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feat(next-swc): Implement CJS optimizer (#49972)
### What? Implement a CJS optimizer for next-swc ### Why? x-ref: https://vercel.slack.com/archives/C02HY34AKME/p1684341093462309 Assuming most CJS files are transpiled from ESM, we can mimic tree-shaking using an AST transform. ### How? Closes WEB-1072 Fixes #48469 fix NEXT-1156 --------- Co-authored-by: Shu Ding <[email protected]>
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Original file line number | Diff line number | Diff line change |
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use rustc_hash::{FxHashMap, FxHashSet}; | ||
use serde::Deserialize; | ||
use turbopack_binding::swc::core::{ | ||
common::{util::take::Take, SyntaxContext, DUMMY_SP}, | ||
ecma::{ | ||
ast::{ | ||
CallExpr, Callee, Decl, Expr, Id, Ident, Lit, MemberExpr, MemberProp, Module, | ||
ModuleItem, Pat, Script, Stmt, VarDecl, VarDeclKind, VarDeclarator, | ||
}, | ||
atoms::{Atom, JsWord}, | ||
utils::{prepend_stmts, private_ident, ExprFactory, IdentRenamer}, | ||
visit::{ | ||
as_folder, noop_visit_mut_type, noop_visit_type, Fold, Visit, VisitMut, VisitMutWith, | ||
VisitWith, | ||
}, | ||
}, | ||
}; | ||
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pub fn cjs_optimizer(config: Config, unresolved_ctxt: SyntaxContext) -> impl Fold + VisitMut { | ||
as_folder(CjsOptimizer { | ||
data: State::default(), | ||
packages: config.packages, | ||
unresolved_ctxt, | ||
}) | ||
} | ||
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#[derive(Clone, Debug, Deserialize)] | ||
pub struct Config { | ||
pub packages: FxHashMap<String, PackageConfig>, | ||
} | ||
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#[derive(Clone, Debug, Deserialize)] | ||
#[serde(rename_all = "camelCase")] | ||
pub struct PackageConfig { | ||
pub transforms: FxHashMap<JsWord, JsWord>, | ||
} | ||
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struct CjsOptimizer { | ||
data: State, | ||
packages: FxHashMap<String, PackageConfig>, | ||
unresolved_ctxt: SyntaxContext, | ||
} | ||
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#[derive(Debug, Default)] | ||
struct State { | ||
/// List of `require` calls **which should be replaced**. | ||
/// | ||
/// `(identifier): (module_record)` | ||
imports: FxHashMap<Id, ImportRecord>, | ||
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/// `(module_specifier, property): (identifier)` | ||
replaced: FxHashMap<(Atom, JsWord), Id>, | ||
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extra_stmts: Vec<Stmt>, | ||
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rename_map: FxHashMap<Id, Id>, | ||
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/// Ignored identifiers for `obj` of [MemberExpr]. | ||
ignored: FxHashSet<Id>, | ||
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is_prepass: bool, | ||
} | ||
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#[derive(Debug)] | ||
struct ImportRecord { | ||
module_specifier: Atom, | ||
} | ||
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impl CjsOptimizer { | ||
fn should_rewrite(&self, module_specifier: &str) -> Option<&FxHashMap<JsWord, JsWord>> { | ||
self.packages.get(module_specifier).map(|v| &v.transforms) | ||
} | ||
} | ||
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impl VisitMut for CjsOptimizer { | ||
noop_visit_mut_type!(); | ||
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fn visit_mut_module_items(&mut self, stmts: &mut Vec<ModuleItem>) { | ||
self.data.is_prepass = true; | ||
stmts.visit_mut_children_with(self); | ||
self.data.is_prepass = false; | ||
stmts.visit_mut_children_with(self); | ||
} | ||
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fn visit_mut_expr(&mut self, e: &mut Expr) { | ||
e.visit_mut_children_with(self); | ||
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if let Expr::Member(n) = e { | ||
if let MemberProp::Ident(prop) = &n.prop { | ||
if let Expr::Ident(obj) = &*n.obj { | ||
let key = obj.to_id(); | ||
if self.data.ignored.contains(&key) { | ||
return; | ||
} | ||
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if let Some(record) = self.data.imports.get(&key) { | ||
let mut replaced = false; | ||
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let new_id = self | ||
.data | ||
.replaced | ||
.entry((record.module_specifier.clone(), prop.sym.clone())) | ||
.or_insert_with(|| private_ident!(prop.sym.clone()).to_id()) | ||
.clone(); | ||
|
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if let Some(map) = self.should_rewrite(&record.module_specifier) { | ||
if let Some(renamed) = map.get(&prop.sym) { | ||
replaced = true; | ||
if !self.data.is_prepass { | ||
// Transform as `require('foo').bar` | ||
let var = VarDeclarator { | ||
span: DUMMY_SP, | ||
name: Pat::Ident(new_id.clone().into()), | ||
init: Some(Box::new(Expr::Member(MemberExpr { | ||
span: DUMMY_SP, | ||
obj: Box::new(Expr::Call(CallExpr { | ||
span: DUMMY_SP, | ||
callee: Ident::new( | ||
