perf(formatter_css,formatter_graphql,formatter_yaml,formatter_json): Pre alloc IR buffers (#25234)

As like `oxc_formatter`(js).

crates/oxc_formatter/src/formatter/mod.rs

@@ -45,8 +45,7 @@ pub fn format<'ast>(
 ) -> Formatted<'ast, JsFormatContext<'ast>> {
     // Pre-allocate buffer at 40% of source length (source_len * 2 / 5).
     // Analysis of 4,891 VSCode files shows FormatElement buffer length is typically 19% of source (median),
-    // with 95th percentile at 30-38% across all file sizes. This 0.4x multiplier avoids
-    // reallocation for 95%+ of files.
+    // with 95th percentile at 30-38% across all file sizes. This 0.4x multiplier avoids reallocation for 95%+ of files.
     let capacity = (context.source_text().len() * 2) / 5;
 
     let mut state = FormatState::new(context, allocator);

crates/oxc_formatter_css/src/format.rs

@@ -49,8 +49,10 @@ pub fn format<'a>(
     let context =
         CssFormatContext::new(options, source, comments, /* template_placeholders */ false);
     let mut state = FormatState::new(context, allocator);
-    // TODO: Use `with_capacity` for perf, like `oxc_formatter` does
-    let mut buffer = VecBuffer::new(&mut state);
+    // Pre-allocate: measured on 616 real-world files (bootstrap, vscode, saleor; css/scss/less),
+    // 0.5x source bytes plus a 1024-element floor for tiny-file spikes avoids reallocation for 98% of the corpus.
+    let capacity = (source.len() / 2).max(1024);
+    let mut buffer = VecBuffer::with_capacity(capacity, &mut state);
 
     write!(&mut buffer, FormatCssRoot { stylesheet: &stylesheet, has_bom, front_matter });
 

crates/oxc_formatter_graphql/src/format.rs

@@ -32,8 +32,10 @@ pub fn format<'a>(
 
     let context = GraphqlFormatContext::new(options, source, comments);
     let mut state = FormatState::new(context, allocator);
-    // TODO: Use `with_capacity` for perf, like `oxc_formatter` does
-    let mut buffer = VecBuffer::new(&mut state);
+    // Pre-allocate: measured on 1,241 real-world files (gitlab operations, github/saleor schemas),
+    // 0.4x source bytes plus a 1024-element floor for small operation documents avoided reallocation for the entire corpus.
+    let capacity = (source.len() * 2 / 5).max(1024);
+    let mut buffer = VecBuffer::with_capacity(capacity, &mut state);
 
     write!(&mut buffer, FormatGraphqlRoot { document, has_bom });
 

crates/oxc_formatter_json/src/format.rs

@@ -35,8 +35,11 @@ pub fn format<'a>(
         parsed.source_offset,
     );
     let mut state = FormatState::new(context, allocator);
-    // TODO: Use `with_capacity` for perf, like `oxc_formatter` does
-    let mut buffer = VecBuffer::new(&mut state);
+    // Pre-allocate: measured on 1,447 real-world files (vscode, saleor, bootstrap),
+    // 0.3x source bytes plus a 1024-element floor for tiny-file spikes (`{}` is 3 elements)
+    // avoids reallocation for 99.5% of the corpus.
+    let capacity = (source_text.len() * 3 / 10).max(1024);
+    let mut buffer = VecBuffer::with_capacity(capacity, &mut state);
 
     // BOM detection runs on the original `source_text`; `wrapped_source` may prepend `(`.
     let has_bom = source_text.starts_with(ZWNBSP);

crates/oxc_formatter_yaml/src/format.rs

@@ -31,8 +31,10 @@ pub fn format<'a>(
     let context =
         YamlFormatContext::new(options, source, comments, print::last_descendant_end(root));
     let mut state = FormatState::new(context, allocator);
-    // TODO: Use `with_capacity` for perf, like `oxc_formatter` does
-    let mut buffer = VecBuffer::new(&mut state);
+    // Pre-allocate: measured on 6,925 real-world files (kubernetes, vscode, saleor, bootstrap),
+    // 0.3x source bytes plus a 1024-element floor for tiny-file spikes avoids reallocation for 99.9% of the corpus.
+    let capacity = (source.len() * 3 / 10).max(1024);
+    let mut buffer = VecBuffer::with_capacity(capacity, &mut state);
 
     write!(&mut buffer, FormatYamlRoot { root, has_bom });