fix: Do ensure a blank line after a captioned src or example block!

The src and example block captions are wrapped in HTML div tags. As
per CommonMark, the block HTML tags like div tags need to be separated
from Markdown by at least one blank line.

ox-blackfriday.el

@@ -752,8 +752,11 @@ to this rule:
      current item.
 
   3. In an item, if a paragraph is immediately followed by an src
-     or example block (or vice-versa), don't add a blank line
-     between those elements."
+     or example block, don't add a blank line after the paragraph.
+
+  4. In an item, if an src or example block doesn't have a caption
+     and is immediately followed by a paragraph, don't add a blank
+     line after that src or example block."
   (org-element-map tree (remq 'item org-element-all-elements) ;Exception 1 in the doc-string
     (lambda (el)
       (let ((post-blank (cond
@@ -771,9 +774,14 @@ to this rule:
                                (let ((next-el (org-export-get-next-element el info)))
                                  (memq (org-element-type next-el) '(src-block example-block))))
                           0)
-                         ;; Exception 3 in the doc-string (src-block -> paragraph).
+                         ;; Exception 4 in the doc-string (caption-less src-block -> paragraph).
+                         ;; If an src or example block has a caption,
+                         ;; that caption will be wrapped in an HTML
+                         ;; div block. In that case, we *do* need to
+                         ;; leave a blank line after the div block (CommonMark).
                          ((and (memq (org-element-type el) '(src-block example-block))
                                (eq (org-element-type (org-element-property :parent el)) 'item)
+                               (null (org-element-property :caption el)) ;<-- "no caption" check
                                (let ((next-el (org-export-get-next-element el info)))
                                  (memq (org-element-type next-el) '(paragraph))))
                           0)

test/site/content-org/all-posts.org

@@ -1746,20 +1746,26 @@ code block does not have Markdown syntax lists.
 -----
 {{{oxhugoissue(645)}}}
 
-1. item one
-2. This paragraph is followed by a source block *with* caption.
+1. paragraph -> src block with caption -> paragraph -> src block
    #+name: code__foo
    #+caption: Foo
    #+begin_src emacs-lisp
    (message "hey")
    #+end_src
-
-
-1. item one
-2. This paragraph is followed by a source block without caption.
+   sandwiched paragraph
+   #+begin_src emacs-lisp
+   (message "hey")
+   #+end_src
+   last paragraph
+2. paragraph -> src block *without* caption -> paragraph -> src block
+   #+begin_src emacs-lisp
+   (message "hey")
+   #+end_src
+   sandwiched paragraph
    #+begin_src emacs-lisp
    (message "hey")
    #+end_src
+   last paragraph
 **** Source block with list syntax but not in a list
 :PROPERTIES:
 :EXPORT_DATE: 2017-08-01

test/site/content/posts/list-has-src-block-but-no-list-syntax.md

@@ -21,8 +21,7 @@ code block does not have Markdown syntax lists.
 
 `ox-hugo` Issue #[645](https://github.com/kaushalmodi/ox-hugo/issues/645)
 
-1.  item one
-2.  This paragraph is followed by a source block **with** caption.
+1.  paragraph -> src block with caption -> paragraph -> src block
     <a id="code-snippet--foo"></a>
     ```emacs-lisp
     (message "hey")
@@ -32,10 +31,17 @@ code block does not have Markdown syntax lists.
       Foo
     </div>
 
-<!--listend-->
-
-1.  item one
-2.  This paragraph is followed by a source block without caption.
+    sandwiched paragraph
+    ```emacs-lisp
+    (message "hey")
+    ```
+    last paragraph
+2.  paragraph -&gt; src block **without** caption -&gt; paragraph -&gt; src block
+    ```emacs-lisp
+    (message "hey")
+    ```
+    sandwiched paragraph
     ```emacs-lisp
     (message "hey")
     ```
+    last paragraph