How to use the @expo/config.configFilename function in @expo/config

const expJsonExists = await fileExistsAsync(path.join(projectRoot, 'exp.json'));
  const appJsonExists = await fileExistsAsync(path.join(projectRoot, 'app.json'));

  if (expJsonExists && appJsonExists) {
    ProjectUtils.logWarning(
      projectRoot,
      'expo',
      `Warning: Both app.json and exp.json exist in this directory. Only one should exist for a single project.`,
      'doctor-both-app-and-exp-json'
    );
    return WARNING;
  }
  ProjectUtils.clearNotification(projectRoot, 'doctor-both-app-and-exp-json');

  let sdkVersion = exp.sdkVersion;
  const configName = configFilename(projectRoot);

  // Warn if sdkVersion is UNVERSIONED
  if (sdkVersion === 'UNVERSIONED' && !process.env.EXPO_SKIP_MANIFEST_VALIDATION_TOKEN) {
    ProjectUtils.logError(
      projectRoot,
      'expo',
      `Error: Using unversioned Expo SDK. Do not publish until you set sdkVersion in ${configName}`,
      'doctor-unversioned'
    );
    return ERROR;
  }
  ProjectUtils.clearNotification(projectRoot, 'doctor-unversioned');
  let sdkVersions = await Versions.sdkVersionsAsync();
  if (!sdkVersions) {
    ProjectUtils.logError(
      projectRoot,

projectRoot: string,
  options: {
    current?: boolean;
    mode?: string;
    platform?: 'android' | 'ios' | 'all';
    expIds?: Array;
    type?: string;
    releaseChannel?: string;
    bundleIdentifier?: string;
    publicUrl?: string;
  } = {}
) {
  if (!options.publicUrl) {
    // get the manifest from the project directory
    const { exp, pkg } = await readConfigJsonAsync(projectRoot);
    const configName = configFilename(projectRoot);
    return {
      exp,
      pkg,
      configName: configFilename(projectRoot),
      configPrefix: configName === 'app.json' ? 'expo.' : '',
    };
  } else {
    // get the externally hosted manifest
    return {
      exp: await ThirdParty.getManifest(options.publicUrl, options),
      configName: options.publicUrl,
      configPrefix: '',
      pkg: {},
    };
  }
}

platform?: 'android' | 'ios' | 'all';
    expIds?: Array;
    type?: string;
    releaseChannel?: string;
    bundleIdentifier?: string;
    publicUrl?: string;
  } = {}
) {
  if (!options.publicUrl) {
    // get the manifest from the project directory
    const { exp, pkg } = await readConfigJsonAsync(projectRoot);
    const configName = configFilename(projectRoot);
    return {
      exp,
      pkg,
      configName: configFilename(projectRoot),
      configPrefix: configName === 'app.json' ? 'expo.' : '',
    };
  } else {
    // get the externally hosted manifest
    return {
      exp: await ThirdParty.getManifest(options.publicUrl, options),
      configName: options.publicUrl,
      configPrefix: '',
      pkg: {},
    };
  }
}

export async function getPublishInfoAsync(root: string): Promise {
  const user = await UserManager.ensureLoggedInAsync();

  if (!user) {
    throw new Error('Attempted to login in offline mode. This is a bug.');
  }

  let { username } = user;

  const { exp } = await readConfigJsonAsync(root);

  const name = exp.slug;
  const { version, sdkVersion } = exp;

  const configName = configFilename(root);

  if (!sdkVersion) {
    throw new Error(`sdkVersion is missing from ${configName}`);
  }

  if (!name) {
    // slug is made programmatically for app.json
    throw new Error(`slug field is missing from exp.json.`);
  }

  if (!version) {
    throw new Error(`Can't get version of package.`);
  }

  const remotePackageName = name;
  const remoteUsername = username;