)) == 1:
+                raise ValueError(
+                    "Tuple type hints should only be used when the argument has a fixed length and each "
+                    f"element has a specific type. The hint {hint} indicates a Tuple of length 1. "
+                    "This should be replaced with an unwrapped type hint instead like "
+                    f"{get_args(hint)[0]}. Alternatively, if the "
+                    "function can actually take a tuple with multiple elements, please either indicate "
+                    f"each element type (e.g. Tuple[{get_args(hint)[0]}, {get_args(hint)[0]}]), "
+                    f"or if the input can be variable length, use List[{get_args(hint)[0]}] instead."
+                )
+            if ... in get_args(hint):
+                raise ValueError(
+                    "'...' is not supported in Tuple type hints. Use List[] types for variable-length"
+                    " inputs instead."
+                )
+            return {"type": "array", "prefixItems": [_parse_type_hint(t) for t in get_args(hint)]}
         elif origin is dict:
             # The JSON equivalent to a dict is 'object', which mandates that all keys are strings
             # However, we can specify the type of the dict values with "additionalProperties"

tests/utils/test_chat_template_utils.py

@@ -1,5 +1,5 @@
 import unittest
-from typing import List, Optional, Union
+from typing import List, Optional, Tuple, Union
 
 from transformers.utils import get_json_schema
 
@@ -234,9 +234,10 @@ def fn(x: int) -> int:
             "description": "Test function",
             "parameters": {
                 "type": "object",
-                "properties": {"x": {"type": "integer", "description": "The input"}, "return": {"type": "integer"}},
+                "properties": {"x": {"type": "integer", "description": "The input"}},
                 "required": ["x"],
             },
+            "return": {"type": "integer"},
         }
         self.assertEqual(schema, expected_schema)
 
@@ -254,17 +255,83 @@ def fn(x: int) -> int:
             """
             return x
 
+        schema = get_json_schema(fn)
+        expected_schema = {
+            "name": "fn",
+            "description": "Test function",
+            "parameters": {
+                "type": "object",
+                "properties": {"x": {"type": "integer", "description": "The input"}},
+                "required": ["x"],
+            },
+            "return": {"type": "integer", "description": "The output"},
+        }
+        self.assertEqual(schema, expected_schema)
+
+    def test_tuple(self):
+        def fn(x: Tuple[int, str]):
+            """
+            Test function
+
+            Args:
+                x: The input
+
+
+            Returns:
+                The output
+            """
+            return x
+
         schema = get_json_schema(fn)
         expected_schema = {
             "name": "fn",
             "description": "Test function",
             "parameters": {
                 "type": "object",
                 "properties": {
-                    "x": {"type": "integer", "description": "The input"},
-                    "return": {"type": "integer", "description": "The output"},
+                    "x": {
+                        "type": "array",
+                        "prefixItems": [{"type": "integer"}, {"type": "string"}],
+                        "description": "The input",
+                    }
                 },
                 "required": ["x"],
             },
         }
         self.assertEqual(schema, expected_schema)
+
+    def test_single_element_tuple_fails(self):
+        def fn(x: Tuple[int]):
+            """
+            Test function
+
+            Args:
+                x: The input
+
+
+            Returns:
+                The output
+            """
+            return x
+
+        # Single-element tuples should just be the type itself, or List[type] for variable-length inputs
+        with self.assertRaises(ValueError):
+            get_json_schema(fn)
+
+    def test_ellipsis_type_fails(self):
+        def fn(x: Tuple[int, ...]):
+            """
+            Test function
+
+            Args:
+                x: The input
+
+
+            Returns:
+                The output
+            """
+            return x
+
+        # Variable length inputs should be specified with List[type], not Tuple[type, ...]
+        with self.assertRaises(ValueError):
+            get_json_schema(fn)