chat : fix yandex chat template (#15116)

Author: CISC

src/llama-chat.cpp

@@ -625,8 +625,6 @@ int32_t llm_chat_apply_template(
     } else if (tmpl == LLM_CHAT_TEMPLATE_YANDEX) {
         // Yandex template ("\n\n" is defined as EOT token)
 
-        ss << "<s>";
-
         for (size_t i = 0; i < chat.size(); i++) {
             std::string role(chat[i]->role);
             if (role == "user") {

tests/test-chat-template.cpp

@@ -277,9 +277,9 @@ int main(void) {
         {
             /* .name= */ "yandex/YandexGPT-5-Lite-8B-instruct",
             /* .template_str= */ "<s>{%- set names = {'assistant': ' Ассистент:', 'user': ' Пользователь:'} %}\n{%- set tools_prefix = 'Тебе доступны следующие функции:' %}\n{%- macro __render_tool(tool) %}\n    {%- set name = tool.function.name %}\n    {%- set description = tool.function.description|default('') %}\n    {%- set parameters = tool.function.parameters|tojson %}\n    {{- '\\n' }}function {{ '{' }}'name':'{{ name }}',\n    {%- if tool.function.description %}'description':'{{ description }}',{% endif %}\n'parameters':{{ parameters }}\n    {{- '}' }}\n{%- endmacro %}\n{%- macro __render_tools(tools) %}\n    {{- tools_prefix }}\n    {%- for tool in tools %}\n        {{- __render_tool(tool) }}\n    {%- endfor %}\n    {{- '\\n\\n' }}\n{%- endmacro %}\n{%- macro __render_tool_message(message) %}\n    {{- '\\n\\nРезультат вызова' }} {{ message.name }}: {{ message.content }} {{ '\\n\\n' }}\n{%- endmacro %}\n{%- if tools -%}\n    {{- __render_tools(tools) }}\n{%- endif -%}\n{%- macro __render_user_message(message) %}\n{{ names.user }} {{ message.content + '\\n\\n' }}\n{%- endmacro %}\n{%- macro __render_assistant_message(message) %}\n    {{- names.assistant }}\n    {%- set call = message['function_call'] %}\n    {%- if call %}\n        {{- '\\n[TOOL_CALL_START]' }}{{ call.name }}{{ '\\n' }}{{ call.arguments|tojson }}\n    {%- else %}\n        {{- ' ' + message.content + '\\n\\n' }}\n    {%- endif %}\n{%- endmacro %}\n{%- if not add_generation_prompt is defined %}\n{%- set add_generation_prompt = false %}\n{%- endif %}\n{%- for message in messages %}\n    {%- if message['role'] == 'user' %}\n        {{- __render_user_message(message) }}\n    {%- endif %}\n    {%- if message.role == 'assistant' and not loop.last %}\n        {{- __render_assistant_message(message) }}\n    {%- endif %}\n    {%- if message.role == 'tool' %}\n        {{- __render_tool_message(message) }}\n    {%- endif %}\n    {%- if loop.last %}\n        {{- ' Ассистент:[SEP]' }}\n    {%- endif %}\n{%- endfor %}\n",
-            /* .expected_output= */ "<s> Пользователь: Hello\n\n Ассистент: Hi there\n\n Пользователь: Who are you\n\n Ассистент:    I am an assistant   \n\n Пользователь: Another question\n\n Ассистент:[SEP]",
+            /* .expected_output= */ " Пользователь: Hello\n\n Ассистент: Hi there\n\n Пользователь: Who are you\n\n Ассистент:    I am an assistant   \n\n Пользователь: Another question\n\n Ассистент:[SEP]",
             /* .expected_output_jinja= */ "<s> Пользователь: You are a helpful assistant\nHello\n\n Ассистент: Hi there\n\n Пользователь: Who are you\n\n Ассистент:    I am an assistant   \n\n Пользователь: Another question\n\n Ассистент:[SEP]",
-            /* .bos_token= */ "",
+            /* .bos_token= */ "<s>",
             /* .eos_token= */ "",
         },
         {