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Add pure annotation comments for React functions + JSX
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134 changes: 134 additions & 0 deletions
134
ecmascript/transforms/react/src/pure_annotations/mod.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,134 @@ | ||
| use std::collections::HashMap; | ||
| use swc_atoms::{js_word, JsWord}; | ||
| use swc_common::comments::Comments; | ||
| use swc_ecma_ast::*; | ||
| use swc_ecma_utils::{id, Id}; | ||
| use swc_ecma_visit::{Fold, FoldWith}; | ||
|
|
||
| #[cfg(test)] | ||
| mod tests; | ||
|
|
||
| /// This pass adds a /*#__PURE__#/ annotation to calls to known pure top-level | ||
| /// React methods, so that terser and other minifiers can safely remove them | ||
| /// during dead code elimination. | ||
| /// See https://reactjs.org/docs/react-api.html | ||
| pub fn pure_annotations<C>(comments: Option<C>) -> impl Fold | ||
| where | ||
| C: Comments, | ||
| { | ||
| PureAnnotations { | ||
| imports: HashMap::new(), | ||
| comments, | ||
| } | ||
| } | ||
|
|
||
| struct PureAnnotations<C> | ||
| where | ||
| C: Comments, | ||
| { | ||
| imports: HashMap<Id, (JsWord, JsWord)>, | ||
| comments: Option<C>, | ||
| } | ||
|
|
||
| impl<C> Fold for PureAnnotations<C> | ||
| where | ||
| C: Comments, | ||
| { | ||
| fn fold_module(&mut self, module: Module) -> Module { | ||
| // Pass 1: collect imports | ||
| for item in &module.body { | ||
| match item { | ||
| ModuleItem::ModuleDecl(ModuleDecl::Import(import)) => { | ||
| let src_str = import.src.value.to_string(); | ||
| if src_str != "react" && src_str != "react-dom" { | ||
| continue; | ||
| } | ||
|
|
||
| for specifier in &import.specifiers { | ||
| let src = import.src.value.clone(); | ||
| match specifier { | ||
| ImportSpecifier::Named(named) => { | ||
| let imported = match &named.imported { | ||
| Some(imported) => imported.sym.clone(), | ||
| None => named.local.sym.clone(), | ||
| }; | ||
| self.imports.insert(id(&named.local), (src, imported)); | ||
| } | ||
| ImportSpecifier::Default(default) => { | ||
| self.imports | ||
| .insert(id(&default.local), (src, js_word!("default"))); | ||
| } | ||
| ImportSpecifier::Namespace(ns) => { | ||
| self.imports.insert(id(&ns.local), (src, "*".into())); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| _ => {} | ||
| } | ||
| } | ||
|
|
||
| // Pass 2: add pure annotations. | ||
| module.fold_children_with(self) | ||
| } | ||
|
|
||
| fn fold_call_expr(&mut self, call: CallExpr) -> CallExpr { | ||
| let is_react_call = match &call.callee { | ||
| ExprOrSuper::Expr(expr) => match &**expr { | ||
| Expr::Ident(ident) => { | ||
| if let Some((src, specifier)) = self.imports.get(&id(&ident)) { | ||
| is_pure(src, specifier) | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
| Expr::Member(member) => match &member.obj { | ||
| ExprOrSuper::Expr(expr) => match &**expr { | ||
| Expr::Ident(ident) => { | ||
| if let Some((src, specifier)) = self.imports.get(&id(&ident)) { | ||
| let specifier_str = specifier.to_string(); | ||
| if specifier_str == "default" || specifier_str == "*" { | ||
| match &*member.prop { | ||
| Expr::Ident(ident) => is_pure(src, &ident.sym), | ||
| _ => false, | ||
| } | ||
| } else { | ||
| false | ||
| } | ||
| } else { | ||
| false | ||
| } | ||
| } | ||
| _ => false, | ||
| }, | ||
| _ => false, | ||
| }, | ||
| _ => false, | ||
| }, | ||
| _ => false, | ||
| }; | ||
|
|
||
| if is_react_call { | ||
| if let Some(comments) = &self.comments { | ||
| comments.add_pure_comment(call.span.lo); | ||
| } | ||
| } | ||
|
|
||
| call.fold_children_with(self) | ||
| } | ||
| } | ||
|
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| fn is_pure(src: &JsWord, specifier: &JsWord) -> bool { | ||
| match src.to_string().as_str() { | ||
| "react" => match specifier.to_string().as_str() { | ||
| "cloneElement" | "createContext" | "createElement" | "createFactory" | "createRef" | ||
| | "forwardRef" | "isValidElement" | "memo" | "lazy" => true, | ||
| _ => false, | ||
| }, | ||
| "react-dom" => match specifier.to_string().as_str() { | ||
| "createPortal" => true, | ||
| _ => false, | ||
| }, | ||
| _ => false, | ||
| } | ||
| } |
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