packages/babel-helper-split-export-declaration/src/index.js
import * as t from "@babel/types";
export default function splitExportDeclaration(exportDeclaration) {
if (!exportDeclaration.isExportDeclaration()) {
throw new Error("Only export declarations can be splitted.");
}
// build specifiers that point back to this export declaration
const isDefault = exportDeclaration.isExportDefaultDeclaration();
const declaration = exportDeclaration.get("declaration");
const isClassDeclaration = declaration.isClassDeclaration();
if (isDefault) {
const standaloneDeclaration =
declaration.isFunctionDeclaration() || isClassDeclaration;
const scope = declaration.isScope()
? declaration.scope.parent
: declaration.scope;
let id = declaration.node.id;
let needBindingRegistration = false;
if (!id) {
needBindingRegistration = true;
id = scope.generateUidIdentifier("default");
if (
standaloneDeclaration ||
declaration.isFunctionExpression() ||
declaration.isClassExpression()
) {
declaration.node.id = t.cloneNode(id);
}
}
const updatedDeclaration = standaloneDeclaration
? declaration
: t.variableDeclaration("var", [
t.variableDeclarator(t.cloneNode(id), declaration.node),
]);
const updatedExportDeclaration = t.exportNamedDeclaration(null, [
t.exportSpecifier(t.cloneNode(id), t.identifier("default")),
]);
exportDeclaration.insertAfter(updatedExportDeclaration);
exportDeclaration.replaceWith(updatedDeclaration);
if (needBindingRegistration) {
scope.registerDeclaration(exportDeclaration);
}
return exportDeclaration;
}
if (exportDeclaration.get("specifiers").length > 0) {
throw new Error("It doesn't make sense to split exported specifiers.");
}
const bindingIdentifiers = declaration.getOuterBindingIdentifiers();
const specifiers = Object.keys(bindingIdentifiers).map(name => {
return t.exportSpecifier(t.identifier(name), t.identifier(name));
});
const aliasDeclar = t.exportNamedDeclaration(null, specifiers);
exportDeclaration.insertAfter(aliasDeclar);
exportDeclaration.replaceWith(declaration.node);
return exportDeclaration;
}