When linking to other markdown files, in particular to the default README.md, it may be preferable (most of the time?) to reference them by their permalink, instead of the actual location in the directory structure. Because, if the default README.md ever changes, then the link will work; however, the content isn't exactly what it should be, so to guard against that, you want to be explicit as you can in your links.

For example, this is fine, as long as the content in /path/to/some/README.md doesn't change.

Go read the [usage docs](/path/to/some/README.md)

But, to safe guard against accidentally pointing someone to the wrong docs, it's preferred to instead to do this:

Go read the [usage docs](/path/to/some/usage-docs)

and, in the /path/to/some/README.md file, provide a permalink...

---
permalink: /path/to/some/usage-docs.html
---

This is the `/path/to/some/README.md` file, containing content for the usage docs.

But, check-md doesn't appear to account for this, and returns a dead link, even though the link isn't really dead because the permalink properly places the README.md at the permalink location.

File is not found: [usage docs](/path/to/some/usage-docs) (/Users/CDura/code/my-project/src/another/page/README.md:32:99)

For example, when using webpack aliases (as suggested by vuepress docs), we have URLs for images that look like this:

![image alt](~@assets/my-image.png)

There is currently no way to declare this alias.

When cross-linking to "external" websites, the website you're linking to may be extremely slow in returning a response. This results in some false failures being reported.

It would be good to allow for a max timeout or delay before reporting that the link is "dead".

An example site that I link to that always reports as "dead":

https://www.tobiidynavox.com/en-us/support-training/windows-control-2/

Vuepress has updated its slugify function (for both v1 and next/v2):

const rControl = /[\u0000-\u001f]/g
const rSpecial = /[\s~`!@#$%^&*()\-_+=[\]{}|\\;:"'“”‘’–—<>,.?/]+/g
const rCombining = /[\u0300-\u036F]/g

export const slugify = (str: string): string =>
  str
    .normalize('NFKD')
    // Remove accents
    .replace(rCombining, '')
    // Remove control characters
    .replace(rControl, '')
    // Replace special characters
    .replace(rSpecial, '-')
    // Remove continuos separators
    .replace(/-{2,}/g, '-')
    // Remove prefixing and trailing separators
    .replace(/^-+|-+$/g, '')
    // ensure it doesn't start with a number (#121)
    .replace(/^(\d)/, '_$1')
    // lowercase
    .toLowerCase()

It adds steps of normalizing and removing accents, and no longer requires diacritics dependency. Also, rSpecial adds some new characters.

It's time to fix it now, but should we change defaultSlugify function directly or add a new function / config for vuepress preset?

I have added a sizing to my svg link and it generated a dead link error.

1 dead links was found

  File is not found: ![document structure](/document_structure.svg =573x400) (/documentation/guides/main_concepts/documents.md:6:1)

This is how the link is transformed:

'/document_structure.svg%20=573x400',

Should we pattern match % and remove what is behind ?

Strict Extension Mode

The strict extension mode makes the .md extension mandatory in links to recognized md files.

This means that a link to a markdown file not containing the .md extension will raise a warning:

This only raises an error when the .md extension is missing on a md file. If the link is to a directory because it will automatically redirect to the README.md or index.md file inside that directory, it will NOT raise a warning.

Since dir is a directory containing a README.md file, this will NOT raise an error:

[test17](/dir)
[test18](/dir#test)

Since other is a markdown file whose .md extension is missing, this will raise an error:

[test7](/other#ctx-get-name)

[test8](/other#cccc)

Checking markdown...

2 warning was found
 
File found with this name but .md extension missing: [test7](/other#ctx-get-name) (/Users/charlottevermandel/check-md/test/fixtures/docs1/test.md:17:1)
File found with this name but .md extension missing: [test8](/other#cccc) (/Users/charlottevermandel/check-md/test/fixtures/docs1/test.md:19:1)

Usage

it is used, as --fix, by adding the option without parameter.

check-md -p 'vuepress' -c 'test/fixtures/vuepress' --strict-ext

Implementation

I'm working on it on this PR: bidoubiwa#1. I will make a PR here once it's done.

It would be nice to be able to pass in a format that would print all of the errors as GitHub Actions annotations.

Step to reproduce

When the markdown file contains typescript like:

- Type: `{ [path: string]: Object }`

We'll get following error:

File is not found: [path: string]: Object }` (/path/to/foo.md:86:12)

There's some legit reasons that you may want to have a link that actually doesn't go anywhere in the markdown, like [example link text](#), especially in documentation sites.

In fact, you may want to be able to ignore any particular pattern in the link URL (not just ignore a particular filename pattern). For example:

Here's a [internal link](https://auth.my-project.com) that is behind Oauth, so it'll always look ☠️, but it's not 💀