minja: fix string subscripts, add string pipe to support Mistral-Nemo template

common/minja.hpp

@@ -236,7 +236,7 @@ public:
       if (it == object_->end()) return Value();
       return it->second;
     }
-    throw std::runtime_error("Value is not an array or object: " + dump());
+    return Value();
   }
   void set(const Value& key, const Value& value) {
     if (!object_) throw std::runtime_error("Value is not an object: " + dump());
@@ -1092,15 +1092,24 @@ public:
         if (!index) throw std::runtime_error("SubscriptExpr.index is null");
         auto target_value = base->evaluate(context);
         if (auto slice = dynamic_cast<SliceExpr*>(index.get())) {
-          if (!target_value.is_array()) throw std::runtime_error("Subscripting non-array");
+          auto start = slice->start ? slice->start->evaluate(context).get<int64_t>() : 0;
-
+          auto end = slice->end ? slice->end->evaluate(context).get<int64_t>() : (int64_t) target_value.size();
-          auto start = slice->start ? slice->start->evaluate(context).get<size_t>() : 0;
+          if (target_value.is_string()) {
-          auto end = slice->end ? slice->end->evaluate(context).get<size_t>() : target_value.size();
+            std::string s = target_value.get<std::string>();
-          auto result = Value::array();
+            if (start < 0) start = s.size() + start;
-          for (auto i = start; i < end; ++i) {
+            if (end < 0) end = s.size() + end;
-            result.push_back(target_value.at(i));
+            return s.substr(start, end - start);
+          } else if (target_value.is_array()) {
+            if (start < 0) start = target_value.size() + start;
+            if (end < 0) end = target_value.size() + end;
+            auto result = Value::array();
+            for (auto i = start; i < end; ++i) {
+              result.push_back(target_value.at(i));
+            }
+            return result;
+          } else {
+            throw std::runtime_error(target_value.is_null() ? "Cannot subscript null" : "Subscripting only supported on arrays and strings");
           }
-          return result;
         } else {
           auto index_value = index->evaluate(context);
           if (target_value.is_null()) {
@@ -1247,6 +1256,9 @@ public:
         if (!object) throw std::runtime_error("MethodCallExpr.object is null");
         if (!method) throw std::runtime_error("MethodCallExpr.method is null");
         auto obj = object->evaluate(context);
+        if (obj.is_null()) {
+          throw std::runtime_error("Trying to call method '" + method->get_name() + "' on null");
+        }
         if (obj.is_array()) {
           if (method->get_name() == "append") {
               args.expectArgs("append method", {1, 1}, {0, 0});
@@ -2403,6 +2415,10 @@ inline std::shared_ptr<Context> Context::builtins() {
   globals.set("safe", simple_function("safe", { "value" }, [](const std::shared_ptr<Context> &, Value & args) -> Value {
       return args.at("value");
   }));
+  globals.set("string", simple_function("string", { "value" }, [](const std::shared_ptr<Context> &, Value & args) -> Value {
+      auto & items = args.at("value");
+      return items.to_str();
+  }));
   globals.set("list", simple_function("list", { "items" }, [](const std::shared_ptr<Context> &, Value & args) -> Value {
       auto & items = args.at("items");
       if (!items.is_array()) throw std::runtime_error("object is not iterable");

scripts/update_jinja_goldens.py

@@ -60,6 +60,7 @@ model_ids = [
     # Gated models:
     "meta-llama/Llama-3.2-3B-Instruct",
     "meta-llama/Meta-Llama-3.1-8B-Instruct",
+    "mistralai/Mistral-Nemo-Instruct-2407",
     "google/gemma-7b-it",
     "google/gemma-2-2b-it",
     "mistralai/Mistral-7B-Instruct-v0.2",

tests/chat/goldens/mistralai-Mistral-Nemo-Instruct-2407-simple.txt

@@ -0,0 +1 @@
+<|startoftext|>[INST]What's your favourite LLM framework?[/INST]llama.cpp!<|endoftext|>

