Bug: Components inside typescript namespaces cause ReferenceError

[Enteleform]

Forwarded from vitejs/vite#3900 by @not-rusty based on the recommendation of @sodatea, which stated that this should be considered as a bug in the react-refresh package.
 

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Describe the bug

Apparently components inside namespaces is not supported. I don't exactly know if the error comes from esbuild or something, but it would nice.

The bug is that is not shown as a compilation error.

Reproduction

Simply start a react-ts project with $ npm init @vitejs/app my-vue-app --template react-ts and write the following code:

namespace Lol {
  export const Lol = () ={
    return (
      <div>
        <p>Some component</p>
      </div>
    );
  };
}

function App() {
  return (
    <div className="App">
      <header className="App-header">
        <Lol.Lol />
        <p>Hello Vite + React!</p>
      </header>
    </div>
  );
}

export default App;

System Info

  System:
    OS: Linux 5.8 Ubuntu 20.04.2 LTS (Focal Fossa)
    CPU: (8) x64 Intel(R) Core(TM) i5-10210U CPU @ 1.60GHz
    Memory: 440.54 MB / 7.47 GB
    Container: Yes
    Shell: 5.8 - /usr/bin/zsh
  Binaries:
    Node: 14.16.0 - /usr/local/bin/node
    npm: 6.14.13 - /usr/local/bin/npm
  Browsers:
    Chrome: 90.0.4430.93
    Firefox: 89.0.1

Used package manager: npm

Logs

I get the following runtime error:

App.tsx:13 Uncaught ReferenceError: _c is not defined
    at App.tsx:13
    at App.tsx:14

I suppose it should be a compilation error?

[irinakk]

To add more details, namespace with a capitalized function member is transformed into this piece of code:

var N;
(function(N2) {
  N2.Test = () => {
  };
  _c = N2.Test; // Uncaught ReferenceError: _c is not defined
})(N || (N = {}));

The error occurs in vite's development mode since the application code is imported via <script type="module">, which creates strict mode.

[bvaughn]

cc @gaearon To confirm if this is a known/expected limitation.

[todd-elvers]

I have also encountered this error using Vite & react-refresh on a TypeScript react app that has react components nested under namespaces

[gaearon]

To confirm if this is a known/expected limitation.

No, it's not expected. This seems like a bug in the transform.

Transform: https://github.com/facebook/react/blob/main/packages/react-refresh/src/ReactFreshBabelPlugin.js

Tests:

• https://github.com/facebook/react/blob/main/packages/react-refresh/src/__tests__/ReactFreshIntegration-test.js
• https://github.com/facebook/react/blob/main/packages/react-refresh/src/__tests__/ReactFreshBabelPlugin-test.js

If somebody wants to take this one, the first step is to produce a failing integration test demonstrating the issue. (Using compiled TS output as the "source" is fine.)

[owen-kosman]

@gaearon I see that no one has started work on this issue, I'll have a crack at this.

[ideffix]

@owen-kosman @gaearon I digged in a little bit into this issue and it looks like it only happends when code with namespace keyword is being passed to react-refresh/babel so I think it's not possible to reproduce it using just JS (so it's hard to write unit/integration tests). Check code where I present difference between TS compiled code and code that includes namespace.

I manage to fix it but I haven't add any tests because of issue mentioned above. If it's fine here is PR #22601

[irinakk]

@ideffix Hi I think your fix does not solve the real problem here. I digged a little more and found that in this specific babel config in this issue.

const babelOpts = {
  parserOpts: {
    plugins: ["jsx", "typescript"]
  },
  plugins: [["react-refresh/babel.js"]]
};

this line of code gives a false assumption.

  case 'ExportNamedDeclaration':
    insertAfterPath = path.parentPath;
    programPath = insertAfterPath.parentPath; // => error here, this one is not Program
    break;

It seems babel parses namespace syntax into a structure with Program ->TSModuleDeclaration -> TSModuleBlock -> ExportNamedDeclaration, which in normal function exports we would expect Program -> ExportNamedDeclaration.

So I think the fix should be related, i'm not familiar with babel parser and not sure the best way to fix this, but hope the info helps.

[gaearon]

Should be fixed in [email protected]. Please ask Vite to upgrade and see if that fixes it.