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Merged
merged 2 commits into from
Aug 7, 2025
Merged

perf: reduce heap allocations and memory creating cjs wrapper module #30344

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perf: reduce heap allocations creating cjs wrapper module
dsherret Aug 7, 2025
0f0c5f7
lint
dsherret Aug 7, 2025
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2 changes: 2 additions & 0 deletions Cargo.lock
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2 changes: 1 addition & 1 deletion cli/factory.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1142,7 +1142,7 @@ impl CliFactory {
},
node_code_translator_mode: match options.sub_command() {
DenoSubcommand::Bundle(_) => {
node_resolver::analyze::NodeCodeTranslatorMode::Bundling
node_resolver::analyze::NodeCodeTranslatorMode::Disabled
}
_ => node_resolver::analyze::NodeCodeTranslatorMode::ModuleLoader,
},
Expand Down
2 changes: 2 additions & 0 deletions libs/node_resolver/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ sync = ["deno_package_json/sync"]
anyhow.workspace = true
async-trait.workspace = true
boxed_error.workspace = true
capacity_builder.workspace = true
dashmap.workspace = true
deno_config.workspace = true
deno_error.workspace = true
Expand All @@ -33,6 +34,7 @@ futures.workspace = true
lazy-regex.workspace = true
once_cell.workspace = true
path-clean.workspace = true
pretty_assertions.workspace = true
regex.workspace = true
serde.workspace = true
serde_json.workspace = true
Expand Down
190 changes: 113 additions & 77 deletions libs/node_resolver/analyze.rs
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Expand Up @@ -555,7 +555,7 @@ pub struct NodeCodeTranslator<

#[derive(Debug, Default, Clone, Copy)]
pub enum NodeCodeTranslatorMode {
Bundling,
Disabled,
#[default]
ModuleLoader,
}
Expand Down Expand Up @@ -602,8 +602,7 @@ impl<
entry_specifier: &Url,
source: Option<Cow<'a, str>>,
) -> Result<Cow<'a, str>, TranslateCjsToEsmError> {
let all_exports = if matches!(self.mode, NodeCodeTranslatorMode::Bundling) {
// let the bundler handle it instead of the module loader
let all_exports = if matches!(self.mode, NodeCodeTranslatorMode::Disabled) {
return Ok(source.unwrap());
} else {
let analysis = self
Expand All @@ -616,48 +615,10 @@ impl<
ResolvedCjsAnalysis::Cjs(all_exports) => all_exports,
}
};

// todo(dsherret): use capacity_builder here to remove all these heap
// allocations and make the string writing faster
let mut temp_var_count = 0;
let mut source = vec![
r#"import {createRequire as __internalCreateRequire, Module as __internalModule } from "node:module";
const require = __internalCreateRequire(import.meta.url);"#
.to_string(),
];

source.push(format!(
r#"let mod;
if (import.meta.main) {{
mod = __internalModule._load("{0}", null, true)
}} else {{
mod = require("{0}");
}}"#,
url_to_file_path(entry_specifier)
.unwrap()
.to_str()
.unwrap()
.replace('\\', "\\\\")
.replace('\'', "\\\'")
.replace('\"', "\\\"")
));

for export in &all_exports {
if !matches!(export.as_str(), "default" | "module.exports") {
add_export(
&mut source,
export,
&format!("mod[{}]", to_double_quote_string(export)),
&mut temp_var_count,
);
}
}

source.push("export default mod;".to_string());
add_export(&mut source, "module.exports", "mod", &mut temp_var_count);

let translated_source = source.join("\n");
Ok(Cow::Owned(translated_source))
Ok(Cow::Owned(exports_to_wrapper_module(
entry_specifier,
&all_exports,
)))
}
}

Expand Down Expand Up @@ -734,10 +695,69 @@ static RESERVED_WORDS: Lazy<HashSet<&str>> = Lazy::new(|| {
])
});

