assistant_tools: Reduce allocations (#30776)

Another batch of allocation savings. Noteworthy ones are
`find_path_tool.rs` where one clone of *all* found matches was saved and
`web_tool_search.rs` where the tooltip no longer clones the entire url
on every hover.

I'd also like to propose using `std::borrow::Cow` a lot more around the
codebase instead of Strings. There are hundreds if not 1000+ clones that
can be saved pretty regularly simply by switching to Cow. ´Cow´'s are
likely not used because they aren't compatible with futures and because
it could cause lifetime bloat. However if we use `Cow<'static, str>`
(static lifetime) for when we need to pass them into futures, we could
save a TON of allocations for `&'static str`. Additionally I often see
structs being created using `String`'s just to be deserialized
afterwards, which only requires a reference.

Release Notes:

- N/A

crates/assistant_tools/src/fetch_tool.rs

@@ -1,6 +1,6 @@
-use std::cell::RefCell;
 use std::rc::Rc;
 use std::sync::Arc;
+use std::{borrow::Cow, cell::RefCell};
 
 use crate::schema::json_schema_for;
 use anyhow::{Context as _, Result, anyhow, bail};
@@ -39,10 +39,11 @@ impl FetchTool {
     }
 
     async fn build_message(http_client: Arc<HttpClientWithUrl>, url: &str) -> Result<String> {
-        let mut url = url.to_owned();
-        if !url.starts_with("https://") && !url.starts_with("http://") {
-            url = format!("https://{url}");
-        }
+        let url = if !url.starts_with("https://") && !url.starts_with("http://") {
+            Cow::Owned(format!("https://{url}"))
+        } else {
+            Cow::Borrowed(url)
+        };
 
         let mut response = http_client.get(&url, AsyncBody::default(), true).await?;
 
@@ -156,8 +157,7 @@ impl Tool for FetchTool {
 
         let text = cx.background_spawn({
             let http_client = self.http_client.clone();
-            let url = input.url.clone();
-            async move { Self::build_message(http_client, &url).await }
+            async move { Self::build_message(http_client, &input.url).await }
         });
 
         cx.foreground_executor()

crates/assistant_tools/src/find_path_tool.rs

@@ -119,14 +119,16 @@ impl Tool for FindPathTool {
                     )
                     .unwrap();
                 }
-                let output = FindPathToolOutput {
-                    glob,
-                    paths: matches.clone(),
-                };
 
-                for mat in matches.into_iter().skip(offset).take(RESULTS_PER_PAGE) {
+                for mat in matches.iter().skip(offset).take(RESULTS_PER_PAGE) {
                     write!(&mut message, "\n{}", mat.display()).unwrap();
                 }
+
+                let output = FindPathToolOutput {
+                    glob,
+                    paths: matches,
+                };
+
                 Ok(ToolResultOutput {
                     content: ToolResultContent::Text(message),
                     output: Some(serde_json::to_value(output)?),
@@ -235,8 +237,6 @@ impl ToolCard for FindPathToolCard {
             format!("{} matches", self.paths.len()).into()
         };
 
-        let glob_label = self.glob.to_string();
-
         let content = if !self.paths.is_empty() && self.expanded {
             Some(
                 v_flex()
@@ -310,7 +310,7 @@ impl ToolCard for FindPathToolCard {
             .gap_1()
             .child(
                 ToolCallCardHeader::new(IconName::SearchCode, matches_label)
-                    .with_code_path(glob_label)
+                    .with_code_path(&self.glob)
                     .disclosure_slot(
                         Disclosure::new("path-search-disclosure", self.expanded)
                             .opened_icon(IconName::ChevronUp)

crates/assistant_tools/src/terminal_tool.rs

@@ -182,9 +182,8 @@ impl Tool for TerminalTool {
                 let mut child = pair.slave.spawn_command(cmd)?;
                 let mut reader = pair.master.try_clone_reader()?;
                 drop(pair);
-                let mut content = Vec::new();
-                reader.read_to_end(&mut content)?;
-                let mut content = String::from_utf8(content)?;
+                let mut content = String::new();
+                reader.read_to_string(&mut content)?;
                 // Massage the pty output a bit to try to match what the terminal codepath gives us
                 LineEnding::normalize(&mut content);
                 content = content

crates/assistant_tools/src/web_search_tool.rs

@@ -166,7 +166,7 @@ impl ToolCard for WebSearchToolCard {
                     .gap_1()
                     .children(response.results.iter().enumerate().map(|(index, result)| {
                         let title = result.title.clone();
-                        let url = result.url.clone();
+                        let url = SharedString::from(result.url.clone());
 
                         Button::new(("result", index), title)
                             .label_size(LabelSize::Small)