chat : only remove double bos/eos if added (#15086)

* only remove double bos/eos if added

* fix tests

Author: CISC

common/chat.cpp

@@ -126,6 +126,8 @@ std::vector<common_chat_msg_diff> common_chat_msg_diff::compute_diffs(const comm
 typedef minja::chat_template common_chat_template;
 
 struct common_chat_templates {
+    bool add_bos;
+    bool add_eos;
     bool has_explicit_template; // Model had builtin template or template overridde was specified.
     std::unique_ptr<common_chat_template> template_default; // always set (defaults to chatml)
     std::unique_ptr<common_chat_template> template_tool_use;
@@ -143,6 +145,8 @@ struct templates_params {
     bool enable_thinking = true;
     std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
     json extra_context;
+    bool add_bos;
+    bool add_eos;
 };
 
 common_chat_tool_choice common_chat_tool_choice_parse_oaicompat(const std::string & tool_choice) {
@@ -445,6 +449,8 @@ std::string common_chat_format_single(
 
     common_chat_templates_inputs inputs;
     inputs.use_jinja = use_jinja;
+    inputs.add_bos = tmpls->add_bos;
+    inputs.add_eos = tmpls->add_eos;
 
     std::string fmt_past_msg;
     if (!past_msg.empty()) {
@@ -469,6 +475,8 @@ std::string common_chat_format_single(
 std::string common_chat_format_example(const struct common_chat_templates * tmpls, bool use_jinja) {
     common_chat_templates_inputs inputs;
     inputs.use_jinja = use_jinja;
+    inputs.add_bos = tmpls->add_bos;
+    inputs.add_eos = tmpls->add_eos;
     auto add_simple_msg = [&](auto role, auto content) {
         common_chat_msg msg;
         msg.role = role;
@@ -546,6 +554,8 @@ common_chat_templates_ptr common_chat_templates_init(
     }
     std::string token_bos = bos_token_override;
     std::string token_eos = eos_token_override;
+    bool add_bos = false;
+    bool add_eos = false;
     if (model) {
         const auto * vocab = llama_model_get_vocab(model);
         const auto get_token = [&](llama_token token, const char * name, const char * jinja_variable_name) {
@@ -560,9 +570,13 @@ common_chat_templates_ptr common_chat_templates_init(
         };
         token_bos = get_token(llama_vocab_bos(vocab), "BOS", "bos_token");
         token_eos = get_token(llama_vocab_eos(vocab), "EOS", "eos_token");
+        add_bos = llama_vocab_get_add_bos(vocab);
+        add_eos = llama_vocab_get_add_eos(vocab);
     }
     common_chat_templates_ptr tmpls(new common_chat_templates());
     tmpls->has_explicit_template = has_explicit_template;
+    tmpls->add_bos = add_bos;
+    tmpls->add_eos = add_eos;
     try {
         tmpls->template_default = std::make_unique<minja::chat_template>(default_template_src, token_bos, token_eos);
     } catch (const std::exception & e) {
@@ -748,10 +762,10 @@ static std::string apply(
     // instead of using `chat_template_options.use_bos_token = false`, since these tokens
     // may be needed inside the template / between messages too.
     auto result = tmpl.apply(tmpl_inputs, tmpl_opts);
-    if (string_starts_with(result, tmpl.bos_token())) {
+    if (inputs.add_bos && string_starts_with(result, tmpl.bos_token())) {
         result = result.substr(tmpl.bos_token().size());
     }
-    if (string_ends_with(result, tmpl.eos_token())) {
+    if (inputs.add_eos && string_ends_with(result, tmpl.eos_token())) {
         result = result.substr(0, result.size() - tmpl.eos_token().size());
     }
     return result;
@@ -1731,6 +1745,8 @@ static common_chat_params common_chat_templates_apply_jinja(
     params.enable_thinking = inputs.enable_thinking;
     params.grammar = inputs.grammar;
     params.now = inputs.now;
+    params.add_bos = inputs.add_bos;
+    params.add_eos = inputs.add_eos;
 
     params.extra_context = json::object();
     for (auto el : inputs.chat_template_kwargs) {

