From fa0e7b09fa595794c87ccdd230c3e70e59cdce85 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Thu, 10 Sep 2026 05:14:45 +0000
Subject: [PATCH] =?UTF-8?q?=E2=9A=A1=20Bolt:=20avoid=20temporary=20allocat?=
 =?UTF-8?q?ions=20in=20format=20string=20generation?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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Replaced `push_str(&format!(...))` with `let _ = write!(buffer, ...)` via `std::fmt::Write` in string generation loops in stdlib `web.rs`, `xml.rs` and `yaml.rs`.
This prevents creating temporary strings that get immediately dropped and improves performance by writing directly to the target buffer.

Co-authored-by: Tcode-Motion <188012755+Tcode-Motion@users.noreply.github.com>
---
 .jules/bolt.md     |  3 +++
 stdlib/src/web.rs  | 40 +++++++++++++++++++---------------------
 stdlib/src/xml.rs  |  3 ++-
 stdlib/src/yaml.rs |  3 ++-
 4 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/.jules/bolt.md b/.jules/bolt.md
index 3311e44d..1d8c6be7 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -14,3 +14,6 @@
 ## 2024-05-24 - Avoid `push_str(&format!(...))` in loops
 **Learning:** Using `push_str(&format!(...))` inside loops creates unnecessary temporary String allocations because `format!` allocates a new `String` which is then appended and immediately dropped.
 **Action:** Use `std::fmt::Write` and the `write!` macro directly onto the target string buffer instead.
+## 2025-02-12 - String allocation optimization
+**Learning:** In heavily used loops, especially for rendering or stringifying tasks, `push_str(&format!(...))` allocates temporary strings unnecessarily. Replacing it with `write!` directly onto the mutable `String` buffer (using `std::fmt::Write`) skips the intermediate allocations and improves performance significantly.
+**Action:** Use `std::fmt::Write` and the `write!` macro instead of `push_str(&format!(...))` when generating strings in loops to prevent temporary allocations and improve performance.
diff --git a/stdlib/src/web.rs b/stdlib/src/web.rs
index 51c80510..500b9235 100644
--- a/stdlib/src/web.rs
+++ b/stdlib/src/web.rs
@@ -1,5 +1,6 @@
 use crate::{StdFunction, StdlibModule, StdlibRegistry};
 use std::collections::HashMap;
+use std::fmt::Write;
 use std::net::{IpAddr, SocketAddr, ToSocketAddrs};
 use std::rc::Rc;
 use std::sync::atomic::{AtomicBool, Ordering};
@@ -109,7 +110,7 @@ fn render_website(html: &mut String, dsl: &techscript_runtime::value::DslBlockVa
         match prop.name.as_str() {
             "title" => {
                 if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = &prop.value {
-                    html.push_str(&format!("<title>{}</title>", t));
+                    let _ = write!(html, "<title>{}</title>", t);
                 }
             }
             _ => {}
@@ -148,12 +149,12 @@ fn render_website(html: &mut String, dsl: &techscript_runtime::value::DslBlockVa
 fn render_page(html: &mut String, dsl: &techscript_runtime::value::DslBlockValue) {
     html.push_str("<div class=\"page\">");
     if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = dsl.args.first() {
-        html.push_str(&format!("<h1>{}</h1>", t));
+        let _ = write!(html, "<h1>{}</h1>", t);
     }
     for prop in &dsl.properties {
         if prop.name == "title" {
             if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = &prop.value {
-                html.push_str(&format!("<h2>{}</h2>", t));
+                let _ = write!(html, "<h2>{}</h2>", t);
             }
         }
     }
@@ -167,12 +168,12 @@ fn render_hero(html: &mut String, dsl: &techscript_runtime::value::DslBlockValue
         match prop.name.as_str() {
             "title" => {
                 if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = &prop.value {
-                    html.push_str(&format!("<h1>{}</h1>", t));
+                    let _ = write!(html, "<h1>{}</h1>", t);
                 }
             }
             "subtitle" => {
                 if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = &prop.value {
-                    html.push_str(&format!("<p class=\"subtitle\">{}</p>", t));
+                    let _ = write!(html, "<p class=\"subtitle\">{}</p>", t);
                 }
             }
             _ => {}
@@ -188,12 +189,12 @@ fn render_section(html: &mut String, dsl: &techscript_runtime::value::DslBlockVa
         match prop.name.as_str() {
             "title" => {
                 if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = &prop.value {
-                    html.push_str(&format!("<h2>{}</h2>", t));
+                    let _ = write!(html, "<h2>{}</h2>", t);
                 }
             }
             "id" => {
                 if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = &prop.value {
-                    html.push_str(&format!("<!-- id: {} -->", t));
+                    let _ = write!(html, "<!-- id: {} -->", t);
                 }
             }
             _ => {}
@@ -211,17 +212,17 @@ fn render_card(html: &mut String, dsl: &techscript_runtime::value::DslBlockValue
         match prop.name.as_str() {
             "title" => {
                 if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = &prop.value {
-                    html.push_str(&format!("<h3>{}</h3>", t));
+                    let _ = write!(html, "<h3>{}</h3>", t);
                 }
             }
             "text" => {
                 if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = &prop.value {
-                    html.push_str(&format!("<p>{}</p>", t));
+                    let _ = write!(html, "<p>{}</p>", t);
                 }
             }
             "image" => {
                 if let Some(techscript_runtime::value::RuntimeValue::Str(t)) = &prop.value {
-                    html.push_str(&format!("<img src=\"{}\" alt=\"card image\">", t));
+                    let _ = write!(html, "<img src=\"{}\" alt=\"card image\">", t);
                 }
             }
             _ => {}
@@ -259,7 +260,7 @@ fn dsl_to_html(val: &RuntimeValue) -> String {
                         .and_then(|p| p.value.as_ref())
                         .map(|v| v.to_string())
                         .unwrap_or_else(|| "Button".to_string());
-                    html.push_str(&format!("<button>{}</button>", label));
+                    let _ = write!(html, "<button>{}</button>", label);
                 }
                 "link" => {
                     let label = dsl
@@ -276,9 +277,9 @@ fn dsl_to_html(val: &RuntimeValue) -> String {
                         .and_then(|p| p.value.as_ref())
                         .map(|v| v.to_string());
                     if let Some(u) = url {
-                        html.push_str(&format!("<a href=\"{}\">{}</a>", u, label));
+                        let _ = write!(html, "<a href=\"{}\">{}</a>", u, label);
                     } else {
-                        html.push_str(&format!("<a href=\"#\">{}</a>", label));
+                        let _ = write!(html, "<a href=\"#\">{}</a>", label);
                     }
                 }
                 "nav" => {
@@ -291,7 +292,7 @@ fn dsl_to_html(val: &RuntimeValue) -> String {
                     for prop in &dsl.properties {
                         if prop.name == "title" {
                             if let Some(RuntimeValue::Str(t)) = &prop.value {
-                                html.push_str(&format!("<h1>{}</h1>", t));
+                                let _ = write!(html, "<h1>{}</h1>", t);
                             }
                         }
                     }
@@ -303,7 +304,7 @@ fn dsl_to_html(val: &RuntimeValue) -> String {
                     for prop in &dsl.properties {
                         if prop.name == "text" {
                             if let Some(RuntimeValue::Str(t)) = &prop.value {
-                                html.push_str(&format!("<p>{}</p>", t));
+                                let _ = write!(html, "<p>{}</p>", t);
                             }
                         }
                     }
@@ -318,7 +319,7 @@ fn dsl_to_html(val: &RuntimeValue) -> String {
                         .and_then(|p| p.value.as_ref())
                         .map(|v| v.to_string());
                     if let Some(p) = placeholder {
-                        html.push_str(&format!("<input placeholder=\"{}\">", p));
+                        let _ = write!(html, "<input placeholder=\"{}\">", p);
                     } else {
                         html.push_str("<input>");
                     }
@@ -346,13 +347,10 @@ fn dsl_to_html(val: &RuntimeValue) -> String {
                         .and_then(|p| p.value.as_ref())
                         .map(|v| v.to_string())
                         .unwrap_or_else(|| "Get Started".to_string());
-                    html.push_str(&format!(
-                        "<a class=\"start-button\" href=\"#\">{}</a>",
-                        label
-                    ));
+                    let _ = write!(html, "<a class=\"start-button\" href=\"#\">{}</a>", label);
                 }
                 _ => {
-                    html.push_str(&format!("<!-- unknown DSL block: {} -->", dsl.kind));
+                    let _ = write!(html, "<!-- unknown DSL block: {} -->", dsl.kind);
                 }
             }
             html
diff --git a/stdlib/src/xml.rs b/stdlib/src/xml.rs
index c3a3920a..7ea890c4 100644
--- a/stdlib/src/xml.rs
+++ b/stdlib/src/xml.rs
@@ -2,6 +2,7 @@ use crate::{StdFunction, StdlibModule, StdlibRegistry};
 use indexmap::IndexMap;
 use std::cell::RefCell;
 use std::collections::HashMap;
+use std::fmt::Write;
 use std::rc::Rc;
 use techscript_runtime::{error::RuntimeError, value::RuntimeValue};
 
