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index.js
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index.js
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const nodePath = require('path');
const callerCallsite = require('caller-callsite');
let BuiltinModule = require('module');
// Guard against poorly mocked module constructors
let Module = module.constructor.length > 1
? module.constructor
: BuiltinModule;
// --- Module folder paths ---
let modulePaths = [];
let oldNodeModulePaths = Module._nodeModulePaths;
Module._nodeModulePaths = function(from) {
let paths = oldNodeModulePaths.call(this, from);
// Only include the module path for top-level modules
// that were not installed:
if (from.indexOf('node_modules') === -1)
paths = modulePaths.concat(paths);
return paths;
}
function addPathHelper(path, targetArray) {
path = nodePath.normalize(path);
if (targetArray && targetArray.indexOf(path) === -1)
targetArray.unshift(path);
}
function addPath(path) {
path = nodePath.normalize(path);
// Return if path is already added
if (modulePaths.indexOf(path) !== -1)
return;
modulePaths.push(path);
// Enable the search path for the current top-level module
let mainModule = require.main._simulateRepl ? undefined : require.main;
if (mainModule)
addPathHelper(path, mainModule.paths);
// Also modify the paths of the module that was used to load the
// path-alias module and all of it's parents
let parent = module.parent;
while (parent && parent !== mainModule) {
addPathHelper(path, parent.paths);
parent = parent.parent;
}
}
// --- Path aliases ---
let pathAliases = {};
let pathAliasNames = [];
function addAlias(alias, target) {
// Allow object of aliases to be passed
if (typeof alias == 'object' && typeof target == 'undefined') {
for (let thisAlias in alias)
addAlias(thisAlias, alias[thisAlias]);
return;
}
pathAliases[alias] = target;
// Cost of sorting is lower here than during resolution
pathAliasNames = Object.keys(pathAliases);
pathAliasNames.sort().reverse();
}
function removeAlias(...alias) {
for (let i = 0; i < alias.length; i++) {
if (Array.isArray(alias[i])) {
removeAlias(...alias[i]);
continue;
}
delete pathAliases[alias[i]];
}
pathAliasNames = Object.keys(pathAliases);
pathAliasNames.sort().reverse();
}
function pathContainsAlias(path, alias) {
// Matching /^alias(\/|$)/
return (path.indexOf(alias) === 0 && (path.length === alias.length || path[alias.length] === '/'));
}
function resolve(path) {
for (let i = 0; i < pathAliasNames.length; i++) {
const alias = pathAliasNames[i];
if (!pathContainsAlias(path, alias))
continue;
let aliasTarget = pathAliases[alias];
// Custom function handler
if (typeof aliasTarget === 'function') {
aliasTarget = aliasTarget(callerCallsite({ recentFirst: true, depth: 1 }).getFileName(), path, alias);
if (!aliasTarget || typeof aliasTarget !== 'string')
throw new Error('[path-alias] Expecting custom handler function to return path.');
}
return nodePath.join(aliasTarget, path.substr(alias.length));
}
// If no alias matches, return supplied path
return path;
}
let oldResolveFilename = Module._resolveFilename;
Module._resolveFilename = function(request, parentModule, isMain, options) {
request = resolve(request);
return oldResolveFilename.call(this, request, parentModule, isMain, options);
}
const exportObj = {
addPath,
addAlias,
removeAlias,
resolve,
pathContainsAlias,
// Added to not have any breaking differences between this module and the module it's based off of, module-alias
isPathMatchesAlias: pathContainsAlias,
addAliases: addAlias,
removeAliases: removeAlias,
};
/**
* Import aliases from package.json
* @param {object} options
*/
function init(options) {
if (typeof options === 'string') {
options = { base: options };
}
options = options || {};
// There is probably 99% chance that the project root directory is located
// above the node_modules directory,
// Or that package.json is in the node process' current working directory (when
// running a package manager script, e.g. `yarn start` / `npm run start`)
let candidatePackagePaths = options.base ?
[nodePath.resolve(options.base.replace(/\/package\.json$/, ''))] :
[nodePath.join(__dirname, '..', '..'), process.cwd()];
let base;
let npmPackage;
for (let i in candidatePackagePaths) {
try {
base = candidatePackagePaths[i];
npmPackage = require(nodePath.join(base, 'package.json'));
break;
} catch (e) {}
}
if (typeof npmPackage !== 'object') {
let pathString = candidatePackagePaths.join(',\n');
throw new Error(`[path-alias] Unable to find package.json in any of:\n[${pathString}]`);
}
// Import aliases, fallback to _moduleAliases if needed
let aliases = npmPackage._pathAliases || npmPackage._moduleAliases || {};
for (let alias in aliases)
if (aliases[alias][0] !== '/')
aliases[alias] = nodePath.join(base, aliases[alias]);
addAlias(aliases);
// Register custom module directories (like node_modules)
if (npmPackage._moduleDirectories instanceof Array) {
npmPackage._moduleDirectories.forEach(function(dir) {
if (dir === 'node_modules')
return;
let modulePath = nodePath.join(base, dir);
addPath(modulePath);
});
}
return exportObj;
}
module.exports = init;
Object.assign(module.exports, exportObj);