Allow option flags to accept False value

[ojob]

Context

I have a project where pandoc is used to generate a Reveal.JS presentation, and this project aims to be a presentation generator.

In order to allow for offline usage and proper archival, I use the --embed-resources --standalone option flags, and I want this to be the default behavior so I set them in the defaults parameters file.

Observed Problem

During writing, it is much faster not to embedd the resources. But my defaults file activates the --embed-resources, and there is no way to overload the flag for deactivation. Providing --embed-resources=false is refused.

For the moment, I therefore deactivated the embed-resources in the defaults file, but shall take care to activate it in the rendering pipeline.

Proposal

Allow for overloading the embed-resources option from defaults with a command-line value requesting no embedding.

In #8362, in particular with one answer, there is a proposal to extend accepted values for --embed-resources flag with none value: this would be perfect.

[tarleb]

This would require small changes in file src/Text/Pandoc/App/CommandLineOptions.hs, changing NoArg to OptArg for the relevant options.

[ojob]

Thanks for the analysis!

I could see to propose a PR, but I'm not at ease with Haskell; do I need to set up a Haskell environment for this update? Or is a simple file update, and the CI will do its job properly?

[tarleb]

I'd suggest to setup a local Haskell env to enable proper testing. It might be possible to do this only with the CI, but I'd expect it to be a slightly frustrating experience.

ghcup is probably the easiest method to get a Haskell environment up and running. I feel obliged to point out that it is a non-negligible time investment to get started. Compiling pandoc and all of its dependencies from scratch takes ~30 min (less on newer hardware). I think it has become a bit of a meme in Haskell circles.

[samahri]

Hello everyone,
I'm a huge fan of pandoc and appreciate all the great work you do here.

I've taken the initiative to create a pull request that addresses OP's request. Please feel free to take a look at it.

[ojob]

Hi @samahri thanks for the implementation!! My Haskell level would have been really too low to achieve your improvements.

Now I'm looking forward to the release to production :)

[samahri]

Glad I could help!