Web API dependent HTML validation

[katrinabrock]

Closes #1494

[katrinabrock]

This code is actually working. (CI is just complaining because I didn't add curl as a dependency, but it's already a transitive dependency with xfun.)

I marked it as a draft only because I don't think it should be merged without further discussion. In particular, sourcing a helper from test-rmd.R seems like it's against the spirit of test-rmd.R's simplicity.

[katrinabrock]

@yihui This is fully working from my perspective. I implemented Option 2 form the options described in #1494.

You can see the tests are passing with no changes to the actual bookdown code. To show they're working, I merged the changes in this PR into the branch demoing the silent failure.

One-line diff between that branch and this branch

git diff html-validation silent-breakage-demo 
diff --git a/R/html.R b/R/html.R
index dad883f8..6959364c 100644
--- a/R/html.R
+++ b/R/html.R
@@ -279,7 +279,7 @@ split_chapters = function(
   # Need to take care of the div tags here before restore_part_html and
   # restore_appendix_html erase the section ids of the hidden PART or APPENDIX
   # sections.
-  if (split_level > 1) {
+  if (FALSE) {
     body = x[(i5 + 1):(i6 - 1)]
     h1 = grep('^<div (id="[^"]+" )?class="section level1("| )', body) + i5
     h2 = grep('^<div (id="[^"]+" )?class="section level2("| )', body) + i5

You can see the CI job is now failing with

 Error in eval(quote({ : 
  HTML issues detected in section-1.html, section-1.html, section-2.html, section-2.html, section-3.html, section-3.html, sub2.html, sub2.html, sub2.html, sub2.html, subsection-1.html, subsection-1.html, subsection-1.html, subsection-1.html, subsection-3.html, subsection-3.html, subsection-3.html, subsection-3.html, subsection-footnotes-2.html, subsection-footnotes-2.html, subsection-footnotes-2.html, subsection-footnotes-2.html, test-footnote.html, test-footnote.html
Calls: local -> eval.parent -> eval -> eval -> eval -> eval
Execution halted

except for the Mac and Windows jobs on which I skip this test as they don't have docker installed.

The passing of mac and windows jobs demonstrates that with no API and W3C_MARKUP_VALIDATOR_BASEURL unset, the tests pass without running the HTML validation so this will be opt-in for bookdown developer's local workflow. It will not impact end users at all because bookdown code itself isn't changing, only tests and CI.

[yihui]

This is amazing. Thank you!

[katrinabrock]

Glad you like it!

btw - here is what the errors look like with the status quo code when you don't make any exceptions:

Error in eval(quote({ : 13 HTML issues detected:
  custom-environments.html: CSS: “border-top”: “solid\9” is not a “color” value.
  custom-environments.html: CSS: “border-bottom”: “solid\9” is not a “color” value.
  custom-environments.html: Attribute “number” not allowed on element “div” at this point.
  section-1.html: Attribute “number” not allowed on element “div” at this point.
  section-2.html: Attribute “number” not allowed on element “div” at this point.
  section-3.html: Attribute “number” not allowed on element “div” at this point.
  sub2.html: Attribute “number” not allowed on element “div” at this point.
  subsection-1.html: Attribute “number” not allowed on element “div” at this point.
  subsection-22.html: Attribute “number” not allowed on element “div” at this point.
  subsection-3.html: Attribute “number” not allowed on element “div” at this point.
  subsection-footnotes-1.html: Attribute “number

Probably easy enough to resolve. Might make a good first issue for someone.