(sent to Charles direcly by mistake. Charles, this resend gave me the chance to modify my response)
On Mon, Dec 12, 2016 at 10:52 PM, Charles C. Berry <ccberry@ucsd.edu> wrote:
On Mon, 12 Dec 2016, Matt Price wrote:

On Mon, Dec 12, 2016 at 12:16 PM, Charles C. Berry <ccberry@ucsd.edu> wrote:

On Mon, 12 Dec 2016, Matt Price wrote:


[snip]


My questions are:
1. can I pass this html attribute to the <pre><code> block somehow?


Yes.

ATTR_HTML doesn't seem to work.  Is this a bug? If so, should I try to fix
it?


No and no.

Did you try

: (plist-get (cadr src-block) :attr_html)

in `org-html-src-block' ?


ah, ok.  Now I will reveal some of the depths of my ignorance.  Looks like
:attr_html is a plist (right?).

 No, it is a property name. (cadr src-block) is the plist.

:-)  I think what I meant was, looks like (org-export-read-attribute :attr_html src-block) RETURNS a plist.  But that doesn't seem to be quite true, if I'm understanding properly what a plist is. 

Instead it returns a list of this form:
(:code_attribs data-external-libs="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.js" data-other="other" :class some class list)

 Access to the :properties only seems reliable through (org-export-read-attribute :attr_html src_plock :propname), which returns what should be an odd list of symbols (?) as a string. Again, it seems somewhat mysterious to me.

UPDATE: despite the tentative solution seen below, I guess maybe the #+ATTR_XXX attributes are not intended for iteration as I describe, but instead each such attribute should have a well-specified function that the exporter knows about.  If I'm adding attributes -- and it turns out that ox-reveal can interpret a :code_attribs attribute that I hadn't known about -- then I feel like I should structure them in an expected way.  I haven't found documentation about the best practice here and would definitely appreciate further pointers.


See (info "(elisp) Property Lists")


(a) what is the appropriate way to identify an attribute here.  should I
write, e.g.:

#+ATTR_HTML: :data-external-libs "http://underscorejs.org/underscore-min.js"
:class "list of classes"

 Any could be made to work, but I'd use (a). Then

: (org-babel-parse-header-arguments
:  (car (plist-get (cadr src-block) :attr_html)))

will give you

: ((:data-external-libs . "http://underscorejs.org/underscore-min.js") :   (:class . "list of classes"))

ah, ok, thank you.   Someday I hope I really understand list objects and how to transform them.  I think part of the problem is that, unlike in some other languages, programming effectively requires a proper understanding of *what the objects are that you're manipulating*, and I'm just a bit too stupid to learn this effectively on my own. 

And then, if I want to transform this into:
 

data-external-libs="http://underscorejs.org/underscore-min.js" class="list
of classes"

can I just do something like:
(let ((attributes (org-export-get-attribute :attr_html src-block))
 (cl-loop for (key value) in attributes
   (collect (concat key "=" "\"" value "\" " ))))

or do I need to transform the key into a string first?

 Well, I'd just try it and see.
:-) Seems like I should be able to manage this now!


I'm sorry to be writing such basic lisp questions; obviously I need to read
a really good lisp introduction, but I haven't found one yet.


 This is what I use:

* Elisp: (elisp).               The Emacs Lisp Reference Manual.
* Emacs Lisp Intro: (eintr).    A simple introduction to Emacs Lisp programming.

and ample Googling, usually leading to StackOverflow, to get hints on stuff I am fuzzy on. And I read docstrings over and over and ...

This is the method i'm using, but for me it's veeeeerrrrry slow. 

 

Best,

Chuck

Thank you Chuck!