Say goodbye broken links on your static sites. Platform independent, fast, and built in python.
Recently, fastai has been hard at work improving and overhauling nbdev, a literate programming environment for python. A key feature of nbdev is automated generation of documentation from Jupyter notebooks. This documentation system adds many niceties, such as the following types of hyperlinks automatically:
Because documentation is so easy to create and maintain in nbdev, we find ourselves and others creating much more of it! In addition to automatic hyperlinks, we often include our own links to relevant websites, blogs and videos when documenting code. For example, one of the largest nbdev generated sites, docs.fast.ai, has more than 300 external and internal links at the time of this writing.
Due to the continued popularity of fastai and the growth of new nbdev projects, grooming these links manually became quite tedious. We investigated solutions that could verify links for us automatically, but were not satisfied with any existing solutions. These are the features we desired:
https://docs.fast.ai/tutorial
should not result in a web request, but rather introspection of the local file system for the presence of tutorial.html
in the right location.We tried tools such as linkchecker and pylinkvalidator, but these required your site to be first be hosted. Since we wanted to check links on a static site, hosting is overhead we wanted to avoid.
This is what led us to create fastlinkcheck, which we discuss below.
Note: For Ruby users, htmlproofer apperas to provide overlapping functionality. We have not tried this library.
For this tour we will be referring to the files in the fastlinkcheck repo. You should clone this repo in the current directory in order to follow along:
git clone https://github.com/fastai/fastlinkcheck.git
cd fastlinkcheck
Cloning into 'fastlinkcheck'... remote: Enumerating objects: 135, done. remote: Counting objects: 100% (135/135), done. remote: Compressing objects: 100% (98/98), done. remote: Total 608 (delta 69), reused 76 (delta 34), pack-reused 473 Receiving objects: 100% (608/608), 1.12 MiB | 10.47 MiB/s, done. Resolving deltas: 100% (302/302), done.
You can install fastlinkcheck
with pip:
pip install fastlinkcheck
After installing fastlinkcheck
, the cli command link_check
is available from the command line. We can see various options with the --help
flag.
link_check --help
usage: link_check [-h] [--host HOST] [--config_file CONFIG_FILE] [--pdb] [--xtra XTRA] path Check for broken links recursively in `path`. positional arguments: path Root directory searched recursively for HTML files optional arguments: -h, --help show this help message and exit --host HOST Host and path (without protocol) of web server --config_file CONFIG_FILE Location of file with urls to ignore --pdb Run in pdb debugger (default: False) --xtra XTRA Parse for additional args (default: '')
From the root of fastlinkcheck repo, We can search the directory _example/broken_links
recursively for broken links like this:
link_check _example/broken_links
ERROR: The Following Broken Links or Paths were found: - 'http://fastlinkcheck.com/test.html' was found in the following pages: - `/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.html` - 'http://somecdn.com/doesntexist.html' was found in the following pages: - `/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.html` - Path('/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.js') was found in the following pages: - `/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.html`
Specifying the --host
parameter allows you detect links that are internal by identifying links with that host name. External links are verified by making a request to the appropriate website. On the other hand, internal links are verified by inspecting the presence and content of local files.
We must be careful when using the --host
argument to only pass the host (and path, if necessary) without the protocol. For example, this is how we specify the hostname if your site's url is http://fastlinkcheck.com/test.html
:
link_check _example/broken_links --host fastlinkcheck.com
ERROR: The Following Broken Links or Paths were found: - 'http://somecdn.com/doesntexist.html' was found in the following pages: - `/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.html` - Path('/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.js') was found in the following pages: - `/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.html`
We now have one less broken link as there is indeed a file named test.html
in the root of the path we are searching. However, if we add a path to the end of --host
, such as fastlinkcheck.com/mysite
the link would again be listed as broken because _example/broken_links/mysite/test.html
does not exist:
link_check _example/broken_links --host fastlinkcheck.com/mysite
ERROR: The Following Broken Links or Paths were found: - 'http://fastlinkcheck.com/test.html' was found in the following pages: - `/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.html` - 'http://somecdn.com/doesntexist.html' was found in the following pages: - `/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.html` - Path('/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.js') was found in the following pages: - `/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.html`
You can ignore links by creating a text file that contains a list of urls and paths to ignore. For example, the file _example/broken_links/linkcheck.rc
contains:
cat _example/broken_links/linkcheck.rc
test.js https://www.google.com
We can use this file to ignore urls and paths with the --config_file
argument. This will filter out references to the broken link /test.js
from our earlier results:
link_check _example/broken_links --host fastlinkcheck.com --config_file _example/broken_links/linkcheck.rc
ERROR: The Following Broken Links or Paths were found: - 'http://somecdn.com/doesntexist.html' was found in the following pages: - `/Users/hamelsmu/github/fastlinkcheck/_example/broken_links/test.html`
Finally, if there are no broken links, link_check
will not return anything. The directory _example/no_broken_links/
does not contain any HTML files with broken links:
link_check _example/no_broken_links
No broken links found!
You can also use these utilities from python instead of the terminal. Please see these docs for more information.
link_check
in GitHub Actions¶The link_check
CLI utility that is installed with fastlinkcheck
can be very useful in continuous integration systems like GitHub Actions. Here is an example GitHub Actions workflow that uses link_check
:
name: Check Links
on: [workflow_dispatch, push]
jobs:
check-links:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- uses: actions/setup-python@v2
- name: check for broken links
run: |
pip install fastlinkcheck
link_check _example
We can a few more lines of code to open an issue instead when a broken link is found, using the gh cli:
...
- name: check for broken links
run: |
pip install fastlinkcheck
link_check _example 2> err || true
export GITHUB_TOKEN="YOUR_TOKEN"
[[ -s err ]] && gh issue create -t "Broken links found" -b "$(< err)" -R "yourusername/yourrepo"
We can extend this even further to only open an issue when another issue with a specific label isn't already open:
...
- name: check for broken links
run: |
pip install fastlinkcheck
link_check "docs/_site" --host "docs.fast.ai" 2> err || true
export GITHUB_TOKEN="YOUR_TOKEN"
if [[ -z $(gh issue list -l "broken-link")) && (-s err) ]]; then
gh issue create -t "Broken links found" -b "$(< err)" -l "broken-link" -R "yourusername/yourrepo"
fi
See the GitHub Actions docs for more information.
The following resources are relevant for those interested in learning more about fastlinkcheck
: