refactor(syntax): remove ModuleRecord::export_default (#7578)

This value can be derived.

crates/oxc_linter/src/module_record.rs

@@ -464,7 +464,17 @@ impl ModuleRecord {
                 .iter()
                 .map(|(name, span)| (CompactStr::from(name.as_str()), *span))
                 .collect(),
-            export_default: other.export_default,
+            export_default: other
+                .local_export_entries
+                .iter()
+                .filter_map(|export_entry| export_entry.export_name.default_export_span())
+                .chain(
+                    other
+                        .indirect_export_entries
+                        .iter()
+                        .filter_map(|export_entry| export_entry.export_name.default_export_span()),
+                )
+                .next(),
             ..ModuleRecord::default()
         }
     }

crates/oxc_linter/src/rules/import/no_default_export.rs

@@ -49,9 +49,6 @@ impl Rule for NoDefaultExport {
         if let Some(span) = module_record.export_default {
             ctx.diagnostic(no_default_export_diagnostic(span));
         }
-        if let Some(span) = module_record.exported_bindings.get("default") {
-            ctx.diagnostic(no_default_export_diagnostic(*span));
-        }
     }
 }
 

crates/oxc_parser/src/lib.rs

@@ -438,20 +438,21 @@ impl<'a> ParserImpl<'a> {
                 errors.push(error);
             }
         }
+        let (module_record, module_record_errors) = self.module_record_builder.build();
         if errors.len() != 1 {
             errors.reserve(self.lexer.errors.len() + self.errors.len());
             errors.extend(self.lexer.errors);
             errors.extend(self.errors);
             // Skip checking for exports in TypeScript {
             if !self.source_type.is_typescript() {
-                errors.extend(self.module_record_builder.errors());
+                errors.extend(module_record_errors);
             }
         }
         let irregular_whitespaces =
             self.lexer.trivia_builder.irregular_whitespaces.into_boxed_slice();
         ParserReturn {
             program,
-            module_record: self.module_record_builder.build(),
+            module_record,
             errors,
             irregular_whitespaces,
             panicked,

crates/oxc_parser/src/module_record.rs

@@ -11,7 +11,6 @@ pub struct ModuleRecordBuilder<'a> {
     allocator: &'a Allocator,
     module_record: ModuleRecord<'a>,
     export_entries: Vec<ExportEntry<'a>>,
-    export_default_duplicated: Vec<Span>,
     exported_bindings_duplicated: Vec<NameSpan<'a>>,
 }
 
@@ -21,16 +20,16 @@ impl<'a> ModuleRecordBuilder<'a> {
             allocator,
             module_record: ModuleRecord::new(allocator),
             export_entries: vec![],
-            export_default_duplicated: vec![],
             exported_bindings_duplicated: vec![],
         }
     }
 
-    pub fn build(mut self) -> ModuleRecord<'a> {
+    pub fn build(mut self) -> (ModuleRecord<'a>, Vec<OxcDiagnostic>) {
         // The `ParseModule` algorithm requires `importedBoundNames` (import entries) to be
         // resolved before resolving export entries.
         self.resolve_export_entries();
-        self.module_record
+        let errors = self.errors();
+        (self.module_record, errors)
     }
 
     pub fn errors(&self) -> Vec<OxcDiagnostic> {
@@ -44,19 +43,25 @@ impl<'a> ModuleRecordBuilder<'a> {
             errors.push(diagnostics::duplicate_export(&name_span.name, name_span.span, old_span));
         }
 
-        for span in &self.export_default_duplicated {
-            let old_span = module_record.export_default.unwrap();
-            errors.push(diagnostics::duplicate_export("default", *span, old_span));
-        }
-
-        // `export default x;`
-        // `export { y as default };`
-        if let (Some(span), Some(default_span)) =
-            (module_record.exported_bindings.get("default"), &module_record.export_default)
-        {
-            errors.push(diagnostics::duplicate_export("default", *default_span, *span));
+        // Multiple default exports
+        // `export default foo`
+        // `export { default }`
+        let default_exports = module_record
+            .local_export_entries
+            .iter()
+            .filter_map(|export_entry| export_entry.export_name.default_export_span())
+            .chain(
+                module_record
+                    .indirect_export_entries
+                    .iter()
+                    .filter_map(|export_entry| export_entry.export_name.default_export_span()),
+            )
+            .collect::<Vec<_>>();
+        if default_exports.len() > 1 {
+            errors.push(
+                OxcDiagnostic::error("Duplicated default export").with_labels(default_exports),
+            );
         }
-
         errors
     }
 
