Most developers have encountered the puzzling error message: “Plugin/preset files are not allowed to export objects, only functions.” This notification typically arises when you are working with tools like Babel or Webpack, which rely on plugins and presets to effectively transpile and bundle your JavaScript code. Understanding this error is important to preventing disruptions in your development workflow and ensuring that your build process runs smoothly.
When you configure a plugin or preset for Babel, you may unintentionally export an object instead of a function. Plugins and presets in Babel are designed to be initialized as functions that return an object representing the transformations. This is crucial because Babel needs to call these functions during the transpilation process. When Babel encounters an exported object instead of executing a function, it cannot apply the transformations and hence throws an error, halting your build.
To fix this issue, start by examining the file that is generating the error. You should verify the syntax of your exports. Make sure that if you’re exporting a plugin or a preset, you use a function appropriately. A basic structure for a Babel plugin looks like this:
module.exports = function(babel) {
return {
visitor: {
Identifier(path) {
// Transformations logic goes here
}
}
};
};
Alternatively, if you are configuring a preset, it should still be a function, typically like this:
module.exports = function(api) {
api.cache(true); // Caching can improve performance
return {
presets: [
'@babel/preset-env',
'@babel/preset-react',
],
};
};
By ensuring that you are exporting a function instead of an object, you prevent the error while maintaining the expected functionality. If your code seems fine but the error persists, ensure that the versions of Babel, its presets, and plugins are compatible with each other. Mismatched versions can often lead to unexpected errors, including this one.
It’s also a good practice to consult the documentation of the plugins and presets you are using. There are often detailed guides and examples that can clarify how to properly structure your exports. Look for sections that specify the expected format, as this can save you time and effort in troubleshooting.
In summation, if you run into the “Plugin/preset files are not allowed to export objects, only functions” error, you should check that you are correctly exporting a function, not an object. It’s also advisable to verify version compatibility and consult the relevant documentation. Make these adjustments, and you should find that your development experience improves significantly as your code compiles successfully.
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