[BUG] I cannot extract-meta of react functional-component, due to empty valueDeclaration.

[junbyeol]

• replace the result of pip list | grep dash below

dash                 2.5.0
dash-core-components 2.0.0
dash-html-components 2.0.0
dash-table           5.0.0

Describe the bug

I cannot extract meta of react functional-component, while class component works well.

 const ExternalShortcut: React.FC<Props> = () => {
   return <div>example</div>
 }; // It doesn't work..

//...

class ExternalShortcut extends React.Component<Props, any> {
  render() {
   return <div>example</div>;
  }
} // It works!

dash/extract-meta.js throws the error.

if (commentSource.valueDeclaration) {
                              ^

TypeError: Cannot read properties of undefined (reading 'valueDeclaration')
    at /Users/devsisters/Development/dashapp-poc-dashboard/src/components/lnb/venv/lib/python3.9/site-packages/dash/extract-meta.js:694:31
    at Array.forEach (<anonymous>)
    at /Users/devsisters/Development/dashapp-poc-dashboard/src/components/lnb/venv/lib/python3.9/site-packages/dash/extract-meta.js:645:17
    at Array.forEach (<anonymous>)
    at gatherComponents (/Users/devsisters/Development/dashapp-poc-dashboard/src/components/lnb/venv/lib/python3.9/site-packages/dash/extract-meta.js:640:33)
    at Object.<anonymous> (/Users/devsisters/Development/dashapp-poc-dashboard/src/components/lnb/venv/lib/python3.9/site-packages/dash/extract-meta.js:754:18)
    at Module._compile (node:internal/modules/cjs/loader:1105:14)
    at Object.Module._extensions..js (node:internal/modules/cjs/loader:1159:10)
    at Module.load (node:internal/modules/cjs/loader:981:32)
    at Function.Module._load (node:internal/modules/cjs/loader:822:12)

This is how I fixed.

// Function components.
                    rootExp = typeSymbol;
//                    rootExp.valueDeclaration = rootExp.declarations[0]; // This line is what I add. This line makes the build of functional component success.
                    commentSource = rootExp.valueDeclaration;
                    if (
                        rootExp.valueDeclaration &&
                        rootExp.valueDeclaration.parent
                    ) {
                        // Function with export later like `const MyComponent = (props) => <></>;`
                        commentSource = getParent(
                            rootExp.valueDeclaration.parent
                        );
                    }

Expected behavior

I expected to extract-meta.js work well for react functional-component.

[T4rk1n]

There is two bug here:

• React.FC<Props> throws the above error
• a function component cannot have empty props but that should be valid (eg; const Component = () => <div>foo</div>) throws:Uncaught TypeError: Cannot convert undefined or null to object