fn add_export(
source: &mut Vec<String>,
name: &str,
initializer: &str,
fn exports_to_wrapper_module(
entry_specifier: &Url,
all_exports: &BTreeSet<String>,
) -> String {
let quoted_entry_specifier_text = to_double_quote_string(
url_to_file_path(entry_specifier).unwrap().to_str().unwrap(),
);
let export_names_with_quoted = all_exports
.iter()
.map(|export| (export.as_str(), to_double_quote_string(export)))
.collect::<Vec<_>>();
capacity_builder::StringBuilder::<String>::build(|builder| {
let mut temp_var_count = 0;
builder.append(
r#"import { createRequire as __internalCreateRequire, Module as __internalModule } from "node:module";
const require = __internalCreateRequire(import.meta.url);
let mod;
if (import.meta.main) {
mod = __internalModule._load("#,
);
builder.append(&quoted_entry_specifier_text);
builder.append(
r#", null, true)
} else {
mod = require("#,
);
builder.append(&quoted_entry_specifier_text);
builder.append(r#");
}
"#);

for (export_name, quoted_name) in &export_names_with_quoted {
if !matches!(*export_name, "default" | "module.exports") {
add_export(
builder,
export_name,
quoted_name,
|builder| {
builder.append("mod[");
builder.append(quoted_name);
builder.append("]");
},
&mut temp_var_count,
);
}
}

builder.append("export default mod;\n");
add_export(
builder,
"module.exports",
"\"module.exports\"",
|builder| builder.append("mod"),
&mut temp_var_count,
);
}).unwrap()
}

fn add_export<'a>(
builder: &mut capacity_builder::StringBuilder<'a, String>,
name: &'a str,
quoted_name: &'a str,
build_initializer: impl FnOnce(&mut capacity_builder::StringBuilder<'a, String>),
temp_var_count: &mut usize,
) {
fn is_valid_var_decl(name: &str) -> bool {
Expand All @@ -764,15 +784,21 @@ fn add_export(
// we can't create an identifier with a reserved word or invalid identifier name,
// so assign it to a temporary variable that won't have a conflict, then re-export
// it as a string
source.push(format!(
"const __deno_export_{temp_var_count}__ = {initializer};"
));
source.push(format!(
"export {{ __deno_export_{temp_var_count}__ as {} }};",
to_double_quote_string(name)
));
builder.append("const __deno_export_");
builder.append(*temp_var_count);
builder.append("__ = ");
build_initializer(builder);
builder.append(";\nexport { __deno_export_");
builder.append(*temp_var_count);
builder.append("__ as ");
builder.append(quoted_name);
builder.append(" };\n");
} else {
source.push(format!("export const {name} = {initializer};"));
builder.append("export const ");
builder.append(name);
builder.append(" = ");
build_initializer(builder);
builder.append(";\n");
}
}

Expand All @@ -783,30 +809,40 @@ fn to_double_quote_string(text: &str) -> String {

#[cfg(test)]
mod tests {
use pretty_assertions::assert_eq;

use super::*;

#[test]
fn test_add_export() {
let mut temp_var_count = 0;
let mut source = vec![];

let exports = vec!["static", "server", "app", "dashed-export", "3d"];
for export in exports {
add_export(&mut source, export, "init", &mut temp_var_count);
}
fn test_exports_to_wrapper_module() {
let url = Url::parse("file:///test/test.ts").unwrap();
let exports = BTreeSet::from(
["static", "server", "app", "dashed-export", "3d"].map(|s| s.to_string()),
);
let text = exports_to_wrapper_module(&url, &exports);
assert_eq!(
source,
vec![
"const __deno_export_1__ = init;".to_string(),
"export { __deno_export_1__ as \"static\" };".to_string(),
"export const server = init;".to_string(),
"export const app = init;".to_string(),
"const __deno_export_2__ = init;".to_string(),
"export { __deno_export_2__ as \"dashed-export\" };".to_string(),
"const __deno_export_3__ = init;".to_string(),
"export { __deno_export_3__ as \"3d\" };".to_string(),
]
)
text,
r#"import { createRequire as __internalCreateRequire, Module as __internalModule } from "node:module";
const require = __internalCreateRequire(import.meta.url);
let mod;
if (import.meta.main) {
mod = __internalModule._load("/test/test.ts", null, true)
} else {
mod = require("/test/test.ts");
}
const __deno_export_1__ = mod["3d"];
export { __deno_export_1__ as "3d" };
export const app = mod["app"];
const __deno_export_2__ = mod["dashed-export"];
export { __deno_export_2__ as "dashed-export" };
export const server = mod["server"];
const __deno_export_3__ = mod["static"];
export { __deno_export_3__ as "static" };
export default mod;
const __deno_export_4__ = mod;
export { __deno_export_4__ as "module.exports" };
"#
);
}

#[test]
Expand Down
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