[2.0.0-alpha.5:yarn dev]: Code trasform result contains type definition when transforming .ts file

[6maple]

Code trasform result contains type definition when transform .ts file

When export both type definition and others may cause this bug.
This bug only occurs in yarn dev, yarn build works fine.

After checking file response in Devtool Network, I got:

• main.ts

import {createApp} from "/node_modules/.vite/vue.1a6c6345.js";
import {logPrefix} from "/src/utils/index.ts";
const msg = {
    date: new Date(),
    text: "hello vite2"
};
console.log(logPrefix, msg.text);
createApp({
    render: ()=>null
}).mount("#app");

• utils/index.ts

export * from "/src/utils/types.ts";
export const logPrefix = "user-vite2:";

• utils/types.ts

export interface Message {
  date: Date;
  text: string;
}

Then, I debug vite2.0.0-alpha.5 and found something maybe the reason of bug.

When id is utils/types.ts, transformResult.code is '' and typeof transformResult === 'object' && !transformResult.code will be true, the transform result will be treated as no tramsform applied, so the returned code is source code which contains type definition and cause the error in browser console.

Maybe !transformResult.code can change to transformResult.code === code?

node_modules/vite/dist/node/chunks/dep-95ff8110.js line 66700 to 66723.transformRequest

// transform
const transformStart = Date.now();
const transformResult = await pluginContainer.transform(code, id);
if (transformResult == null ||
    (typeof transformResult === 'object' && !transformResult.code)) {
    // no transform applied, keep code as-is
    isDebug$3 &&
        debugTransform(timeFrom(transformStart) + source.dim(` [skipped] ${prettyUrl}`));
}
else {
    isDebug$3 && debugTransform(`${timeFrom(transformStart)} ${prettyUrl}`);
    if (typeof transformResult === 'object') {
        code = transformResult.code;
        map = transformResult.map;
    }
    else {
        code = transformResult;
    }
}
return (mod.transformResult = {
    code,
    map,
    etag: etag_1(code, { weak: true })
});

Reproduction

https://github.com/6maple/test-vite/tree/vite2.0.0-alpha.5-demo-bug2021.1.1

System Info

• required vite version: 2.0.0-alpha.5
• required Operating System: windows 10
• required Node version: 12.14.1