fix(parser): add support for empty module declaration (#2834)

Should be merged after #2829, Tried a few times to get it done with
graphite stacking but found no success. I guess it either doesn't work
with forks or It is just a skill issue since I'm not familiar with it.

closes: #2829
closes: #2830

---------

Co-authored-by: Dmytro Maretskyi <maretskii@gmail.com>

crates/oxc_ast/src/ast/ts.rs

@@ -697,7 +697,7 @@ pub struct TSModuleDeclaration<'a> {
     #[cfg_attr(feature = "serialize", serde(flatten))]
     pub span: Span,
     pub id: TSModuleDeclarationName<'a>,
-    pub body: TSModuleDeclarationBody<'a>,
+    pub body: Option<TSModuleDeclarationBody<'a>>,
     /// The keyword used to define this module declaration
     /// ```text
     /// namespace Foo {}

crates/oxc_ast/src/ast_builder.rs

@@ -1273,7 +1273,7 @@ impl<'a> AstBuilder<'a> {
         &self,
         span: Span,
         id: TSModuleDeclarationName<'a>,
-        body: TSModuleDeclarationBody<'a>,
+        body: Option<TSModuleDeclarationBody<'a>>,
         kind: TSModuleDeclarationKind,
         modifiers: Modifiers<'a>,
     ) -> Box<'a, TSModuleDeclaration<'a>> {

crates/oxc_ast/src/visit/visit.rs

@@ -2493,10 +2493,13 @@ pub mod walk {
             TSModuleDeclarationName::StringLiteral(lit) => visitor.visit_string_literal(lit),
         }
         match &decl.body {
-            TSModuleDeclarationBody::TSModuleDeclaration(decl) => {
+            Some(TSModuleDeclarationBody::TSModuleDeclaration(decl)) => {
                 visitor.visit_ts_module_declaration(decl);
             }
-            TSModuleDeclarationBody::TSModuleBlock(block) => visitor.visit_ts_module_block(block),
+            Some(TSModuleDeclarationBody::TSModuleBlock(block)) => {
+                visitor.visit_ts_module_block(block);
+            }
+            None => {}
         }
         visitor.leave_node(kind);
     }

crates/oxc_ast/src/visit/visit_mut.rs

@@ -2694,10 +2694,13 @@ pub mod walk_mut {
             TSModuleDeclarationName::StringLiteral(lit) => visitor.visit_string_literal(lit),
         }
         match &mut decl.body {
-            TSModuleDeclarationBody::TSModuleDeclaration(decl) => {
+            Some(TSModuleDeclarationBody::TSModuleDeclaration(decl)) => {
                 visitor.visit_ts_module_declaration(decl);
             }
-            TSModuleDeclarationBody::TSModuleBlock(block) => visitor.visit_ts_module_block(block),
+            Some(TSModuleDeclarationBody::TSModuleBlock(block)) => {
+                visitor.visit_ts_module_block(block);
+            }
+            None => {}
         }
         visitor.leave_node(kind);
     }

crates/oxc_codegen/src/gen_ts.rs

@@ -539,12 +539,12 @@ impl<'a, const MINIFY: bool> Gen<MINIFY> for TSModuleDeclaration<'a> {
         p.wrap_quote(name, |p, _| p.print_str(name.as_bytes()));
         p.print_hard_space();
         match &self.body {
-            TSModuleDeclarationBody::TSModuleDeclaration(body) => {
+            Some(TSModuleDeclarationBody::TSModuleDeclaration(body)) => {
                 p.print_block_start(body.span.start);
                 body.gen(p, ctx);
                 p.print_block_end(body.span.end);
             }
-            TSModuleDeclarationBody::TSModuleBlock(body) => {
+            Some(TSModuleDeclarationBody::TSModuleBlock(body)) => {
                 p.print_block_start(body.span.start);
                 for item in &body.body {
                     p.print_semicolon_if_needed();
@@ -553,6 +553,7 @@ impl<'a, const MINIFY: bool> Gen<MINIFY> for TSModuleDeclaration<'a> {
                 p.print_semicolon_if_needed();
                 p.print_block_end(body.span.end);
             }
+            None => {}
         }
         if MINIFY {
             p.print_semicolon();

crates/oxc_parser/src/lib.rs

@@ -406,8 +406,8 @@ impl<'a> ParserImpl<'a> {
 
 #[cfg(test)]
 mod test {
-
     use oxc_ast::CommentKind;
+    use std::path::Path;
 
     use super::*;
 
@@ -436,6 +436,15 @@ mod test {
         assert_eq!(ret.errors.first().unwrap().to_string(), "Flow is not supported");
     }
 
+    #[test]
+    fn ts_module_declaration() {
+        let allocator = Allocator::default();
+        let source_type = SourceType::from_path(Path::new("module.ts")).unwrap();
+        let source = "declare module 'test'\n";
+        let ret = Parser::new(&allocator, source, source_type).parse();
+        assert_eq!(ret.errors.len(), 0);
+    }
+
     #[test]
     fn directives() {
         let allocator = Allocator::default();

crates/oxc_parser/src/ts/statement.rs

@@ -212,14 +212,12 @@ impl<'a> ParserImpl<'a> {
 
         let mut statements = self.ast.new_vec();
 
-        if self.at(Kind::LCurly) {
         self.expect(Kind::LCurly)?;
 
         while !self.eat(Kind::RCurly) && !self.at(Kind::Eof) {
             let stmt = self.parse_ts_module_item()?;
             statements.push(stmt);
         }
-        }
 
         Ok(self.ast.ts_module_block(self.end_span(span), statements))
     }
@@ -243,11 +241,14 @@ impl<'a> ParserImpl<'a> {
             let span = self.start_span();
             let decl =
                 self.parse_ts_namespace_or_module_declaration_body(span, kind, Modifiers::empty())?;
-            TSModuleDeclarationBody::TSModuleDeclaration(decl)
+            Some(TSModuleDeclarationBody::TSModuleDeclaration(decl))
-        } else {
+        } else if self.at(Kind::LCurly) {
             let block = self.parse_ts_module_block()?;
             self.asi()?;
-            TSModuleDeclarationBody::TSModuleBlock(block)
+            Some(TSModuleDeclarationBody::TSModuleBlock(block))
+        } else {
+            self.asi()?;
+            None
         };
 
         Ok(self.ast.ts_module_declaration(self.end_span(span), id, body, kind, modifiers))

crates/oxc_transformer/src/typescript/mod.rs

@@ -661,13 +661,14 @@ impl<'a> TypeScript<'a> {
         block: &mut Box<'a, TSModuleDeclaration<'a>>,
     ) -> Statement<'a> {
         let body_statements = match &mut block.body {
-            TSModuleDeclarationBody::TSModuleDeclaration(decl) => {
+            Some(TSModuleDeclarationBody::TSModuleDeclaration(decl)) => {
                 let transformed_module_block = self.transform_ts_module_block(decl);
                 self.ctx.ast.new_vec_single(transformed_module_block)
             }
-            TSModuleDeclarationBody::TSModuleBlock(ts_module_block) => {
+            Some(TSModuleDeclarationBody::TSModuleBlock(ts_module_block)) => {
                 self.ctx.ast.move_statement_vec(&mut ts_module_block.body)
             }
+            None => self.ctx.ast.new_vec(),
         };
 
         let name = block.id.name();