From 2e78b918d1f5dcd0fb4928840506c8e084c488ad Mon Sep 17 00:00:00 2001
From: Dunqing <dengqing0821@gmail.com>
Date: Thu, 18 Jan 2024 21:28:48 +0800
Subject: [PATCH] refactor(transformer/typescript): move the
 ExportNamedDeclaration logic to its function (#2074)

---
 crates/oxc_transformer/src/typescript/mod.rs | 96 +++++++++++---------
 1 file changed, 54 insertions(+), 42 deletions(-)

diff --git a/crates/oxc_transformer/src/typescript/mod.rs b/crates/oxc_transformer/src/typescript/mod.rs
index b527f0ab5..3f662918d 100644
--- a/crates/oxc_transformer/src/typescript/mod.rs
+++ b/crates/oxc_transformer/src/typescript/mod.rs
@@ -49,53 +49,21 @@ impl<'a> TypeScript<'a> {
         }
     }
 
-    /// Remove `export` from merged declaration.
-    /// We only preserve the first one.
-    /// for example:
-    /// ```TypeScript
-    /// export enum Foo {}
-    /// export enum Foo {}
-    /// ```
-    /// ```JavaScript
-    /// export enum Foo {}
-    /// enum Foo {}
-    /// ```
     pub fn transform_statement(&mut self, stmt: &mut Statement<'a>) {
-        let Statement::ModuleDeclaration(module_decl) = stmt else {
-            return;
-        };
-
-        let ModuleDeclaration::ExportNamedDeclaration(export_decl) = &mut **module_decl else {
-            return;
-        };
-
-        let ExportNamedDeclaration {
-            declaration: Some(declaration),
-            source: None,
-            export_kind: ImportOrExportKind::Value,
-            ..
-        } = &mut **export_decl
-        else {
-            return;
-        };
-
-        let id = match &declaration {
-            Declaration::TSEnumDeclaration(decl) => decl.id.name.clone(),
-            Declaration::TSModuleDeclaration(decl) => {
-                let TSModuleDeclarationName::Identifier(id) = &decl.id else {
-                    return;
-                };
-
-                id.name.clone()
+        let new_stmt = match stmt {
+            Statement::ModuleDeclaration(module_decl) => {
+                if let ModuleDeclaration::ExportNamedDeclaration(decl) = &mut **module_decl {
+                    self.transform_export_named_declaration(decl)
+                } else {
+                    None
+                }
             }
-            _ => return,
+            _ => None,
         };
 
-        if self.export_name_set.insert(id) {
-            return;
+        if let Some(new_stmt) = new_stmt {
+            *stmt = new_stmt;
         }
-
-        *stmt = Statement::Declaration(self.ast.move_declaration(declaration));
     }
 
     /// * Remove the top level import / export statements that are types
@@ -550,4 +518,48 @@ impl<'a> TypeScript<'a> {
 
         Some(Declaration::VariableDeclaration(variable_declaration))
     }
+
+    /// Remove `export` from merged declaration.
+    /// We only preserve the first one.
+    /// for example:
+    /// ```TypeScript
+    /// export enum Foo {}
+    /// export enum Foo {}
+    /// ```
+    /// ```JavaScript
+    /// export enum Foo {}
+    /// enum Foo {}
+    /// ```
+    fn transform_export_named_declaration(
+        &mut self,
+        decl: &mut Box<'_, ExportNamedDeclaration<'a>>,
+    ) -> Option<Statement<'a>> {
+        let ExportNamedDeclaration {
+            declaration: Some(declaration),
+            source: None,
+            export_kind: ImportOrExportKind::Value,
+            ..
+        } = &mut **decl
+        else {
+            return None;
+        };
+
+        let id = match &declaration {
+            Declaration::TSEnumDeclaration(decl) => decl.id.name.clone(),
+            Declaration::TSModuleDeclaration(decl) => {
+                let TSModuleDeclarationName::Identifier(id) = &decl.id else {
+                    return None;
+                };
+
+                id.name.clone()
+            }
+            _ => return None,
+        };
+
+        if self.export_name_set.insert(id) {
+            return None;
+        }
+
+        Some(Statement::Declaration(self.ast.move_declaration(declaration)))
+    }
 }