Re: [BUG] Inconsistent org-babel tangle behaviour

[Ihor Radchenko <yantar92@posteo.net>]

Thibaut Meyer via "General discussions about Org-mode."
<emacs-orgmode@gnu.org> writes:

> setting a property in an org file like
>
> '#+PROPERTY: header-args    :tangle "file.ext"'
>
> with a source block of the form:
> (note no language is specified for the block)
>
> #+begin_src
> <1: this block won't get tangled>
> #+end_src
>
> won't tangle the block

Currently, source blocks without language are never tangled.

> what's weirder is, just adding to a block the ":tangle" header without
> or with any value, even with the value no, makes the tangling process
> respect the header-args property value and thus the block will tangle
> successfully.
> (note no language is specified for the block)

> #+begin_src :tangle no
> <3: this block will get tangled!!>
> #+end_src

Here, a language is actually specified. The language is ":tangle" (there
is nothing stopping anyone from creating a language name starting from
colon).

> The behaviour doesn't seem super consistent. Ideally, I think having a
> source block like the first one gettin tangled would be good, and having
> the third one not tangle would be better as well.

Src block without language could indeed be tangled in your case.
However, if the :tangle value is set to something like "yes", there is
no way or can deduce the tangle file name.

Note that M-x org-lint warns about src blocks without language. While
src blocks without language are allowed syntactically, many Org features
will not work with such blocks.

Usually, you can simply use "conf" or "text" language name as a
placeholder.

I guess we can support the scenario you described, but I am not sure if
we should.

> The documentation states:
> [Working with source code > Structure of Code Blocks]
> "When ‘<language>’ identifier is omitted, the block also cannot have
> ‘<switches>’ and ‘<header arguments>’."
>
> but, to my knowledge, there is no mention regarding the fact that the
> headers assigned through the "header-args" property should not be
> applied if a block has no language identifier.

That part of the manual can be improved. Maybe something like below.

  When =<language>= identifier is omitted, the block also should not
  have =<switches>= and =<header arguments>=.  Otherwise, the first
  switch/argument will be treated as =<language>=.

Let me know if it clarifies things.

-- 
Ihor Radchenko // yantar92,
Org mode maintainer,
Learn more about Org mode at <https://orgmode.org/>.
Support Org development at <https://liberapay.com/org-mode>,
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