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index.js
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index.js
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import { declare } from "@babel/helper-plugin-utils";
import { types as t } from "@babel/core";
function getName(key) {
if (t.isIdentifier(key)) {
return key.name;
}
return key.value.toString();
}
export default declare(api => {
api.assertVersion(7);
return {
name: "transform-duplicate-keys",
visitor: {
ObjectExpression(path) {
const { node } = path;
const plainProps = node.properties.filter(
prop => !t.isSpreadElement(prop) && !prop.computed,
);
// A property is a duplicate key if:
// * the property is a data property, and is preceded by a data,
// getter, or setter property of the same name.
// * the property is a getter property, and is preceded by a data or
// getter property of the same name.
// * the property is a setter property, and is preceded by a data or
// setter property of the same name.
const alreadySeenData = Object.create(null);
const alreadySeenGetters = Object.create(null);
const alreadySeenSetters = Object.create(null);
for (const prop of plainProps) {
const name = getName(prop.key);
let isDuplicate = false;
switch (prop.kind) {
case "get":
if (alreadySeenData[name] || alreadySeenGetters[name]) {
isDuplicate = true;
}
alreadySeenGetters[name] = true;
break;
case "set":
if (alreadySeenData[name] || alreadySeenSetters[name]) {
isDuplicate = true;
}
alreadySeenSetters[name] = true;
break;
default:
if (
alreadySeenData[name] ||
alreadySeenGetters[name] ||
alreadySeenSetters[name]
) {
isDuplicate = true;
}
alreadySeenData[name] = true;
}
if (isDuplicate) {
// Rely on the computed properties transform to split the property
// assignment out of the object literal.
prop.computed = true;
prop.key = t.stringLiteral(name);
}
}
},
},
};
});