Check for the index.html file before trying to opener::open it

[joshrotenberg]

Add a function to find the first displayable chapter, and use it when attempting to open the browser in the build, watch and serve command line commands.

Fixes #1713.

[ehuss]

I think an error would be fine, but if you want to try opening the first non-draft chapter, I think something like the following could work:

if let Some(first) = book.iter().filter_map(|item| match item {
    BookItem::Chapter(Chapter{path: Some(path), ..}) => Some(path),
    _ => None
}).next() {
    let path = book.build_dir_for("html").join(first).with_extension("html");
    dbg!(path);
}

Just keep in mind that the open option is used in multiple commands (build, serve, watch).

[ehuss]

Just checking in to see if you are still interested in completing this?

[joshrotenberg]

Sorry, it fell off my list. I'll pick it back up this week.

[ehuss]

Thanks!