tests/chat/goldens/mistralai-Mistral-Nemo-Instruct-2407-system.txt

@@ -0,0 +1 @@
+<|startoftext|>[INST]What's your favourite LLM framework?[/INST]llama.cpp!<|endoftext|>

tests/chat/goldens/mistralai-Mistral-Nemo-Instruct-2407-tool_use.txt

@@ -0,0 +1 @@
+<|startoftext|>[INST]Print a hello world message with python.[/INST][TOOL_CALLS][{"arguments": "{\"code\": \"print('Hello, World!')\"}", "name": "ipython", "id": "call_1___"}]<|endoftext|>[TOOL_RESULTS]{"content": {"stdout": "Hello, World!"}, "call_id": "call_1___"}[/TOOL_RESULTS]Anything else?<|endoftext|>[INST]Test a tautology.[/INST][TOOL_CALLS][{"arguments": "{\"condition\":true}", "name": "test", "id": "call_2___"}]<|endoftext|>[TOOL_RESULTS]{"content": true, "call_id": "call_2___"}[/TOOL_RESULTS]Truth is definitely true.<|endoftext|>[AVAILABLE_TOOLS][{"type": "function", "function": {"name": "ipython", "description": "Runs code in an ipython interpreter and returns the result of the execution after 60 seconds.", "parameters": {"type": "object", "properties": {"code": {"type": "string", "description": "The code to run in the ipython interpreter."}}, "required": ["code"]}}}, {"type": "function", "function": {"name": "brave_search", "description": "Executes a web search with Brave.", "parameters": {"type": "object", "properties": {"query": {"type": "string", "description": "The query to search for."}}, "required": ["query"]}}}, {"type": "function", "function": {"name": "wolfram_alpha", "description": "Executes a query with Wolfram Alpha.", "parameters": {"type": "object", "properties": {"query": {"type": "string", "description": "The query to execute."}}, "required": ["query"]}}}, {"type": "function", "function": {"name": "test", "description": "Runs a test.", "parameters": {"type": "object", "properties": {"condition": {"type": "boolean", "description": "The condition to test."}}, "required": ["condition"]}}}][/AVAILABLE_TOOLS][INST]Check it on the web.[/INST][TOOL_CALLS][{"arguments": "{\"query\": \"what is truth anyway am I right?\"}", "name": "brave_search", "id": "call_3___"}]<|endoftext|>[TOOL_RESULTS]{"content": {"title":"Truth: don't ask the web, ask an LLM instead!","url":"https://en.wikipedia.org/wiki/Truth"}, "call_id": "call_3___"}[/TOOL_RESULTS]I don't need the web to answer you but I did check, as you asked. What now?<|endoftext|>