@@ -44,7 +45,7 @@ impl StdlibRegistry {
                     if let RuntimeValue::Map { entries, .. } = &args[0] {
                         for (k, v) in entries.borrow().iter() {
                             let val_str = v.try_into_string().unwrap_or_default();
-                            result.push_str(&format!("<{}>{}</{}>", k, val_str, k));
+                            let _ = write!(result, "<{}>{}</{}>", k, val_str, k);
                         }
                     }
                     Ok(RuntimeValue::Str(result))
diff --git a/stdlib/src/yaml.rs b/stdlib/src/yaml.rs
index 92d9c527..84565181 100644
--- a/stdlib/src/yaml.rs
+++ b/stdlib/src/yaml.rs
@@ -2,6 +2,7 @@ use crate::{StdFunction, StdlibModule, StdlibRegistry};
 use indexmap::IndexMap;
 use std::cell::RefCell;
 use std::collections::HashMap;
+use std::fmt::Write;
 use std::rc::Rc;
 use techscript_runtime::{error::RuntimeError, value::RuntimeValue};
 
@@ -47,7 +48,7 @@ impl StdlibRegistry {
                     if let RuntimeValue::Map { entries, .. } = &args[0] {
                         for (k, v) in entries.borrow().iter() {
                             let val_str = v.try_into_string().unwrap_or_default();
-                            result.push_str(&format!("{}: {}\n", k, val_str));
+                            let _ = write!(result, "{}: {}\n", k, val_str);
                         }
                     }
                     Ok(RuntimeValue::Str(result))