An app that broken after 2.0.0-beta.51

[sibbng]

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• Use Vite >=2.0. (1.x is no longer supported)
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Describe the bug

Unfortunately I can't describe the error while vite is not giving me any error message. But I tried to be specific as much as I can in reproduction section.

Reproduction

This is the demo app used for https://github.com/antfu/reactivue.

Reproduction: https://github.com/sibbng/vite-issue-repro

version	yarn dev	yarn build && yarn serve
2.0.0-beta.50	works	works
2.0.0-beta.51	doesn't work. no errors from vite itself. just reactivue errors.	works
2.0.0-beta.52	doesn't work. no errors from vite itself. just reactivue errors.	works
2.0.0-beta.53	Invalid loader: "mjs"	works

Note:

• On beta.50 my entry script in index.html was like that: src="src/index.tsx". beta.51 didn't allow that entry and throw an error. I fixed it by putting slash at the beginning src="/src/index.tsx" .
• beta.53 error:
  

System Info

• vite version: 2.0.0-beta.51
• Operating System: Windows 10
• Node version: v14.15.4
• Package manager (npm/yarn/pnpm) and version: yarn

Logs (Optional if provided reproduction)

1. Run vite or vite build with the --debug flag.
2. Provide the error log here.

[vtenfys]

I'm also seeing this error in 2.0.0-beta.53 and 2.0.0-beta.54:

22:59:28 [vite] new dependencies found: @prefresh/vite/runtime, @prefresh/vite/utils, updating...
 > error: [JavaScript plugins] Invalid loader: "mjs" (valid: js, jsx, ts, tsx, css, json, text, base64, dataurl, file, binary)

 > error: [JavaScript plugins] Invalid loader: "mjs" (valid: js, jsx, ts, tsx, css, json, text, base64, dataurl, file, binary)

22:59:28 [vite] error while updating dependencies:
Error: Build failed with 2 errors:
error: [JavaScript plugins] Invalid loader: "mjs" (valid: js, jsx, ts, tsx, css, json, text, base64, dataurl, file, binary)
error: [JavaScript plugins] Invalid loader: "mjs" (valid: js, jsx, ts, tsx, css, json, text, base64, dataurl, file, binary)
    at failureErrorWithLog (/Users/david/Code/my-project/node_modules/esbuild/lib/main.js:969:15)
    at buildResponseToResult (/Users/david/Code/my-project/node_modules/esbuild/lib/main.js:767:32)
    at /Users/david/Code/my-project/node_modules/esbuild/lib/main.js:819:20
    at handleIncomingPacket (/Users/david/Code/my-project/node_modules/esbuild/lib/main.js:566:9)
    at Socket.readFromStdout (/Users/david/Code/my-project/node_modules/esbuild/lib/main.js:482:7)
    at Socket.emit (node:events:379:20)
    at addChunk (node:internal/streams/readable:313:12)
    at readableAddChunk (node:internal/streams/readable:288:9)
    at Socket.Readable.push (node:internal/streams/readable:227:10)
    at Pipe.onStreamRead (node:internal/stream_base_commons:190:23)