"require".into(), | ||
DUMMY_SP.with_ctxt(self.unresolved_ctxt), | ||
) | ||
.as_callee(), | ||
args: vec![Expr::Lit(Lit::Str( | ||
renamed.clone().into(), | ||
)) | ||
.as_arg()], | ||
type_args: None, | ||
})), | ||
prop: MemberProp::Ident(Ident::new( | ||
prop.sym.clone(), | ||
DUMMY_SP.with_ctxt(self.unresolved_ctxt), | ||
)), | ||
}))), | ||
definite: false, | ||
}; | ||
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self.data.extra_stmts.push(Stmt::Decl(Decl::Var(Box::new( | ||
VarDecl { | ||
span: DUMMY_SP, | ||
kind: VarDeclKind::Const, | ||
declare: false, | ||
decls: vec![var], | ||
}, | ||
)))); | ||
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*e = Expr::Ident(new_id.into()); | ||
} | ||
} | ||
} | ||
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if !replaced { | ||
self.data.ignored.insert(key); | ||
} | ||
} | ||
} | ||
} | ||
} | ||
} | ||
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fn visit_mut_module(&mut self, n: &mut Module) { | ||
n.visit_children_with(&mut Analyzer { | ||
data: &mut self.data, | ||
in_member_or_var: false, | ||
}); | ||
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n.visit_mut_children_with(self); | ||
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prepend_stmts( | ||
&mut n.body, | ||
self.data.extra_stmts.drain(..).map(ModuleItem::Stmt), | ||
); | ||
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n.visit_mut_children_with(&mut IdentRenamer::new(&self.data.rename_map)); | ||
} | ||
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fn visit_mut_script(&mut self, n: &mut Script) { | ||
n.visit_children_with(&mut Analyzer { | ||
data: &mut self.data, | ||
in_member_or_var: false, | ||
}); | ||
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n.visit_mut_children_with(self); | ||
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prepend_stmts(&mut n.body, self.data.extra_stmts.drain(..)); | ||
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n.visit_mut_children_with(&mut IdentRenamer::new(&self.data.rename_map)); | ||
} | ||
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fn visit_mut_stmt(&mut self, n: &mut Stmt) { | ||
n.visit_mut_children_with(self); | ||
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if let Stmt::Decl(Decl::Var(v)) = n { | ||
if v.decls.is_empty() { | ||
n.take(); | ||
} | ||
} | ||
} | ||
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fn visit_mut_var_declarator(&mut self, n: &mut VarDeclarator) { | ||
n.visit_mut_children_with(self); | ||
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// Find `require('foo')` | ||
if let Some(Expr::Call(CallExpr { | ||
callee: Callee::Expr(callee), | ||
args, | ||
.. | ||
})) = n.init.as_deref() | ||
{ | ||
if let Expr::Ident(ident) = &**callee { | ||
if ident.span.ctxt == self.unresolved_ctxt && ident.sym == *"require" { | ||
if let Some(arg) = args.get(0) { | ||
if let Expr::Lit(Lit::Str(v)) = &*arg.expr { | ||
// TODO: Config | ||
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if let Pat::Ident(name) = &n.name { | ||
if let Some(..) = self.should_rewrite(&v.value) { | ||
let key = name.to_id(); | ||
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if !self.data.is_prepass { | ||
if !self.data.ignored.contains(&key) { | ||
// Drop variable declarator. | ||
n.name.take(); | ||
} | ||
} else { | ||
self.data.imports.insert( | ||
key, | ||
ImportRecord { | ||
module_specifier: v.value.clone().into(), | ||
}, | ||
); | ||
} | ||
} | ||
} | ||
} | ||
} | ||
} | ||
} | ||
} | ||
} | ||
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fn visit_mut_var_declarators(&mut self, n: &mut Vec<VarDeclarator>) { | ||
n.visit_mut_children_with(self); | ||
|
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// We make `name` invalid if we should drop it. | ||
n.retain(|v| !v.name.is_invalid()); | ||
} | ||
} | ||
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struct Analyzer<'a> { | ||
in_member_or_var: bool, | ||
data: &'a mut State, | ||
} | ||
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impl Visit for Analyzer<'_> { | ||
noop_visit_type!(); | ||
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fn visit_var_declarator(&mut self, n: &VarDeclarator) { | ||
self.in_member_or_var = true; | ||
n.visit_children_with(self); | ||
self.in_member_or_var = false; | ||
} | ||
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fn visit_member_expr(&mut self, e: &MemberExpr) { | ||
self.in_member_or_var = true; | ||
e.visit_children_with(self); | ||
self.in_member_or_var = false; | ||
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if let (Expr::Ident(obj), MemberProp::Computed(..)) = (&*e.obj, &e.prop) { | ||
self.data.ignored.insert(obj.to_id()); | ||
} | ||
} | ||
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fn visit_ident(&mut self, i: &Ident) { | ||
i.visit_children_with(self); | ||
if !self.in_member_or_var { | ||
self.data.ignored.insert(i.to_id()); | ||
} | ||
} | ||
} |
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