bail! in render() if specified theme directory does not exist

[clement2026]

This PR fixes #1756.

With the following config,

#book.toml

[output.html]
theme = "./xxx"

if ./xxx directory does not exist, an error message will be logged:

#log

2022-04-25 02:19:12 [INFO] (mdbook::book): Book building has started
2022-04-25 02:19:12 [INFO] (mdbook::book): Running the html backend
2022-04-25 02:19:12 [ERROR] (mdbook::config): theme dir "./xxx" does not exist
2022-04-25 02:19:12 [INFO] (mdbook::cmd::serve): Serving on: http://localhost:3000
2022-04-25 02:19:12 [INFO] (warp::server): Server::run; addr=127.0.0.1:3000
2022-04-25 02:19:12 [INFO] (warp::server): listening on http://127.0.0.1:3000 
2022-04-25 02:19:12 [ERROR] (mdbook::config): theme dir "./xxx" does not exist
2022-04-25 02:19:12 [INFO] (mdbook::cmd::watch): Listening for changes...

[ehuss]

Thanks! I think I would expect mdbook to exit with an nonzero status if there is an error. Maybe instead of adding a check to the theme_dir method, it could just check if it exists in the render method, and bail! if it doesn't exist?

[clement2026]

Thanks! I think I would expect mdbook to exit with an nonzero status if there is an error. Maybe instead of adding a check to the theme_dir method, it could just check if it exists in the render method, and bail! if it doesn't exist?

Yes, this looks much better. I've changed the content of commit.

With the following config,

#book.toml

[output.html]
theme = "./xxx"

if ./xxx directory does not exist, build will fail:

$ mdbook build
2022-04-26 20:33:37 [INFO] (mdbook::book): Book building has started
2022-04-26 20:33:37 [INFO] (mdbook::book): Running the html backend
2022-04-26 20:33:37 [ERROR] (mdbook::utils): Error: Rendering failed
2022-04-26 20:33:37 [ERROR] (mdbook::utils): 	Caused By: theme dir /Users/clark/projects/site/./xxx does not exist

[ehuss]

Thanks, can you add a test for this? (I know it is a bit trivial, but I think it is good to keep test coverage of error cases.)

[clement2026]

Thanks for the reminder! I've added a test function. Since it's my first time to write a test for mdBook, let me know if anything is missing.

[ehuss]

Looks good, thanks!

There is some risk that this will cause some unexpected errors for some projects, but I don't expect that to affect too many people.