Enhancement: support for non-standard RMarkdown directory structures.

[jonathan-g]

I have the same issue as was raised in #146 (and I originally posted this issue as a comment there).

I organize my reveal.js slides for a semester in a directory structure:

semester:
    lecture_lib (common material: css, js, etc.)
        assets (custom css themes, custom js, images, etc. that are shared across the whole project)
        revealjs
        font-awesome
    slides
        class_01
            assets (per-class assets)
                images (images to include)
                videos (video files)
                fig (figures generated by RMarkdown)
        class_02
            assets (per-class assets)
                images (images to include)
                videos (video files)
                fig (figures generated by RMarkdown)
        c;lass_03
            assets (per-class assets)
                images (images to include)
                videos (video files)
                fig (figures generated by RMarkdown)
        ...

This lets me keep a consistent structure for each lecture.

If I use pandoc 2.7.x, RMarkdown works fine with my directory structures, but if I use any later version of Pandoc rendering the .Rmd file fails with an error message about relativeTo() because lib_dir is not a descendant of output_dir.

This is not a bug per-se since by design, RMarkdown does not support this kind of directory structure. But it is something that a number of people have expressed interest in (#146, #472, https://github.com/jayhesselberth/widgetdown/issues/4, workflowr/workflowr#95).

My non-standard (and unsupported) directory structure worked for many years, using a custom reveal.js HTML template for Pandoc to handle a more flexible directory structure but it broke several months ago when Pandoc moved to version 2.9 and rmarkdown introduced html_dependency_header_attrs to fix the duplication of HTML class attributes from <section> to <h[1-9]> tags that Pandoc introduced with version 2.8 or 2.9. I was able to work around this by continuing to work with an older Pandoc version (2.7).

I raise this in part because I think I could address this with a relatively minor PR (I have this working on a fork of rmarkdown at https://github.com/jonathan-g/rmarkdown/tree/minimal-tree-fix, and it changes about 14 lines of code, all of which are in the html_dependencies_as_string() function). I need to test this patch more before submitting it as a PR, but it should allow this non-standard directory structure through the YAML lib_dir parameter without disturbing any use cases except where lib_dir begins with ...

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[yihui]

If the change required is relatively simple, please feel free to submit a PR. I'd love to support the directory structure that you mentioned. Thank you!

[jonathan-g]

What I have now is 96 new lines of code in html_dependencies.R comprising

• one contiguous block of about 86 LOC providing two new internal (i.e., not exported) functions
• and 10 new lines of code in the function html_dependencies_as_string().

[cderv]

I think you can submit the PR @jonathan-g !

[jdfoote]

Any update on this?

I am making revealjs slides for a class, and it seems like it makes sense to just refer to the revealjs library rather than to include it in every subdirectory. I thought that was a common use case for the lib_dir command?

Is there a better approach?

[jonathan-g]

Sorry for the delay. I have been holding off because I wanted to test my patch to make sure it doesn't break anything, but I should be able to submit a PR soon. In the meantime, if you want to look at my work, my fork is at https://github.com/jonathan-g/rmarkdown and the patch for the new directory tree structure can be found in the branches https://github.com/jonathan-g/rmarkdown/tree/jg-devel and https://github.com/jonathan-g/rmarkdown/tree/minimal-tree-fix (this last one is prunding my changes down to a minimal patch to keep the PR small).

I've been using the modified version of rmarkdown in the jg-devel branch for the past year with no problems but I'm super cautious about making a PR to such a widely used package and want to take the time to be sure that there aren't unintended breaking changes for other people's use cases.

[jonathan-g]

I have submitted PR #2199 to implement this enhancement.