Remove this exports tracking for files with module syntax (#9330)

Co-authored-by: Devon Govett <[email protected]>

Author: mattcompiles

packages/core/integration-tests/test/scope-hoisting.js

@@ -17,6 +17,7 @@ import {
   overlayFS,
   run,
   runBundle,
+  fsFixture,
 } from '@parcel/test-utils';
 
 const bundle = (name, opts = {}) => {
@@ -2487,6 +2488,23 @@ describe('scope hoisting', function () {
       assert.equal(await output, 42);
     });
 
+    it('should handle TSC polyfills', async () => {
+      await fsFixture(overlayFS, __dirname)`
+        tsc-polyfill-es6
+          library.js:
+            var __polyfill = (this && this.__polyfill) || function (a) {return a;};
+            export default __polyfill('es6')
+
+          index.js:
+            import value from './library';
+            output = value;`;
+
+      let b = await bundle(path.join(__dirname, 'tsc-polyfill-es6/index.js'), {
+        inputFS: overlayFS,
+      });
+      assert.equal(await run(b), 'es6');
+    });
+
     describe("considers an asset's closest package.json for sideEffects, not the package through which it found the asset", () => {
       it('handles redirects up the tree', async () => {
         let b = await bundle(
@@ -5265,6 +5283,29 @@ describe('scope hoisting', function () {
 
       assert.deepEqual(await run(b), {test: 2});
     });
+
+    it('should handle TSC polyfills', async () => {
+      await fsFixture(overlayFS, __dirname)`
+        tsc-polyfill-commonjs
+          library.js:
+            "use strict";
+            var __polyfill = (this && this.__polyfill) || function (a) {return a;};
+            exports.value = __polyfill('cjs')
+
+          index.js:
+            const value = require('./library');
+            output = value;
+      `;
+
+      let b = await bundle(
+        path.join(__dirname, 'tsc-polyfill-commonjs/index.js'),
+        {
+          inputFS: overlayFS,
+        },
+      );
+
+      assert.deepEqual(await run(b), {value: 'cjs'});
+    });
   });
 
   it('should not throw with JS included from HTML', async function () {

packages/transformers/js/core/src/collect.rs

@@ -78,6 +78,7 @@ pub struct Collect {
   in_function: bool,
   in_assign: bool,
   in_class: bool,
+  is_module: bool,
 }
 
 #[derive(Debug, Serialize)]
@@ -120,12 +121,14 @@ impl Collect {
     ignore_mark: Mark,
     global_mark: Mark,
     trace_bailouts: bool,
+    is_module: bool,
   ) -> Self {
     Collect {
       source_map,
       decls,
       ignore_mark,
       global_mark,
+      is_module,
       static_cjs_exports: true,
       has_cjs_exports: false,
       is_esm: false,
@@ -690,7 +693,9 @@ impl Visit for Collect {
       }
       Expr::This(_this) => {
         if self.in_module_this {
-          handle_export!();
+          if !self.is_module {
+            handle_export!();
+          }
         } else if !self.in_class {
           if let MemberProp::Ident(prop) = &node.prop {
             self.this_exprs.insert(id!(prop), (prop.clone(), node.span));
@@ -767,27 +772,6 @@ impl Visit for Collect {
           self.used_imports.insert(id!(ident));
         }
       }
-      Expr::Bin(bin_expr) => {
-        if self.in_module_this {
-          // Some TSC polyfills use a pattern like below.
-          // We want to avoid marking these modules as CJS
-          // e.g. var _polyfill = (this && this.polyfill) || function () {}
-          if matches!(bin_expr.op, BinaryOp::LogicalAnd) && matches!(*bin_expr.left, Expr::This(..))
-          {
-            match &*bin_expr.right {
-              Expr::Member(member_expr) => {
-                if matches!(*member_expr.obj, Expr::This(..))
-                  && matches!(member_expr.prop, MemberProp::Ident(..))
-                {
-                  return;
-                }
-              }
-              _ => {}
-            }
-          }
-        }
-        node.visit_children_with(self);
-      }
       _ => {
         node.visit_children_with(self);
       }
@@ -820,7 +804,7 @@ impl Visit for Collect {
   }
 
   fn visit_this_expr(&mut self, node: &ThisExpr) {
-    if self.in_module_this {
+    if !self.is_module && self.in_module_this {
       self.has_cjs_exports = true;
       self.static_cjs_exports = false;
       self.add_bailout(node.span, BailoutReason::FreeExports);

packages/transformers/js/core/src/fs.rs

@@ -17,6 +17,7 @@ pub fn inline_fs<'a>(
   global_mark: Mark,
   project_root: &'a str,
   deps: &'a mut Vec<DependencyDescriptor>,
+  is_module: bool,
 ) -> impl Fold + 'a {
   InlineFS {
     filename: Path::new(filename).to_path_buf(),
@@ -26,6 +27,7 @@ pub fn inline_fs<'a>(
       Mark::fresh(Mark::root()),
       global_mark,
       false,
+      is_module,
     ),
     global_mark,
     project_root,

packages/transformers/js/core/src/hoist.rs

@@ -1140,11 +1140,21 @@ mod tests {
     );
 
     let mut parser = Parser::new_from(lexer);
-    match parser.parse_module() {
-      Ok(module) => swc_core::common::GLOBALS.set(&Globals::new(), || {
+    match parser.parse_program() {
+      Ok(program) => swc_core::common::GLOBALS.set(&Globals::new(), || {
         swc_core::ecma::transforms::base::helpers::HELPERS.set(
           &swc_core::ecma::transforms::base::helpers::Helpers::new(false),
           || {
+            let is_module = program.is_module();
+            let module = match program {
+              Program::Module(module) => module,
+              Program::Script(script) => Module {
+                span: script.span,
+                shebang: None,
+                body: script.body.into_iter().map(ModuleItem::Stmt).collect(),
+              },
+            };
+
             let unresolved_mark = Mark::fresh(Mark::root());
             let global_mark = Mark::fresh(Mark::root());
             let module = module.fold_with(&mut resolver(unresolved_mark, global_mark, false));
@@ -1155,6 +1165,7 @@ mod tests {
               Mark::fresh(Mark::root()),
               global_mark,
               true,
+              is_module,
             );
             module.visit_with(&mut collect);
 
@@ -1444,6 +1455,7 @@ mod tests {
     // We want to avoid marking these modules as CJS
     let (collect, _code, _hoist) = parse(
       r#"
+      import 'something';
       var __classPrivateFieldSet = (this && this.__classPrivateFieldSet) || function () {}
     "#,
     );

packages/transformers/js/core/src/lib.rs

@@ -252,6 +252,7 @@ pub fn transform(config: Config) -> Result<TransformResult, std::io::Error> {
                 ),
               ));
 
+              let is_module = module.is_module();
               // If it's a script, convert into module. This needs to happen after
               // the resolver (which behaves differently for non-/strict mode).
               let module = match module {
@@ -342,6 +343,7 @@ pub fn transform(config: Config) -> Result<TransformResult, std::io::Error> {
                       global_mark,
                       &config.project_root,
                       &mut fs_deps,
+                      is_module
                     ),
                     should_inline_fs
                   ),
@@ -448,6 +450,7 @@ pub fn transform(config: Config) -> Result<TransformResult, std::io::Error> {
                 ignore_mark,
                 global_mark,
                 config.trace_bailouts,
+                is_module,
               );
               module.visit_with(&mut collect);
               if let Some(bailouts) = &collect.bailouts {