feat - add a new endpoint get_tokenizer_info to provide tokenizer/chat-template information (#20575)

Signed-off-by: m-misiura <mmisiura@redhat.com>

tests/entrypoints/openai/test_tokenization.py

@@ -32,6 +32,7 @@ def server(zephyr_lora_added_tokens_files: str):  # noqa: F811
         f"zephyr-lora2={zephyr_lora_added_tokens_files}",
         "--max-lora-rank",
         "64",
+        "--enable-tokenizer-info-endpoint",
     ]
 
     with RemoteOpenAIServer(MODEL_NAME, args) as remote_server:
@@ -283,3 +284,106 @@ async def test_detokenize(
     response.raise_for_status()
 
     assert response.json() == {"prompt": prompt}
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    "model_name,tokenizer_name",
+    [(MODEL_NAME, MODEL_NAME), ("zephyr-lora2", "zephyr-lora2")],
+    indirect=["tokenizer_name"],
+)
+async def test_tokenizer_info_basic(
+    server: RemoteOpenAIServer,
+    model_name: str,
+    tokenizer_name: str,
+):
+    """Test basic tokenizer info endpoint functionality."""
+    response = requests.get(server.url_for("tokenizer_info"))
+    response.raise_for_status()
+    result = response.json()
+    assert "tokenizer_class" in result
+    assert isinstance(result["tokenizer_class"], str)
+    assert result["tokenizer_class"]
+
+
+@pytest.mark.asyncio
+async def test_tokenizer_info_schema(server: RemoteOpenAIServer):
+    """Test that the response matches expected schema types."""
+    response = requests.get(server.url_for("tokenizer_info"))
+    response.raise_for_status()
+    result = response.json()
+    field_types = {
+        "add_bos_token": bool,
+        "add_prefix_space": bool,
+        "clean_up_tokenization_spaces": bool,
+        "split_special_tokens": bool,
+        "bos_token": str,
+        "eos_token": str,
+        "pad_token": str,
+        "unk_token": str,
+        "chat_template": str,
+        "errors": str,
+        "model_max_length": int,
+        "additional_special_tokens": list,
+        "added_tokens_decoder": dict,
+    }
+    for field, expected_type in field_types.items():
+        if field in result and result[field] is not None:
+            assert isinstance(
+                result[field],
+                expected_type), (f"{field} should be {expected_type.__name__}")
+
+
+@pytest.mark.asyncio
+async def test_tokenizer_info_added_tokens_structure(
+    server: RemoteOpenAIServer, ):
+    """Test added_tokens_decoder structure if present."""
+    response = requests.get(server.url_for("tokenizer_info"))
+    response.raise_for_status()
+    result = response.json()
+    added_tokens = result.get("added_tokens_decoder")
+    if added_tokens:
+        for token_id, token_info in added_tokens.items():
+            assert isinstance(token_id, str), "Token IDs should be strings"
+            assert isinstance(token_info, dict), "Token info should be a dict"
+            assert "content" in token_info, "Token info should have content"
+            assert "special" in token_info, (
+                "Token info should have special flag")
+            assert isinstance(token_info["special"],
+                              bool), ("Special flag should be boolean")
+
+
+@pytest.mark.asyncio
+async def test_tokenizer_info_consistency_with_tokenize(
+    server: RemoteOpenAIServer, ):
+    """Test that tokenizer info is consistent with tokenization endpoint."""
+    info_response = requests.get(server.url_for("tokenizer_info"))
+    info_response.raise_for_status()
+    info = info_response.json()
+    tokenize_response = requests.post(
+        server.url_for("tokenize"),
+        json={
+            "model": MODEL_NAME,
+            "prompt": "Hello world!"
+        },
+    )
+    tokenize_response.raise_for_status()
+    tokenize_result = tokenize_response.json()
+    info_max_len = info.get("model_max_length")
+    tokenize_max_len = tokenize_result.get("max_model_len")
+    if info_max_len and tokenize_max_len:
+        assert info_max_len >= tokenize_max_len, (
+            "Info max length should be >= tokenize max length")
+
+
+@pytest.mark.asyncio
+async def test_tokenizer_info_chat_template(server: RemoteOpenAIServer):
+    """Test chat template is properly included."""
+    response = requests.get(server.url_for("tokenizer_info"))
+    response.raise_for_status()
+    result = response.json()
+    chat_template = result.get("chat_template")
+    if chat_template:
+        assert isinstance(chat_template,
+                          str), ("Chat template should be a string")
+        assert chat_template.strip(), "Chat template should not be empty"