SIGSEGV on long line

[s4n-cz]

Hello,

I have noticed that providing long line of text (around 21 000 characters) crashes the build.

Steps to reproduce

1. Paste a long line of text into the source Markdown file (generate e.g. with Python 'a' * 21000)
2. run mdbook build

   mdbook build
   2022-01-29 16:20:21 [INFO] (mdbook::book): Book building has started
   2022-01-29 16:20:21 [INFO] (mdbook::book): Running the html backend
   
   thread 'main' has overflowed its stack
   fatal runtime error: stack overflow
   zsh: IOT instruction (core dumped)  mdbook build
   

Backtrace from rust-gdb

backtrace.txt

[mattheww]

Note you need a very long single word to cause this problem; just having a long line won't trigger it.

The crash is caused by the search indexing code trying to create a very deeply nested JSON file (it has a nested object for each letter in the word).

I've filed mattico/elasticlunr-rs#44 about this.