markdown link checker sc

ALPHA - Mostly just attempting better handling of internal links.
Probably never coming out of alpha. Bit of fun.

Markdown link checker in node.
Better handling of internal link checking.

Current version only does internal link checking

``
Usage: markdown_link_checker_sc [options]

Options:
-r, --repo Repo root directory. Defaults to current directory. Everything resolved relative to this.) (default: "")
-d, --doc [directory] Docs root directory, relative to -r (such as docs). Defaults to '' (all docs in root of repo). Use -d as well to restrict
search to a particular subfolder. Defaults to current directory. (default:
"D:\\github\\hamishwillee\\markdown_link_checker_sc")
-e, --subdir [directory] A subfolder of the docs root (-d) to search for markdown and html files. Such as: en for an English subfolder. Default
empty (same as -d directory) (default: "")
-i, --imagedir [directory] The directory to search for all image files for global orphan checking, relative docs root (-d) - such as: assets or en.
Default empty if not explicitly set, and global orphan checking will not be done (default: "")
-c, --headingAnchorSlugify [value] Slugify approach for turning markdown headings into heading anchors. Currently support vuepress only and always (default:
"vuepress")
-h, --tryMarkdownforHTML [value] Try a markdown file extension check if a link to HTML fails. (default: true)
-l, --log Types of console logs to display logs for debugging. Types: functions, todo etc.
-f, --files JSON file with array of files to report on (default is all files). JSON paths are usually relative to git repo root -r.
(default: "")
-t, --toc [value] full filename of TOC/Summary file in file system. If not specified, inferred from file with most links to other files
-u, --site_url [value] Site base url in form dev.example.com (used to catch absolute urls to local files)
-o, --logtofile [value] Output logs to file (default: true)
-p, --interactive [value] Interactively add errors to the ignore list at /_link_checker_sc/ignore_errors.json (default: false)
-c, --anchor_in_heading [value] Detect anchors in heading such as: # Heading {#anchor} (default: true)
-x, --externallink [value] Output logs to file (default: false)
-e, --errors [values] WIP (don't use) Error type names to remove, space separated. By default ExternalLinkWarning (default: "ExternalLinkWarning")
--help display help for command
`

Ignore file

You can create a _link_checker_sc\ignorefile.json in the docs (path specified by -d) that lists any files you want to avoid parsing.
This is a JSON array of file paths relative the the docsroot.

For example, to not parse en/_sidebar.md your ignore file would have this pattern:

`
["en/_sidebar.md"]
`

Note that a missing ignorefile is not an error.

What link formats can it match

Currently matches:
- \Link text, \Link text, \Link text
- Link text
- !Image alt
- some text
-
-
- [reference link text][reference name], where the reference is define as [reference name]: reference_url "reference title"
- Only supports reference name and text format - not "plain reference name" like [reference name]
- reference must be all on one line, and can have up to three whitespaces before it on line. May not have text after reference title.


> Note: It uses simple regexp. If you have a link commented out, or inside a code block that may well be captured.

There are heaps of link formats it does not match:

- - doesn't support autolinks
- www.fred.com - Doesn't support auto-links external.
- - Doesn't properly support a link around an image.
- Reference links where the reference is defined across lines.


Essentially lots of the other things https://github.github.com/gfm/

The regex that drives this is very simple.

There are many other alternatives, such as: https://github.com/tcort/markdown-link-check
You might also use a tokenziker or round trip to HTML using something like https://marked.js.org/using_advanced#inline in future as HTML is eaiser to extract links from.

This does catch a LOT of cases though, and is pretty quick.

Also does

- Catches markdown files that are orphans - i.e. not linked by any file, or not linked by file which has the most links (normally the TOC file)
- Catches orphan images
- Allows you to specify that some errors are OK to ignore. These are stored in a file. See -i` options\
- Can run its own external link checker if -x is True. This is quite useful as you can control what errors get reported.

TODO

Anchors that are not URL-escaped can trip it up.
- You can URL escape them like this: Airframe Reference
- BUT the comparison of the anchor is NOT url escaped, so you would need to convert back to compare.
- URL escaping anchors and reversing for comparison is not done.

Anchors defined in id in a or span are caught. Need to check those in video, div are also caught and used in internal link checking.

Get images in/around the source files that are not linked - i.e. orphan images.

How does it work?

The way this works:
- Specify the directory and it will search below that for all markdown/html files.
- It loads each file, and:
- parses for markdown and html style links for both page and image links.
- parses headings and builds list of anchors in the page (as per vuepress) for those headings (poorly tested code)
- parses for html elements with ids, that are also link targets.
- Then it parses the results, comparing internal links to internal anchors to see if it can find matching files, and matching headings or anchors within files.
- If it can't match, that is an error - which gets added to the list of errors with a type and enough detail to handle.
- Errors are then filtered based on:
- pages in a json file defined using -f (and possibly -r).
- Finally the output is exported in a markdown friendly output format.

Lots more to do, but this already catches lots of internal errors.