clean_site default to preview = TRUE

[cderv]

This will close #1971

• preview = TRUE by default now - this will affect the behavior of Clean All button in website project Build pane
• A message is output to console to inform about the file that could be removed.
• clean_site(preview = FALSE) will effectively remove those files
• Nothing is done if no file returned by the generator clean function
• if quiet = FALSE and preview = FALSE, a message is also output to console - useful for knowing what happens in the Build pane

I also

• refactored tests and add some for better coverage.
  • Added withr as Suggests because it is really useful for clean test helper.
• adapted mark_dirs from bookdown - will do a PR in xfun

One question remaining:

• Should clean_site() check for existence of the files and directories mentioned in message ?
• Or should the generator$clean() function only return filepath that exists ?

I think the latter would be best but currently it does not - for example blogdown:

==> rmarkdown::clean_site()

These files and folders can probably be removed:

* blogdown
* public/
* content/_index.markdown
* content/post/2015-07-23-r-rmarkdown/index.html
* static/rmarkdown-libs

Use `rmarkdown::clean_site(preview = FALSE)` to remove them.

blogdown folder does not exist, static/rmarkdown-libs neither (because page bundle I think). I find it puzzling that it is output in the message

What do you think ?

[cderv]

Also I have opened #1974 for the idea we shared last Friday.

If you find it interesting and good enough in its implementation, we could ship it with this. Otherwise, we have time to think about it.

[cderv]

Would it be interesting to have an option for preview to change the default behavior of the IDE button to FALSE ?

Not so sure, so I did not add it

[yihui]

Yes, that could be useful (e.g., preview = getOption('rmarkdown.clean_site.preview', TRUE)), but let's wait until someone asks for it.

[cderv]

Oh I remember this method of yours now - not used to that: get ideas but wait for people asking ! 😄

[yihui]

You can definitely also proactively ask if anyone wants this feature in advance. I just don't have the energy to do this myself :)

[yihui]

• Should clean_site() check for existence of the files and directories mentioned in message ?
• Or should the generator$clean() function only return filepath that exists ?

I'd prefer the latter. I'll fix the problem in blogdown. Thanks!

[yihui]

Yes, that could be useful (e.g., preview = getOption('rmarkdown.clean_site.preview', TRUE)), but let's wait until someone asks for it.