fune/toolkit/components/normandy/lib/PrefUtils.jsm

/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";

const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
const { XPCOMUtils } = ChromeUtils.import(
  "resource://gre/modules/XPCOMUtils.jsm"
);
ChromeUtils.defineModuleGetter(
  this,
  "LogManager",
  "resource://normandy/lib/LogManager.jsm"
);

var EXPORTED_SYMBOLS = ["PrefUtils"];

XPCOMUtils.defineLazyGetter(this, "log", () => {
  return LogManager.getLogger("preference-experiments");
});

const kPrefBranches = {
  user: Services.prefs,
  default: Services.prefs.getDefaultBranch(""),
};

var PrefUtils = {
  /**
   * Get a preference of any type from the named branch.
   * @param {string} pref
   * @param {object} [options]
   * @param {"default"|"user"} [options.branchName="user"] One of "default" or "user"
   * @param {string|boolean|integer|null} [options.defaultValue]
   *   The value to return if the preference does not exist. Defaults to null.
   */
  getPref(pref, { branch = "user", defaultValue = null } = {}) {
    const branchObj = kPrefBranches[branch];
    if (!branchObj) {
      throw new this.UnexpectedPreferenceBranch(
        `"${branch}" is not a valid preference branch`
      );
    }
    const type = branchObj.getPrefType(pref);

    try {
      switch (type) {
        case Services.prefs.PREF_BOOL: {
          return branchObj.getBoolPref(pref);
        }
        case Services.prefs.PREF_STRING: {
          return branchObj.getStringPref(pref);
        }
        case Services.prefs.PREF_INT: {
          return branchObj.getIntPref(pref);
        }
        case Services.prefs.PREF_INVALID: {
          return defaultValue;
        }
      }
    } catch (e) {
      if (branch === "default" && e.result === Cr.NS_ERROR_UNEXPECTED) {
        // There is a value for the pref on the user branch but not on the default branch. This is ok.
        return defaultValue;
      }
      // Unexpected error, re-throw it
      throw e;
    }

    // If `type` isn't any of the above, throw an error. Don't do this in a
    // default branch of switch so that error handling is easier.
    throw new TypeError(`Unknown preference type (${type}) for ${pref}.`);
  },

  /**
   * Set a preference on the named branch
   * @param {string} pref
   * @param {string|boolean|integer|null} value The value to set.
   * @param {object} options
   * @param {"user"|"default"} options.branchName The branch to make the change on.
   */
  setPref(pref, value, { branch = "user" } = {}) {
    if (value === null) {
      this.clearPref(pref, { branch });
      return;
    }
    const branchObj = kPrefBranches[branch];
    if (!branchObj) {
      throw new this.UnexpectedPreferenceBranch(
        `"${branch}" is not a valid preference branch`
      );
    }
    switch (typeof value) {
      case "boolean": {
        branchObj.setBoolPref(pref, value);
        break;
      }
      case "string": {
        branchObj.setStringPref(pref, value);
        break;
      }
      case "number": {
        branchObj.setIntPref(pref, value);
        break;
      }
      default: {
        throw new TypeError(
          `Unexpected value type (${typeof value}) for ${pref}.`
        );
      }
    }
  },

  /**
   * Remove a preference from a branch. Note that default branch preferences
   * cannot effectively be cleared. If "default" is passed for a branch, an
   * error will be logged and nothing else will happen.
   *
   * @param {string} pref
   * @param {object} options
   * @param {"user"|"default"} options.branchName The branch to clear
   */
  clearPref(pref, { branch = "user" } = {}) {
    if (branch === "user") {
      kPrefBranches.user.clearUserPref(pref);
    } else if (branch === "default") {
      log.warn(
        `Cannot reset pref ${pref} on the default branch. Pref will be cleared at next restart.`
      );
    } else {
      throw new this.UnexpectedPreferenceBranch(
        `"${branch}" is not a valid preference branch`
      );
    }
  },

  UnexpectedPreferenceType: class extends Error {},
  UnexpectedPreferenceBranch: class extends Error {},
};