Seems like a good idea to me. We already display warnings for broken links to '.md' files. Looking at how that works would probably be a good start.

This could be a little tricky as Markdown files are checked against the Nav (a previously compiled list of pages), not against the file system. And in that part of the code we don't have access to the doc_dir or the site_dir so we only have the relative path with no way to make it absolute and therefore no way to check it against the file system. For that matter, we don't even have access to the location of the current file, so there is no way to know what the path is relative to (i.e., ../../some/path/).

In the end, I expect this to be more difficult that one would think. This will likely also be a problem if/when support for "hidden" pages is added (see #699). Those pages will be explicitly absent from the Nav and should not generate a warning, but with no way to determine that within the Markdown Extension, there is no way to conditionally not raise the warning.

I see two possibilities to that problem (which would also directly affect this issue):

1. Remove all related warnings about missing files, which would make any fix here moot.
2. Refactor the relevant code to address all of the issues above, which would make both this and hidden files possible.

The problem stems in part from the fact that Python-Markdown does not really support passing data to an extension to modify its behavior on a file-by-file basis. The idea is that you create a Markdown instance with a config, and that instance is used (without changing behavior) for multiple files. Of course, MkDocs gets around this by creating a new instance for each page, but the API wasn't really designed with this use-case in mind.

Hey there,
Thanks for your pointers. It doesn't sound trivial but I'll take a look and let you know how I get on...

How can I ignore this? I put the images somewhere not in the same repo, then got lots of warning.

@zhangzq warnings are only issued for relative paths. If your images are in a different repo, then they are not within the MkDocs site and should be absolute paths, which would avoid the warnings.

@waylan thanks. I'll change them to absolute paths.

@waylan I found the absolute paths must contains the whole domain part, i.e. http://domain.com/path/file.pdf 。

However, I used different domains in internal and public deploys.

Can I use [link](/path/file.pdf) for link without warning?

Can I use [link](/path/file.pdf) for link without warning?

Yes, that should work fine. If it does not, please open a new issue.

@waylan I opened a new issue at #1621 .