tests/chat/templates/mistralai-Mistral-Nemo-Instruct-2407.jinja

@@ -0,0 +1,87 @@
+{%- if messages[0]["role"] == "system" %}
+    {%- set system_message = messages[0]["content"] %}
+    {%- set loop_messages = messages[1:] %}
+{%- else %}
+    {%- set loop_messages = messages %}
+{%- endif %}
+{%- if not tools is defined %}
+    {%- set tools = none %}
+{%- endif %}
+{%- set user_messages = loop_messages | selectattr("role", "equalto", "user") | list %}
+
+{#- This block checks for alternating user/assistant messages, skipping tool calling messages #}
+{%- set ns = namespace() %}
+{%- set ns.index = 0 %}
+{%- for message in loop_messages %}
+    {%- if not (message.role == "tool" or message.role == "tool_results" or (message.tool_calls is defined and message.tool_calls is not none)) %}
+        {%- if (message["role"] == "user") != (ns.index % 2 == 0) %}
+            {{- raise_exception("After the optional system message, conversation roles must alternate user/assistant/user/assistant/...") }}
+        {%- endif %}
+        {%- set ns.index = ns.index + 1 %}
+    {%- endif %}
+{%- endfor %}
+
+{{- bos_token }}
+{%- for message in loop_messages %}
+    {%- if message["role"] == "user" %}
+        {%- if tools is not none and (message == user_messages[-1]) %}
+            {{- "[AVAILABLE_TOOLS][" }}
+            {%- for tool in tools %}
+                {%- set tool = tool.function %}
+                {{- '{"type": "function", "function": {' }}
+                {%- for key, val in tool.items() if key != "return" %}
+                    {%- if val is string %}
+                        {{- '"' + key + '": "' + val + '"' }}
+                    {%- else %}
+                        {{- '"' + key + '": ' + val|tojson }}
+                    {%- endif %}
+                    {%- if not loop.last %}
+                        {{- ", " }}
+                    {%- endif %}
+                {%- endfor %}
+                {{- "}}" }}
+                {%- if not loop.last %}
+                    {{- ", " }}
+                {%- else %}
+                    {{- "]" }}
+                {%- endif %}
+            {%- endfor %}
+            {{- "[/AVAILABLE_TOOLS]" }}
+            {%- endif %}
+        {%- if loop.last and system_message is defined %}
+            {{- "[INST]" + system_message + "\n\n" + message["content"] + "[/INST]" }}
+        {%- else %}
+            {{- "[INST]" + message["content"] + "[/INST]" }}
+        {%- endif %}
+    {%- elif (message.tool_calls is defined and message.tool_calls is not none) %}
+        {{- "[TOOL_CALLS][" }}
+        {%- for tool_call in message.tool_calls %}
+            {%- set out = tool_call.function|tojson %}
+            {{- out[:-1] }}
+            {%- if not tool_call.id is defined or tool_call.id|length != 9 %}
+                {{- raise_exception("Tool call IDs should be alphanumeric strings with length 9!") }}
+            {%- endif %}
+            {{- ', "id": "' + tool_call.id + '"}' }}
+            {%- if not loop.last %}
+                {{- ", " }}
+            {%- else %}
+                {{- "]" + eos_token }}
+            {%- endif %}
+        {%- endfor %}
+    {%- elif message["role"] == "assistant" %}
+        {{- message["content"] + eos_token}}
+    {%- elif message["role"] == "tool_results" or message["role"] == "tool" %}
+        {%- if message.content is defined and message.content.content is defined %}
+            {%- set content = message.content.content %}
+        {%- else %}
+            {%- set content = message.content %}
+        {%- endif %}
+        {{- '[TOOL_RESULTS]{"content": ' + content|string + ", " }}
+        {%- if not message.tool_call_id is defined or message.tool_call_id|length != 9 %}
+            {{- raise_exception("Tool call IDs should be alphanumeric strings with length 9!") }}
+        {%- endif %}
+        {{- '"call_id": "' + message.tool_call_id + '"}[/TOOL_RESULTS]' }}
+    {%- else %}
+        {{- raise_exception("Only user and assistant roles are supported, with the exception of an initial optional system message!") }}
+    {%- endif %}
+{%- endfor %}

tests/test-minja.cpp

@@ -141,6 +141,9 @@ int main() {
         lstrip_trim_blocks,
         "        1"
     );
+    test_render(R"({{ "abcd"[1:-1] }})", {}, {}, "bc");
+    test_render(R"({{ [0, 1, 2, 3][1:-1] }})", {}, {}, "[1, 2]");
+    test_render(R"({{ "123456789" | length }})", {}, {}, "9");
     test_render(R"(  {{- 'a' -}}{{ '  ' }}{{- 'b' -}}  )", {}, {}, "a  b");
     test_render(R"(    {%- if True %}{%- endif %}{{ '        ' }}{%- for x in [] %}foo{% endfor %}end)", {}, {}, "        end");
     test_render(R"({% set ns = namespace(is_first=false, nottool=false, and_or=true, delme='') %}{{ ns.is_first }})", {}, {}, "False");