common/chat.h

@@ -127,6 +127,8 @@ struct common_chat_templates_inputs {
     bool enable_thinking = true;
     std::chrono::system_clock::time_point now = std::chrono::system_clock::now();
     std::map<std::string, std::string> chat_template_kwargs;
+    bool add_bos = false;
+    bool add_eos = false;
 };
 
 struct common_chat_params {

tests/test-chat-template.cpp

@@ -61,7 +61,7 @@ int main(void) {
             /* .name= */ "mistralai/Mistral-7B-Instruct-v0.2 (NOTE: Old pre-v1 without a system prompt)",
             /* .template_str= */ "{{ bos_token }}{% for message in messages %}{% if (message['role'] == 'user') != (loop.index0 % 2 == 0) %}{{ raise_exception('Conversation roles must alternate user/assistant/user/assistant/...') }}{% endif %}{% if message['role'] == 'user' %}{{ '[INST] ' + message['content'] + ' [/INST]' }}{% elif message['role'] == 'assistant' %}{{ message['content'] + eos_token}}{% else %}{{ raise_exception('Only user and assistant roles are supported!') }}{% endif %}{% endfor %}",
             /* .expected_output= */ "[INST] You are a helpful assistant\nHello [/INST]Hi there</s>[INST] Who are you [/INST]   I am an assistant   </s>[INST] Another question [/INST]",
-            /* .expected_output_jinja= */ "",
+            /* .expected_output_jinja= */ "<s>[INST] You are a helpful assistant\nHello [/INST]Hi there</s>[INST] Who are you [/INST]   I am an assistant   </s>[INST] Another question [/INST]",
             /* .bos_token= */ "<s>",
             /* .eos_token= */ "</s>",
         },
@@ -85,7 +85,7 @@ int main(void) {
             /* .name= */ "mlabonne/AlphaMonarch-7B",
             /* .template_str= */ "{% for message in messages %}{{bos_token + message['role'] + '\\n' + message['content'] + eos_token + '\\n'}}{% endfor %}{% if add_generation_prompt %}{{ bos_token + 'assistant\\n' }}{% endif %}",
             /* .expected_output= */ "system\nYou are a helpful assistant</s>\n<s>user\nHello</s>\n<s>assistant\nHi there</s>\n<s>user\nWho are you</s>\n<s>assistant\n   I am an assistant   </s>\n<s>user\nAnother question</s>\n<s>assistant\n",
-            /* .expected_output_jinja= */ "",
+            /* .expected_output_jinja= */ "<s>system\nYou are a helpful assistant</s>\n<s>user\nHello</s>\n<s>assistant\nHi there</s>\n<s>user\nWho are you</s>\n<s>assistant\n   I am an assistant   </s>\n<s>user\nAnother question</s>\n<s>assistant\n",
             /* .bos_token= */ "<s>",
             /* .eos_token= */ "</s>",
         },
@@ -99,7 +99,7 @@ int main(void) {
             /* .name= */ "OrionStarAI/Orion-14B-Chat",
             /* .template_str= */ "{% for message in messages %}{% if loop.first %}{{ bos_token }}{% endif %}{% if message['role'] == 'user' %}{{ 'Human: ' + message['content'] + '\\n\\nAssistant: ' + eos_token }}{% elif message['role'] == 'assistant' %}{{ message['content'] + eos_token }}{% endif %}{% endfor %}",
             /* .expected_output= */       "Human: You are a helpful assistant\n\nHello\n\nAssistant: </s>Hi there</s>Human: Who are you\n\nAssistant: </s>   I am an assistant   </s>Human: Another question\n\nAssistant: </s>",
-            /* .expected_output_jinja= */ "Human: You are a helpful assistant\nHello\n\nAssistant: </s>Hi there</s>Human: Who are you\n\nAssistant: </s>   I am an assistant   </s>Human: Another question\n\nAssistant: ",
+            /* .expected_output_jinja= */ "Human: You are a helpful assistant\nHello\n\nAssistant: </s>Hi there</s>Human: Who are you\n\nAssistant: </s>   I am an assistant   </s>Human: Another question\n\nAssistant: </s>",
             /* .bos_token= */ "",
             /* .eos_token= */ "</s>",
         },