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const tests = {
// ECMAScript 2018
"object-rest-spread": ["({ ...{} })", "({ ...x } = {})"], // Babel 7.2.0
"async-generators": ["async function* f() {}"], // Babel 7.2.0
// ECMAScript 2019
"optional-catch-binding": ["try {} catch {}"], // Babel 7.2.0
"json-strings": ["'\\u2028'"], // Babel 7.2.0
// ECMAScript 2020
"bigint": ["1n"], // Babel 7.8.0
"optional-chaining": ["a?.b"], // Babel 7.9.0
"nullish-coalescing-operator": ["a ?? b"], // Babel 7.9.0
// import.meta is handled manually
// Stage 3
"numeric-separator": ["1_2"],
"class-properties": [
"(class { x = 1 })",
"(class { #x = 1 })",
"(class { #x() {} })",
],
"logical-assignment-operators": ["a ||= b", "a &&= b", "a ??= c"],
};
const plugins = [];
const works = (test) => {
try {
// Wrap the test in a function to only test the syntax, without executing it
(0, eval)(`(() => { ${test} })`);
return true;
} catch (_error) {
return false;
}
};
for (const [name, cases] of Object.entries(tests)) {
if (cases.some(works)) {
plugins.push(require.resolve(`@babel/plugin-syntax-${name}`));
}
}
// import.meta is only allowed in modules, and modules can only be evaluated
// synchronously. For this reason, we cannot detect import.meta support at
// runtime. It is supported starting from 10.4, so we can check the version.
const major = parseInt(process.versions.node, 10);
const minor = parseInt(process.versions.node.match(/^\d+\.(\d+)/)[1], 10);
if (major > 10 || (major === 10 && minor >= 4)) {
plugins.push(require.resolve("@babel/plugin-syntax-import-meta"));
}
// Same for top level await - it is only supported in modules. It is supported
// from 14.3.0
if (major > 14 || (major === 14 && minor >= 3)) {
plugins.push(require.resolve("@babel/plugin-syntax-top-level-await"));
}
module.exports = () => ({ plugins });
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