nstdlib-nightly/lib/internal/modules/esm/initialize_import_meta.mjs

Node.js standard library converted to runtime-agnostic ES modules.

// Source: https://github.com/nodejs/node/blob/65eff1eb/lib/internal/modules/esm/initialize_import_meta.js

import { getOptionValue } from "nstdlib/lib/internal/options";
import { fileURLToPath } from "nstdlib/lib/internal/url";
import { dirname } from "nstdlib/lib/path";

const experimentalImportMetaResolve = getOptionValue(
  "--experimental-import-meta-resolve",
);

/**
 * Generate a function to be used as import.meta.resolve for a particular module.
 * @param {string} defaultParentURL The default base to use for resolution
 * @param {typeof import('./loader.js').ModuleLoader} loader Reference to the current module loader
 * @param {bool} allowParentURL Whether to permit parentURL second argument for contextual resolution
 * @returns {(specifier: string) => string} Function to assign to import.meta.resolve
 */
function createImportMetaResolve(defaultParentURL, loader, allowParentURL) {
  /**
   * @param {string} specifier
   * @param {URL['href']} [parentURL] When `--experimental-import-meta-resolve` is specified, a
   * second argument can be provided.
   */
  return function resolve(specifier, parentURL = defaultParentURL) {
    let url;

    if (!allowParentURL) {
      parentURL = defaultParentURL;
    }

    try {
      ({ url } = loader.resolveSync(specifier, parentURL));
      return url;
    } catch (error) {
      switch (error?.code) {
        case "ERR_UNSUPPORTED_DIR_IMPORT":
        case "ERR_MODULE_NOT_FOUND":
          ({ url } = error);
          if (url) {
            return url;
          }
      }
      throw error;
    }
  };
}

/**
 * Create the `import.meta` object for a module.
 * @param {object} meta
 * @param {{url: string}} context
 * @param {typeof import('./loader.js').ModuleLoader} loader Reference to the current module loader
 * @returns {{dirname?: string, filename?: string, url: string, resolve?: Function}}
 */
function initializeImportMeta(meta, context, loader) {
  const { url } = context;

  // Alphabetical
  if (String.prototype.startsWith.call(url, "file:") === true) {
    // These only make sense for locally loaded modules,
    // i.e. network modules are not supported.
    const filePath = fileURLToPath(url);
    meta.dirname = dirname(filePath);
    meta.filename = filePath;
  }

  if (!loader || loader.allowImportMetaResolve) {
    meta.resolve = createImportMetaResolve(
      url,
      loader,
      experimentalImportMetaResolve,
    );
  }

  meta.url = url;

  return meta;
}

export { initializeImportMeta };