Rule proposal: no-named-export

[fsmaia]

Although it has uncommon usages, it would be nice to have a no-named-export rule to enforce export default only.

This may be useful, for example, when defining that a component file may not expose its helpers, giving this file a single purpose, forcing helpers to be put in a proper file/layer with specific rules and behaviors; and organizing those module exports in an index file.

In a practical example:

// valid
import React from 'react';

const App = () => (<div className="App">App</div>);

export default App;

// valid
import React from 'react';

const title = 'App';

const App = () => (<div className="App">{title}</div>);

export default App;

// invalid
import React from 'react';

export const title = 'App';

const App = () => (<div className="App">{title}</div>);

export default App;

[ljharb]

Since we have no-default, we should also have no-named.