refactor(rsc): move common code for transformCjsToEsm (#909)

Author: hi-ogawa

packages/plugin-rsc/src/plugins/cjs.ts

@@ -54,14 +54,6 @@ export function cjsModuleRunnerPlugin(): Plugin[] {
           const ast = await parseAstAsync(code)
           const result = transformCjsToEsm(code, ast)
           const output = result.output
-          // TODO: can we use cjs-module-lexer to properly define named exports?
-          // for re-exports, we need to eagerly transform dependencies though.
-          // https://github.com/nodejs/node/blob/f3adc11e37b8bfaaa026ea85c1cf22e3a0e29ae9/lib/internal/modules/esm/translators.js#L382-L409
-          output.append(`
-;__vite_ssr_exportAll__(module.exports);
-export default module.exports;
-export const __cjs_module_runner_transform = true;
-`)
           return {
             code: output.toString(),
             map: output.generateMap({ hires: 'boundary' }),

packages/plugin-rsc/src/transforms/cjs.test.ts

@@ -24,6 +24,10 @@ exports.ok = true;
     expect(await testTransform(input)).toMatchInlineSnapshot(`
       "let exports = {}; const module = { exports };
       exports.ok = true;
+
+      ;__vite_ssr_exportAll__(module.exports);
+      export default module.exports;
+      export const __cjs_module_runner_transform = true;
       "
     `)
   })
@@ -44,6 +48,10 @@ if (true) {
       } else {
         module.exports = (__cjs_interop__(await import('./cjs/use-sync-external-store.development.js')));
       }
+
+      ;__vite_ssr_exportAll__(module.exports);
+      export default module.exports;
+      export const __cjs_module_runner_transform = true;
       "
     `)
   })
@@ -66,6 +74,10 @@ if (true) {
         var ReactDOM = __cjs_to_esm_hoist_1;
         exports.useSyncExternalStoreWithSelector = function () {}
       })()
+
+      ;__vite_ssr_exportAll__(module.exports);
+      export default module.exports;
+      export const __cjs_module_runner_transform = true;
       "
     `)
   })
@@ -97,6 +109,10 @@ function test() {
         const y2 = __cjs_to_esm_hoist_1().test;
         consoe.log(__cjs_to_esm_hoist_2)
       }
+
+      ;__vite_ssr_exportAll__(module.exports);
+      export default module.exports;
+      export const __cjs_module_runner_transform = true;
       "
     `)
   })
@@ -114,6 +130,10 @@ function test() {
         const require = () => {};
         require("test");
       }
+
+      ;__vite_ssr_exportAll__(module.exports);
+      export default module.exports;
+      export const __cjs_module_runner_transform = true;
       "
     `)
   })
@@ -130,11 +150,6 @@ function test() {
             if (id.endsWith('.cjs')) {
               const ast = await parseAstAsync(code)
               const { output } = transformCjsToEsm(code, ast)
-              output.append(`
-;__vite_ssr_exportAll__(module.exports);
-export default module.exports;
-export const __cjs_module_runner_transform = true;
-`)
               return {
                 code: output.toString(),
                 map: output.generateMap({ hires: 'boundary' }),

packages/plugin-rsc/src/transforms/cjs.ts

@@ -75,6 +75,7 @@ export function transformCjsToEsm(
       parentNodes.pop()!
     },
   })
+  // TODO: prepend after shebang
   for (const hoisted of hoistedCodes.reverse()) {
     output.prepend(hoisted)
   }
@@ -83,5 +84,15 @@ export function transformCjsToEsm(
   }
   // https://nodejs.org/docs/v22.19.0/api/modules.html#exports-shortcut
   output.prepend(`let exports = {}; const module = { exports };\n`)
+
+  // TODO: can we use cjs-module-lexer to properly define named exports?
+  // for re-exports, we need to eagerly transform dependencies though.
+  // https://github.com/nodejs/node/blob/f3adc11e37b8bfaaa026ea85c1cf22e3a0e29ae9/lib/internal/modules/esm/translators.js#L382-L409
+  output.append(`
+;__vite_ssr_exportAll__(module.exports);
+export default module.exports;
+export const __cjs_module_runner_transform = true;
+`)
+
   return { output }
 }