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alias.mjs
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alias.mjs
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import { readFile } from 'node:fs/promises';
import path from 'node:path';
import { pathToFileURL, URL } from 'node:url';
import _get from 'lodash-es/get.js';
const projectRoot = pathToFileURL(`${process.cwd()}/`);
const aliasFieldPaths = {
'package.json': 'aliases',
'tsconfig.json': 'compilerOptions.paths',
};
const aliases = (
await readConfigFile('tsconfig.json')
?? await readConfigFile('package.json')
);
if (!aliases) console.warn(
'Alias loader was registered but no aliases were found in tsconfig.json or package.json.',
'This loader will behave as a noop (but you should probably remove it if you aren’t using it).',
);
export function resolve(specifier, ctx, next) {
return (aliases ? resolveAliases : next)(specifier, ctx, next);
}
export async function resolveAliases(specifier, ctx, next) {
for (const [key, dest] of aliases) {
if (specifier === key) return next(dest, ctx);
if (specifier.startsWith(key)) return next(specifier.replace(key, dest));
}
return next(specifier);
}
export function readConfigFile(filename) {
const filepath = path.join(projectRoot.pathname, filename);
return readFile(filepath)
.then(JSON.parse)
.then((contents) => _get(contents, aliasFieldPaths[filename]))
.then(buildAliasMaps)
.catch((err) => { if (err.code !== 'ENOENT') throw err });
}
function buildAliasMaps(config) {
if (!config) return;
const aliases = new Map();
for (const rawKey of Object.keys(config)) {
const alias = config[rawKey][0];
const isPrefix = rawKey.endsWith('*');
const key = isPrefix ? rawKey.slice(0, -1) /* strip '*' */ : rawKey;
const baseDest = isPrefix ? alias.slice(0, -1) /* strip '*' */ : alias;
const dest = baseDest[0] === '/' || URL.canParse(baseDest)
? baseDest
: (new URL(baseDest, projectRoot)).href;
aliases.set(key, dest);
}
return aliases;
}