refactor: smart `function_calling` config value (#677)

src/config/mod.rs

@@ -162,7 +162,7 @@ impl Default for Config {
             repl_prelude: None,
             agent_prelude: None,
 
-            function_calling: false,
+            function_calling: true,
             dangerously_functions_filter: None,
             agents: vec![],
 
@@ -222,9 +222,9 @@ impl Config {
             config.set_wrap(&wrap)?;
         }
 
-        config.functions = Functions::init(&Self::functions_file()?)?;
-
         config.working_mode = working_mode;
+
+        config.load_functions()?;
         config.load_roles()?;
 
         config.setup_model()?;
@@ -531,6 +531,11 @@ impl Config {
             }
             "function_calling" => {
                 let value = value.parse().with_context(|| "Invalid value")?;
+                if value && self.functions.is_empty() {
+                    bail!(
+                        "Cannot enable function_calling because there are no functions installed."
+                    )
+                }
                 self.function_calling = value;
             }
             "compress_threshold" => {
@@ -949,7 +954,7 @@ impl Config {
         abort_signal: AbortSignal,
     ) -> Result<()> {
         if !config.read().function_calling {
-            bail!("Before using the agent, please configure function calling first.");
+            bail!("Please enable function calling before using the agent.");
         }
         if config.read().agent.is_some() {
             bail!("Already in a agent, please run '.exit agent' first to exit the current agent.");
@@ -1385,6 +1390,14 @@ impl Config {
         Ok(config)
     }
 
+    fn load_functions(&mut self) -> Result<()> {
+        self.functions = Functions::init(&Self::functions_file()?)?;
+        if self.functions.is_empty() {
+            self.function_calling = false;
+        }
+        Ok(())
+    }
+
     fn load_roles(&mut self) -> Result<()> {
         let path = Self::roles_file()?;
         self.roles = if !path.exists() {

src/function.rs

@@ -62,7 +62,7 @@ impl Functions {
         let declarations: Vec<FunctionDeclaration> = if declarations_path.exists() {
             let ctx = || {
                 format!(
-                    "Failed to load function declarations at {}",
+                    "Failed to load functions at {}",
                     declarations_path.display()
                 )
             };