robots-agent

robots.txt agent with cache.

• robots-agent
  • Usage
  • API
  • Errors
  • Difference from robots-parser
  • Implementation

Usage

import {
  createRobotsAgent
} from 'robots-agent';

const robotsAgent = createRobotsAgent();

const firstUsageExample = async () => {
  // The first request retrieves robots.txt contents and initiates an instance of 'robots-parser'.
  const robotsIsAvailable = await robotsAgent.isRobotsAvailable('http://gajus.com/');

  // If robots.txt is not available, then `isAllowed` and other methods will throw an error.
  if (!robotsIsAvailable) {
    return false;
  }
};

const secondUsageExample = async () => {
  // robots.txt cache is per a unique protocol+hostname combination, i.e.
  // 'http://gajus.com/' and 'https://gajus.com/' will result in two robots.txt lookups.
  const robotsIsAvailable = await robotsAgent.isRobotsAvailable('https://gajus.com/');

  if (!robotsIsAvailable) {
    return false;
  }

  // Follow up requests for the same protocol+hostname combination will not create new HTTP requests.
  await robotsAgent.isAllowed('https://gajus.com/foo/');
  await robotsAgent.isAllowed('https://gajus.com/bar/');
};

const main = async () => {
  await firstUsageExample();
  await secondUsageExample();
};

main();

API

/**
 * @property getMatchingLineNumber https://github.com/samclarke/robots-parser#getmatchinglinenumberurl-ua
 * @property getPreferredHost https://github.com/samclarke/robots-parser#getpreferredhost
 * @property getSitemaps https://github.com/samclarke/robots-parser#getsitemaps
 * @property isAllowed https://github.com/samclarke/robots-parser#isallowedurl-ua
 * @property isDisallowed https://github.com/samclarke/robots-parser#isdisallowedurl-ua
 * @property isRobotsAvailable Identifies whether robots.txt is available for the URL.
 */
type RobotsAgentType = {|
  +getMatchingLineNumber: (url: string, userAgent?: string) => Promise<number>,
  +getPreferredHost: (url: string) => Promise<string | null>,
  +getSitemaps: (url: string) => Promise<$ReadOnlyArray<string>>,
  +isAllowed: (url: string, userAgent?: string) => Promise<boolean>,
  +isDisallowed: (url: string, userAgent?: string) => Promise<boolean>,
  +isRobotsAvailable: (url: string, userAgent?: string) => Promise<boolean>
|};

Errors

All robots-agent errors extend from RobotsAgentError.

RobotsNotAvailableError is thrown when any of the robots-parser methods are invoked for a URL with unavailable robots.txt.

import {
  RobotsAgentError,
  RobotsNotAvailableError
} from 'robots-agent';

Difference from robots-parser

robots-agent abstract robots-parser methods by automating retrieval and cache of robots.txt content and safe handling of robots-parser methods.

Unlike robots-parser, robots-agent will throw an error if getMatchingLineNumber, getPreferredHost, getSitemaps, isAllowed or isDisallowed is invoked for a URL that does not have robots.txt. Use isRobotsAvailable to check availability of robots.txt prior to invoking the parser methods.

Implementation

robots-agent uses robots-parser to implement all robots.txt checks.