Ihor Radchenko <yantar92@posteo.net> writes:

> Here is the plan to resolve this issue:
>
> 1. We update the manual allowing src blocks to have empty language spec

See the attached patch.

> 2. We update org-syntax document

It turned out to be unnecessary.  org-syntax document already declares
block DATA to be optional:

#+begin_name [DATA]
#+end_name

See https://orgmode.org/worg/org-syntax.html#Blocks

Code blocks fall within a subset of this rule.

> 3. We change org-html-src-block to add caption to src blocks without lang

See the attached patch.