Rendering failed when book directory contains broken symlink

[soareschen]

When the book src directory contains broken symlink, mdbook will fail to build the book with obscure error message No such file or directory.

Steps to reproduce:

• Create a broken symlink in the book src directory, e.g. ln -s /path/not-found.

• Running mdbook will produce the following error:

$ mdbook build
[INFO] (mdbook::book): Book building has started
[INFO] (mdbook::book): Running the html backend
[ERROR] (mdbook::utils): Error: Rendering failed
[ERROR] (mdbook::utils):    Caused By: No such file or directory (os error 2)

As shown above, the error message does not give any clue that the error is caused by broken symlink, making it difficult to debug.

Tested with mdbook v0.4.4 on Linux.

[maowen]

With the current implementation on the master branch, mdBook still fails to build when the book directory contains a broken symlink although there is now a helpful error message that provides helpful feedback and makes it more clear that the broken symlink caused the build to fail.

I recently submitted an MR (#1944) that I believe provides a full resolution to the original issue. Would it make sense to re-open this issue or should I create a new one instead?