From d633b2dd1b8157d52c7e74089ebcb3a6959e2859 Mon Sep 17 00:00:00 2001
From: sapphi-red <49056869+sapphi-red@users.noreply.github.com>
Date: Thu, 26 Feb 2026 23:09:44 +0900
Subject: [PATCH 1/2] feat(babel): format babel errors

---
 packages/babel/src/index.test.ts | 21 +++++++++++++++++++++
 packages/babel/src/index.ts      | 21 ++++++++++++++++-----
 2 files changed, 37 insertions(+), 5 deletions(-)

diff --git a/packages/babel/src/index.test.ts b/packages/babel/src/index.test.ts
index 63b3cf9..4887cf3 100644
--- a/packages/babel/src/index.test.ts
+++ b/packages/babel/src/index.test.ts
@@ -549,6 +549,27 @@ describe('per-environment state isolation', () => {
   })
 })
 
+test('babel syntax error produces enhanced error message', async () => {
+  const err = await build('foo.js', 'export const = ;', {
+    plugins: [identifierReplaceBabelPlugin('foo', true)],
+  }).catch((e) => e)
+  const normalized = err.message
+    .replace(/\r\n/g, '\n')
+    .replace(/[A-Z]:[\\/][^\s:]+[\\/](?=foo\.js)/gi, '<cwd>/')
+    .replace(/\n {4,}at .+/g, '')
+    .replace(/\nCaused by:\n[\s\S]*$/, '')
+    .trim()
+  expect(normalized).toMatchInlineSnapshot(`
+    "Build failed with 1 error:
+
+    [plugin @rolldown/plugin-babel] foo.js:1:13
+    RolldownError: [BabelError] <cwd>/foo.js: Unexpected token (1:13)
+
+    > 1 | export const = ;
+        |              ^"
+  `)
+})
+
 async function buildWithVite(
   filename: string,
   code: string,
diff --git a/packages/babel/src/index.ts b/packages/babel/src/index.ts
index 7767961..e7f4707 100644
--- a/packages/babel/src/index.ts
+++ b/packages/babel/src/index.ts
@@ -82,11 +82,22 @@ async function babelPlugin(rawOptions: PluginOptions): Promise<Plugin> {
           return
         }
 
-        const result = await babel.transformAsync(
-          code,
-          // oxlint-disable-next-line typescript/no-unsafe-type-assertion
-          loadedOptions as unknown as babel.InputOptions,
-        )
+        let result: babel.FileResult | null
+        try {
+          result = await babel.transformAsync(
+            code,
+            // oxlint-disable-next-line typescript/no-unsafe-type-assertion
+            loadedOptions as unknown as babel.InputOptions,
+          )
+        } catch (err: any) {
+          this.error({
+            message: `[BabelError] ${err.message}`,
+            loc: err.loc,
+            pos: err.pos,
+            cause: err,
+            pluginCode: `${err.code}:${err.reasonCode}`,
+          })
+        }
         if (result) {
           return {
             code: result.code ?? undefined,

From 6897c46633be21a43cc738f0d517148270bfdfef Mon Sep 17 00:00:00 2001
From: sapphi-red <49056869+sapphi-red@users.noreply.github.com>
Date: Thu, 26 Feb 2026 23:11:11 +0900
Subject: [PATCH 2/2] chore: fix

---
 packages/babel/src/index.test.ts | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/babel/src/index.test.ts b/packages/babel/src/index.test.ts
index 4887cf3..37143b1 100644
--- a/packages/babel/src/index.test.ts
+++ b/packages/babel/src/index.test.ts
@@ -555,7 +555,7 @@ test('babel syntax error produces enhanced error message', async () => {
   }).catch((e) => e)
   const normalized = err.message
     .replace(/\r\n/g, '\n')
-    .replace(/[A-Z]:[\\/][^\s:]+[\\/](?=foo\.js)/gi, '<cwd>/')
+    .replace(/(?:[A-Z]:)?[\\/][^\s:]+[\\/](?=foo\.js)/gi, '<cwd>/')
     .replace(/\n {4,}at .+/g, '')
     .replace(/\nCaused by:\n[\s\S]*$/, '')
     .trim()