Add strftime_now callable function for minijinja chat templates

router/Cargo.toml

@@ -64,6 +64,7 @@ uuid = { version = "1.9.1", default-features = false, features = [
 csv = "1.3.0"
 ureq = "=2.9"
 pyo3 = { workspace = true }
+chrono = "0.4.39"
 
 
 [build-dependencies]

router/src/infer/chat_template.rs

@@ -1,5 +1,6 @@
 use crate::infer::InferError;
 use crate::{ChatTemplateInputs, Message, MessageChunk, TextMessage, TokenizerConfigToken, Tool};
+use chrono::Local;
 use minijinja::{Environment, ErrorKind, Template};
 use minijinja_contrib::pycompat;
 
@@ -8,6 +9,11 @@ pub(crate) fn raise_exception(err_text: String) -> Result<String, minijinja::Err
     Err(minijinja::Error::new(ErrorKind::SyntaxError, err_text))
 }
 
+/// Get the current date in a specific format (custom function), similar to `datetime.now().strftime()` in Python
+pub(crate) fn strftime_now(format_str: String) -> Result<String, minijinja::Error> {
+    Ok(Local::now().format(&format_str).to_string())
+}
+
 #[derive(Clone)]
 pub(crate) struct ChatTemplate {
     template: Template<'static, 'static>,
@@ -27,6 +33,7 @@ impl ChatTemplate {
         env.set_unknown_method_callback(pycompat::unknown_method_callback);
         let template_str = template.into_boxed_str();
         env.add_function("raise_exception", raise_exception);
+        env.add_function("strftime_now", strftime_now);
         tracing::debug!("Loading template: {}", template_str);
 
         // leaking env and template_str as read-only, static resources for performance.
@@ -109,11 +116,12 @@ impl ChatTemplate {
 // tests
 #[cfg(test)]
 mod tests {
-    use crate::infer::chat_template::raise_exception;
+    use crate::infer::chat_template::{raise_exception, strftime_now};
     use crate::infer::ChatTemplate;
     use crate::{
         ChatTemplateInputs, Message, MessageContent, TextMessage, TokenizerConfigToken, Tool,
     };
+    use chrono::Local;
     use minijinja::Environment;
 
     #[test]
@@ -182,6 +190,7 @@ mod tests {
     fn test_chat_template_invalid_with_raise() {
         let mut env = Environment::new();
         env.add_function("raise_exception", raise_exception);
+        env.add_function("strftime_now", strftime_now);
 
         let source = r#"
         {{ bos_token }}
@@ -253,6 +262,7 @@ mod tests {
     fn test_chat_template_valid_with_raise() {
         let mut env = Environment::new();
         env.add_function("raise_exception", raise_exception);
+        env.add_function("strftime_now", strftime_now);
 
         let source = r#"
         {{ bos_token }}
@@ -307,10 +317,79 @@ mod tests {
         assert_eq!(result, "[BOS][INST] Hi! [/INST]Hello how can I help?[EOS][INST] What is Deep Learning? [/INST]magic![EOS]");
     }
 
+    #[test]
+    fn test_chat_template_valid_with_strftime_now() {
+        let mut env = Environment::new();
+        env.add_function("raise_exception", raise_exception);
+        env.add_function("strftime_now", strftime_now);
+
+        let source = r#"
+        {% set today = strftime_now("%Y-%m-%d") %}
+        {% set default_system_message = "The current date is " + today + "." %}
+        {{ bos_token }}
+        {% if messages[0]['role'] == 'system' %}
+            { set system_message = messages[0]['content'] %}
+            {%- set loop_messages = messages[1:] %}
+        {% else %}
+            {%- set system_message = default_system_message %}
+            {%- set loop_messages = messages %}
+        {% endif %}
+        {{ '[SYSTEM_PROMPT]' + system_message + '[/SYSTEM_PROMPT]' }}
+        {% for message in loop_messages %}
+            {% 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 %}
+        "#;
+
+        // trim all the whitespace
+        let source = source
+            .lines()
+            .map(|line| line.trim())
+            .collect::<Vec<&str>>()
+            .join("");
+
+        let tmpl = env.template_from_str(&source);
+
+        let chat_template_inputs = ChatTemplateInputs {
+            messages: vec![
+                TextMessage {
+                    role: "user".to_string(),
+                    content: "Hi!".to_string(),
+                },
+                TextMessage {
+                    role: "assistant".to_string(),
+                    content: "Hello how can I help?".to_string(),
+                },
+                TextMessage {
+                    role: "user".to_string(),
+                    content: "What is Deep Learning?".to_string(),
+                },
+                TextMessage {
+                    role: "assistant".to_string(),
+                    content: "magic!".to_string(),
+                },
+            ],
+            bos_token: Some("[BOS]"),
+            eos_token: Some("[EOS]"),
+            add_generation_prompt: true,
+            ..Default::default()
+        };
+
+        let current_date = Local::now().format("%Y-%m-%d").to_string();
+        let result = tmpl.unwrap().render(chat_template_inputs).unwrap();
+        assert_eq!(result, format!("[BOS][SYSTEM_PROMPT]The current date is {}.[/SYSTEM_PROMPT][INST]Hi![/INST]Hello how can I help?[EOS][INST]What is Deep Learning?[/INST]magic![EOS]", current_date));
+    }
+
     #[test]
     fn test_chat_template_valid_with_add_generation_prompt() {
         let mut env = Environment::new();
         env.add_function("raise_exception", raise_exception);
+        env.add_function("strftime_now", strftime_now);
 
         let source = r#"
         {% for message in messages %}
@@ -502,6 +581,7 @@ mod tests {
         {
             let mut env = Environment::new();
             env.add_function("raise_exception", raise_exception);
+            env.add_function("strftime_now", strftime_now);
             let tmpl = env.template_from_str(chat_template);
             let result = tmpl.unwrap().render(input).unwrap();
             assert_eq!(result, target);
@@ -776,6 +856,7 @@ mod tests {
         {
             let mut env = Environment::new();
             env.add_function("raise_exception", raise_exception);
+            env.add_function("strftime_now", strftime_now);
             // trim all the whitespace
             let chat_template = chat_template
                 .lines()