elm-pages/generator/src/vite-utils.js

Hybrid Elm framework with full-stack and static routes.

/** This code is from https://github.com/sveltejs/kit/blob/3b457f67d4d7c59fc63bb3f600a490e4dacc2e62/packages/kit/src/exports/vite/utils.js */

/**
 * @param {...import('vite').UserConfig} configs
 * @returns {import('vite').UserConfig}
 */
export function merge_vite_configs(...configs) {
  return deep_merge(
    ...configs.map((config) => ({
      ...config,
      resolve: {
        ...config.resolve,
        alias: normalize_alias((config.resolve && config.resolve.alias) || {}),
      },
    }))
  );
}

/**
 * Takes zero or more objects and returns a new object that has all the values
 * deeply merged together. None of the original objects will be mutated at any
 * level, and the returned object will have no references to the original
 * objects at any depth. If there's a conflict the last one wins, except for
 * arrays which will be combined.
 * @param {...Object} objects
 * @returns {Record<string, any>} the merged object
 */
function deep_merge(...objects) {
  const result = {};
  /** @type {string[]} */
  objects.forEach((o) => merge_into(result, o));
  return result;
}

/**
 * normalize kit.vite.resolve.alias as an array
 * @param {import('vite').AliasOptions} o
 * @returns {import('vite').Alias[]}
 */
function normalize_alias(o) {
  if (Array.isArray(o)) return o;
  return Object.entries(o).map(([find, replacement]) => ({
    find,
    replacement,
  }));
}

/**
 * Merges b into a, recursively, mutating a.
 * @param {Record<string, any>} a
 * @param {Record<string, any>} b
 */
function merge_into(a, b) {
  /**
   * Checks for "plain old Javascript object", typically made as an object
   * literal. Excludes Arrays and built-in types like Buffer.
   * @param {any} x
   */
  const is_plain_object = (x) =>
    typeof x === "object" && x.constructor === Object;

  for (const prop in b) {
    if (is_plain_object(b[prop])) {
      if (!is_plain_object(a[prop])) {
        a[prop] = {};
      }
      merge_into(a[prop], b[prop]);
    } else if (Array.isArray(b[prop])) {
      if (!Array.isArray(a[prop])) {
        a[prop] = [];
      }
      a[prop].push(...b[prop]);
    } else {
      a[prop] = b[prop];
    }
  }
}