Fix /completions endpoint by separating completion and chat completion parsing

- Add new oaicompat_completion_params_parse() for simple completions
- Rename existing function to oaicompat_chat_completion_params_parse()
- Update /completions endpoint to use simple parser (no chat templates)
- Update /chat/completions endpoint to use chat parser (with tools support)
- Fixes compatibility issue introduced in tool calling PR ikawrakow#677

Incorporates fixes from upstream PR ikawrakow#684

Author: RodriMora

examples/server/server.cpp

@@ -3602,9 +3602,7 @@ int main(int argc, char ** argv) {
         }
 
         res.set_header("Access-Control-Allow-Origin", req.get_header_value("Origin"));
-        auto body = json::parse(req.body);
-        const auto& chat_template = body.contains("tools") && ctx_server.chat_templates.template_tool_use ? *ctx_server.chat_templates.template_tool_use : *ctx_server.chat_templates.template_default;
-        json data = oaicompat_completion_params_parse(ctx_server.model, body, chat_template, ctx_server.params.use_jinja);
+        json data = oaicompat_completion_params_parse(json::parse(req.body));
 
         const int id_task = ctx_server.queue_tasks.get_new_id();
 
@@ -3707,7 +3705,7 @@ int main(int argc, char ** argv) {
 
         auto body = json::parse(req.body);
         const auto& chat_template = body.contains("tools") && ctx_server.chat_templates.template_tool_use ? *ctx_server.chat_templates.template_tool_use : *ctx_server.chat_templates.template_default;
-        json data = oaicompat_completion_params_parse(ctx_server.model,body, chat_template, params.use_jinja);
+        json data = oaicompat_chat_completion_params_parse(ctx_server.model,body, chat_template, params.use_jinja);
 
 
         const int id_task = ctx_server.queue_tasks.get_new_id();

examples/server/utils.hpp

@@ -424,7 +424,47 @@ static tool_choice_type tool_choice_parse_oaicompat(const std::string & tool_cho
 // OAI utils
 //
 
-static json oaicompat_completion_params_parse(
+static json oaicompat_completion_params_parse(const json& body) {
+    json llama_params;
+
+    if (!body.contains("prompt")) {
+        throw std::runtime_error("\"prompt\" is required");
+    }
+
+    // Handle "stop" field
+    if (body.contains("stop") && body.at("stop").is_string()) {
+        llama_params["stop"] = json::array({ body.at("stop").get<std::string>() });
+    }
+    else {
+        llama_params["stop"] = json_value(body, "stop", json::array());
+    }
+
+    // Handle "n" field
+    int n_choices = json_value(body, "n", 1);
+    if (n_choices != 1) {
+        throw std::runtime_error("Only one completion choice is allowed");
+    }
+
+    // Params supported by OAI but unsupported by llama.cpp
+    static const std::vector<std::string> unsupported_params{ "best_of", "echo", "suffix" };
+    for (const auto& param : unsupported_params) {
+        if (body.contains(param)) {
+            throw std::runtime_error("Unsupported param: " + param);
+        }
+    }
+
+    // Copy remaining properties to llama_params
+    for (const auto& item : body.items()) {
+        // Exception: if "n_predict" is present, we overwrite the value specified earlier by "max_tokens"
+        if (!llama_params.contains(item.key()) || item.key() == "n_predict") {
+            llama_params[item.key()] = item.value();
+        }
+    }
+
+    return llama_params;
+}
+
+static json oaicompat_chat_completion_params_parse(
     const struct llama_model * model,
     const json & body, /* openai api json semantics */
     const common_chat_template& tmpl,