⚡ Bolt: eliminate string cloning in sys_write_file and sys_read_file

.jules/bolt.md

@@ -70,3 +70,7 @@
 ## 2024-05-24 - Web Property Extraction Optimization
 **Learning:** Extracting properties from the `RuntimeValue` DSL property lists in `stdlib/src/web/renderer.rs` and `stdlib/src/web/db.rs` was inefficient because the code called `.iter().find()` to resolve `text`, `id`, and `name` attributes, which creates unnecessary iterator overhead and closure allocation.
 **Action:** Replace `.iter().find()` calls with a single-pass `for p in &dsl.properties` loop and `if` statements on the property names, stopping early when found, which significantly reduces execution overhead.
+
+## 2026-10-28 - Standard Library File Operations String Allocation Optimization
+**Learning:** Calling `try_into_string(&self)` on owned `RuntimeValue` arguments in standard library functions like `sys_write_file` and `sys_read_file` clones the string payload, causing redundant string allocations and memory copy overhead for file operations.
+**Action:** Provide and use an `into_string(self)` method on `RuntimeValue` when owned arguments are available in standard library callback handlers to extract strings directly without allocation.

runtime/runtime/src/value.rs

@@ -212,6 +212,13 @@ impl RuntimeValue {
         }
     }
 
+    pub fn into_string(self) -> Result<String, RuntimeError> {
+        match self {
+            Self::Str(s) => Ok(s),
+            other => Ok(other.to_string()),
+        }
+    }
+
     /// Verifies reference identity check (===).
     pub fn physical_eq(&self, other: &Self) -> bool {
         match (self, other) {

stdlib/src/sys.rs

@@ -25,7 +25,20 @@ fn sys_read_file(
     args: Vec<RuntimeValue>,
 ) -> Result<RuntimeValue, RuntimeError> {
     check_fs_capability(ctx)?;
-    let path = args[0].try_into_string()?;
+    let mut args_iter = args.into_iter();
+    let path = args_iter
+        .next()
+        .ok_or_else(|| {
+            RuntimeError::new(
+                RuntimeErrorKind::ArityMismatch {
+                    expected: 1,
+                    found: 0,
+                },
+                None,
+                None,
+            )
+        })?
+        .into_string()?;
     let content = std::fs::read_to_string(path).map_err(|e| {
         RuntimeError::new(
             RuntimeErrorKind::InvalidOperation(format!("IO error: {}", e)),
@@ -41,8 +54,33 @@ fn sys_write_file(
     args: Vec<RuntimeValue>,
 ) -> Result<RuntimeValue, RuntimeError> {
     check_fs_capability(ctx)?;
-    let path = args[0].try_into_string()?;
-    let content = args[1].try_into_string()?;
+    let mut args_iter = args.into_iter();
+    let path = args_iter
+        .next()
+        .ok_or_else(|| {
+            RuntimeError::new(
+                RuntimeErrorKind::ArityMismatch {
+                    expected: 2,
+                    found: 0,
+                },
+                None,
+                None,
+            )
+        })?
+        .into_string()?;
+    let content = args_iter
+        .next()
+        .ok_or_else(|| {
+            RuntimeError::new(
+                RuntimeErrorKind::ArityMismatch {
+                    expected: 2,
+                    found: 1,
+                },
+                None,
+                None,
+            )
+        })?
+        .into_string()?;
     std::fs::write(path, content).map_err(|e| {
         RuntimeError::new(
             RuntimeErrorKind::InvalidOperation(format!("IO error: {}", e)),
@@ -58,7 +96,20 @@ fn sys_exists(
     args: Vec<RuntimeValue>,
 ) -> Result<RuntimeValue, RuntimeError> {
     check_fs_capability(ctx)?;
-    let path = args[0].try_into_string()?;
+    let mut args_iter = args.into_iter();
+    let path = args_iter
+        .next()
+        .ok_or_else(|| {
+            RuntimeError::new(
+                RuntimeErrorKind::ArityMismatch {
+                    expected: 1,
+                    found: 0,
+                },
+                None,
+                None,
+            )
+        })?
+        .into_string()?;
     Ok(RuntimeValue::Bool(std::path::Path::new(&path).exists()))
 }