folyd / robotstxt

A native Rust port of Google's robots.txt parser and matcher C++ library.

robotstxt

A native Rust port of Google's robots.txt parser and matcher C++ library.

• Native Rust port, no third-part crate dependency
• Zero unsafe code
• Preserves all behavior of original library
• Consistent API with the original library
• 100% google original test passed

Installation

[dependencies]
robotstxt = "0.3.0"

Quick start

use robotstxt::DefaultMatcher;

let mut matcher = DefaultMatcher::default();
let robots_body = "user-agent: FooBot\n\
                   disallow: /\n";
assert_eq!(false, matcher.one_agent_allowed_by_robots(robots_body, "FooBot", "https://foo.com/"));

About

Quoting the README from Google's robots.txt parser and matcher repo:

The Robots Exclusion Protocol (REP) is a standard that enables website owners to control which URLs may be accessed by automated clients (i.e. crawlers) through a simple text file with a specific syntax. It's one of the basic building blocks of the internet as we know it and what allows search engines to operate.

Because the REP was only a de-facto standard for the past 25 years, different implementers implement parsing of robots.txt slightly differently, leading to confusion. This project aims to fix that by releasing the parser that Google uses.

The library is slightly modified (i.e. some internal headers and equivalent symbols) production code used by Googlebot, Google's crawler, to determine which URLs it may access based on rules provided by webmasters in robots.txt files. The library is released open-source to help developers build tools that better reflect Google's robots.txt parsing and matching.

Crate robotstxt aims to be a faithful conversion, from C++ to Rust, of Google's robots.txt parser and matcher.

Testing

$ git clone https://github.com/Folyd/robotstxt
Cloning into 'robotstxt'...
$ cd robotstxt/tests 
...
$ mkdir c-build && cd c-build
...
$ cmake ..
...
$ make
...
$ make test
Running tests...
Test project ~/robotstxt/tests/c-build
    Start 1: robots-test
1/1 Test #1: robots-test ......................   Passed    0.33 sec

License

The robotstxt parser and matcher Rust library is licensed under the terms of the Apache license. See LICENSE for more information.

robotstxt's Issues

Why does allowed_by_robots and one_agent_allowed_by_robots parse robotstxt for each request?

This API and example are really confusing...
Why cannot we simply parse once and then call methods to check if URL is allowed?...

Panics when slicing within char boundaries

The parser can panic if it tries to slice a string within char boundaries.

thread '<unnamed>' panicked at 'byte index 58198 is not a char boundary; it is inside '\u{a0}'
...
/root/.cargo/registry/src/github.com-1ecc6299db9ec823/robotstxt-0.3.0/src/parser.rs:169:57

crashes for deviantart robots.txt

When parsing https://www.deviantart.com/robots.txt

User-agent: *
Disallow: /*q=
Disallow: /users/*?
Disallow: /join/*?
Disallow: /morelikethis/
Disallow: /download/
Disallow: /checkout/
Disallow: /global/
Disallow: /api/
Disallow: /critiques/
 
Sitemap: http://sitemaps.deviantart.net/sitemap-index.xml.gz

the parser fails with

thread 'main' panicked at 'assertion failed: !val.is_empty()', /home/me/.local/share/cargo/registry/src/github.com-1ecc6299db9ec823/robotstxt-0.2.0/src/parser.rs:207:17

Reproduction:

use robotstxt::DefaultMatcher;

fn main() {
    let robots_content = r#"User-agent: *
Disallow: /*q=
Disallow: /users/*?
Disallow: /join/*?
Disallow: /morelikethis/
Disallow: /download/
Disallow: /checkout/
Disallow: /global/
Disallow: /api/
Disallow: /critiques/
 
Sitemap: http://sitemaps.deviantart.net/sitemap-index.xml.gz"#;
    let mut matcher = DefaultMatcher::default();
    matcher.one_agent_allowed_by_robots(&robots_content, "oldnews", "https://www.deviantart.com/");
}

I'm assuming it is because of the line between the Disallows and the Sitemap, which only contains a single space.

Document test dependencies

While following README.md and trying to build && run official google tests
I get this error
/usr/bin/ld: cannot find -labsl::container collect2: error: ld returned 1 exit status

on make stage

What should I install in order to fix this and run tests?

uname -a
5.8.0-53-generic #60-Ubuntu SMP Thu May 6 07:46:32 UTC 2021 x86_64 x86_64 x86_64 GNU/Linux

panics when robots_txt is not valid

Fetching https://install.pivpn.io/robots.txt redirects to https://raw.githubusercontent.com/pivpn/pivpn/master/auto_install/install.sh which is a text/plain shell script.

The parser panics when trying to parse that file.

thread 'main' panicked at 'assertion failed: self.type_ == ParseKeyType::Unknown && !self.key_text.is_empty()', /home/me/.local/share/cargo/git/checkouts/robotstxt-269483cb38f6894f/ffe972d/src/parser.rs:88:9

I'm not entirely sure what the correct behavior should be, but simply ignoring unparsable lines seems like a good option.