support chat generator as input of TextGenerationPipeline (#35551)

* support chat generator as input of TextGenerationPipeline

* missing import

* fix tests

* again

* simpler

* add test

src/transformers/pipelines/text_generation.py

@@ -1,4 +1,6 @@
 import enum
+import itertools
+import types
 import warnings
 from typing import Dict
 
@@ -260,16 +262,27 @@ def __call__(self, text_inputs, **kwargs):
               ids of the generated text.
         """
         if isinstance(
-            text_inputs, (list, tuple, KeyDataset) if is_torch_available() else (list, tuple)
-        ) and isinstance(text_inputs[0], (list, tuple, dict)):
-            # We have one or more prompts in list-of-dicts format, so this is chat mode
-            if isinstance(text_inputs[0], dict):
-                return super().__call__(Chat(text_inputs), **kwargs)
+            text_inputs,
+            (list, tuple, types.GeneratorType, KeyDataset)
+            if is_torch_available()
+            else (list, tuple, types.GeneratorType),
+        ):
+            if isinstance(text_inputs, types.GeneratorType):
+                text_inputs, _ = itertools.tee(text_inputs)
+                text_inputs, first_item = (x for x in text_inputs), next(_)
             else:
-                chats = [Chat(chat) for chat in text_inputs]  # 🐈 🐈 🐈
-                return super().__call__(chats, **kwargs)
-        else:
-            return super().__call__(text_inputs, **kwargs)
+                first_item = text_inputs[0]
+            if isinstance(first_item, (list, tuple, dict)):
+                # We have one or more prompts in list-of-dicts format, so this is chat mode
+                if isinstance(first_item, dict):
+                    return super().__call__(Chat(text_inputs), **kwargs)
+                else:
+                    chats = (Chat(chat) for chat in text_inputs)  # 🐈 🐈 🐈
+                    if isinstance(text_inputs, types.GeneratorType):
+                        return super().__call__(chats, **kwargs)
+                    else:
+                        return super().__call__(list(chats), **kwargs)
+        return super().__call__(text_inputs, **kwargs)
 
     def preprocess(
         self,

tests/pipelines/test_pipelines_text_generation.py

@@ -292,6 +292,50 @@ def __getitem__(self, i):
                 ],
             )
 
+    @require_torch
+    def test_small_chat_model_with_iterator_pt(self):
+        from transformers.pipelines.pt_utils import PipelineIterator
+
+        text_generator = pipeline(
+            task="text-generation", model="hf-internal-testing/tiny-gpt2-with-chatml-template", framework="pt"
+        )
+
+        # Using `do_sample=False` to force deterministic output
+        chat1 = [
+            {"role": "system", "content": "This is a system message."},
+            {"role": "user", "content": "This is a test"},
+        ]
+        chat2 = [
+            {"role": "system", "content": "This is a system message."},
+            {"role": "user", "content": "This is a second test"},
+        ]
+        expected_chat1 = chat1 + [
+            {
+                "role": "assistant",
+                "content": " factors factors factors factors factors factors factors factors factors factors",
+            }
+        ]
+        expected_chat2 = chat2 + [
+            {
+                "role": "assistant",
+                "content": " stairs stairs stairs stairs stairs stairs stairs stairs stairs stairs",
+            }
+        ]
+
+        def data():
+            yield from [chat1, chat2]
+
+        outputs = text_generator(data(), do_sample=False, max_new_tokens=10)
+        assert isinstance(outputs, PipelineIterator)
+        outputs = list(outputs)
+        self.assertEqual(
+            outputs,
+            [
+                [{"generated_text": expected_chat1}],
+                [{"generated_text": expected_chat2}],
+            ],
+        )
+
     @require_tf
     def test_small_model_tf(self):
         text_generator = pipeline(task="text-generation", model="sshleifer/tiny-ctrl", framework="tf")