@@ -94,12 +99,6 @@ impl<'a> ModuleRecordBuilder<'a> {
         }
     }
 
-    fn add_default_export(&mut self, span: Span) {
-        if let Some(old_node) = self.module_record.export_default.replace(span) {
-            self.export_default_duplicated.push(old_node);
-        }
-    }
-
     /// [ParseModule](https://tc39.es/ecma262/#sec-parsemodule)
     /// Step 10.
     fn resolve_export_entries(&mut self) {
@@ -264,8 +263,6 @@ impl<'a> ModuleRecordBuilder<'a> {
             return;
         }
         let exported_name = &decl.exported;
-        let exported_name_span = decl.exported.span();
-        self.add_default_export(exported_name_span);
 
         let local_name = match &decl.declaration {
             ExportDefaultDeclarationKind::Identifier(ident) => {

crates/oxc_syntax/src/module_record.rs

@@ -55,10 +55,6 @@ pub struct ModuleRecord<'a> {
 
     /// Local exported bindings
     pub exported_bindings: FxHashMap<Atom<'a>, Span>,
-
-    /// `export default name`
-    ///         ^^^^^^^ span
-    pub export_default: Option<Span>,
 }
 
 impl<'a> ModuleRecord<'a> {
@@ -72,7 +68,6 @@ impl<'a> ModuleRecord<'a> {
             indirect_export_entries: Vec::new_in(allocator),
             star_export_entries: Vec::new_in(allocator),
             exported_bindings: FxHashMap::default(),
-            export_default: None,
         }
     }
 }
@@ -287,6 +282,17 @@ impl ExportExportName<'_> {
             Self::Null => None,
         }
     }
+
+    /// Get default export span
+    /// `export default foo`
+    /// `export { default }`
+    pub fn default_export_span(&self) -> Option<Span> {
+        match self {
+            Self::Default(span) => Some(*span),
+            Self::Name(name_span) if name_span.name == "default" => Some(name_span.span),
+            _ => None,
+        }
+    }
 }
 
 /// `LocalName` for `ExportEntry`

tasks/coverage/snapshots/parser_babel.snap

@@ -3031,24 +3031,20 @@ Expect to Parse: tasks/coverage/babel/packages/babel-parser/test/fixtures/typesc
    ·                    ───────────
    ╰────
 
-  × Duplicated export 'default'
+  × Duplicated default export
    ╭─[babel/packages/babel-parser/test/fixtures/es2015/modules/duplicate-export-default/input.js:1:8]
  1 │ export default {};
-   ·        ───┬───
-   ·           ╰── Export has already been declared here
+   ·        ───────
  2 │ export default function() {};
-   ·        ───┬───
-   ·           ╰── It cannot be redeclared here
+   ·        ───────
    ╰────
 
-  × Duplicated export 'default'
+  × Duplicated default export
    ╭─[babel/packages/babel-parser/test/fixtures/es2015/modules/duplicate-export-default-and-export-as-default/input.js:1:8]
  1 │ export default function() {};
-   ·        ───┬───
-   ·           ╰── Export has already been declared here
+   ·        ───────
  2 │ export { foo as default };
-   ·                 ───┬───
-   ·                    ╰── It cannot be redeclared here
+   ·                 ───────
    ╰────
 
   × Export 'foo' is not defined

tasks/coverage/snapshots/parser_test262.snap

@@ -22158,15 +22158,13 @@ Expect Syntax Error: tasks/coverage/test262/test/language/import/import-attribut
     ·                  ╰── It can not be redeclared here
     ╰────
 
-  × Duplicated export 'default'
+  × Duplicated default export
     ╭─[test262/test/language/module-code/early-dup-export-dflt-id.js:18:8]
  17 │ var x, y;
  18 │ export default x;
-    ·        ───┬───
-    ·           ╰── Export has already been declared here
+    ·        ───────
  19 │ export { y as default };
-    ·               ───┬───
-    ·                  ╰── It cannot be redeclared here
+    ·               ───────
     ╰────
 
   × Unexpected token
@@ -22199,15 +22197,13 @@ Expect Syntax Error: tasks/coverage/test262/test/language/import/import-attribut
     ·          ╰── It cannot be redeclared here
     ╰────
 
-  × Duplicated export 'default'
+  × Duplicated default export
     ╭─[test262/test/language/module-code/early-dup-export-star-as-dflt.js:18:8]
  17 │ var x;
  18 │ export default x;
-    ·        ───┬───
-    ·           ╰── Export has already been declared here
+    ·        ───────
  19 │ export * as default from './early-dup-export-start-as-dflt.js';
-    ·             ───┬───
-    ·                ╰── It cannot be redeclared here
+    ·             ───────
     ╰────
 
   × Label `label` has already been declared

tasks/coverage/snapshots/parser_typescript.snap

@@ -22418,14 +22418,12 @@ Expect to Parse: tasks/coverage/typescript/tests/cases/conformance/salsa/private
  13 │     deleted() {
     ╰────
 
-  × Duplicated export 'default'
+  × Duplicated default export
    ╭─[typescript/tests/cases/conformance/salsa/plainJSBinderErrors.ts:1:8]
  1 │ export default 12
-   ·        ───┬───
-   ·           ╰── Export has already been declared here
+   ·        ───────
  2 │ export default 13
-   ·        ───┬───
-   ·           ╰── It cannot be redeclared here
+   ·        ───────
  3 │ const await = 1
    ╰────