[Bug]: Storybook couldn't evaluate your .storybook/main.ts file

[leosvelperez]

Describe the bug

With the new 0.21.0 version, an error is thrown when trying to process the main.ts file. See the logs below:

$ storybook dev -p 6006
@storybook/core v8.5.0-beta.3

SB_CORE-SERVER_0007 (MainFileEvaluationError): Storybook couldn't evaluate your .storybook/main.ts file.

Original error:
Error: Transform failed with 1 error:
(define name):1:0: ERROR: Expected identifier but found "import"
    at failureErrorWithLog (/node_modules/esbuild/lib/main.js:1466:15)
    at eval (/node_modules/esbuild/lib/main.js:745:50)
    at responseCallbacks.<computed> (/node_modules/esbuild/lib/main.js:612:9)
    at handleIncomingPacket (/node_modules/esbuild/lib/main.js:667:12)
    at Socket.readFromStdout (/node_modules/esbuild/lib/main.js:590:7)
    at Socket.emit (node:events:30:10899)
    at addChunk (node:internal/streams/readable:225:3685)
    at readableAddChunk (node:internal/streams/readable:225:3393)
    at Readable.push (node:internal/streams/readable:225:4971)
    at _0x50b08f.onStreamRead (node:internal/stream_base_commons:211:2596)
    at failureErrorWithLog (/node_modules/esbuild/lib/main.js:1466:15)
    at eval (/node_modules/esbuild/lib/main.js:745:50)
    at responseCallbacks.<computed> (/node_modules/esbuild/lib/main.js:612:9)
    at handleIncomingPacket (/node_modules/esbuild/lib/main.js:667:12)
    at Socket.readFromStdout (/node_modules/esbuild/lib/main.js:590:7)
    at Socket.emit (node:events:30:10899)
    at addChunk (node:internal/streams/readable:225:3685)
    at readableAddChunk (node:internal/streams/readable:225:3393)
    at Readable.push (node:internal/streams/readable:225:4971)
    at _0x50b08f.onStreamRead (node:internal/stream_base_commons:211:2596)
    at new StorybookError (./node_modules/@storybook/core/dist/server-errors.cjs:177:5)
    at new MainFileEvaluationError (./node_modules/@storybook/core/dist/server-errors.cjs:577:5)
    at loadMainConfig (./node_modules/@storybook/core/dist/common/index.cjs:17515:11)
    at async buildDevStandalone (./node_modules/@storybook/core/dist/core-server/index.cjs:37142:11)
    at async withTelemetry (./node_modules/@storybook/core/dist/core-server/index.cjs:35765:12)
    at async dev (./node_modules/@storybook/core/dist/cli/bin/index.cjs:2591:3)
    at async s.eval (./node_modules/@storybook/core/dist/cli/bin/index.cjs:2643:74)

WARN Broken build, fix the error above.
WARN You may need to refresh the browser.

To Reproduce

The default template with Next.js shows the problem: https://stackblitz.com/github/storybookjs/sandboxes/tree/next/nextjs/default-ts/after-storybook. Check the terminal.

System

Storybook Environment Info:

  System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 18.20.3 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.2.3 - /usr/local/bin/npm <----- active
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    @storybook/addon-essentials: ^8.5.0-beta.3 => 8.5.0-beta.3 
    @storybook/addon-interactions: ^8.5.0-beta.3 => 8.5.0-beta.3 
    @storybook/addon-onboarding: ^8.5.0-beta.3 => 8.5.0-beta.3 
    @storybook/blocks: ^8.5.0-beta.3 => 8.5.0-beta.3 
    @storybook/nextjs: ^8.5.0-beta.3 => 8.5.0-beta.3 
    @storybook/react: ^8.5.0-beta.3 => 8.5.0-beta.3 
    @storybook/test: ^8.5.0-beta.3 => 8.5.0-beta.3 
    storybook: ^8.5.0-beta.3 => 8.5.0-beta.3

Additional context

No response