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Re: [PATCH] lisp/ob-core.el: pass expanded body to org-confirm-babel-eva

From: Kyle Meyer
Subject: Re: [PATCH] lisp/ob-core.el: pass expanded body to org-confirm-babel-evaluate
Date: Sun, 19 Jul 2020 17:13:34 -0400

Tom Gillespie writes:

> This is a patch to improve the behavior of
> org-babel-check-confirm-evaluate and the usefulness of
> org-confirm-babel-evaluate when a function is provided.

Thank you.

> This commit changes the behavior of org-babel-check-confirm-evaluate
> so that org-confirm-babel-evaluate receives the fully expanded code to
> be evaluated. This is important because there is no easy way to expand
> noweb references inside org-confirm-babel-evaluate without calling
> org-babel-get-src-block-info a second time. It is also important
> because the current behavior makes it possible for code lurking behind
> noweb references to change without the user being able to detect those
> changes if they trust org-confirm-babel-evaluate is receiving the
> actual body of the code that will be evalulated.

I find that convincing.  I'd guess that a org-confirm-babel-evaluate
function would always want to see expanded noweb references.

This doesn't mention coderefs, though, and the case there seems less
clear.  If there's not a strong reason to strip coderefs, then the new
function wouldn't be necessary, and -check-confirm-evaluate could
instead go with the pattern used elsewhere:

    (if (org-babel-noweb-p (nth 2 info) :eval)
        (org-babel-expand-noweb-references info)
      (nth 1 info))

(Perhaps it'd be worth adding a -maybe-expand variant of
-expand-noweb-references since there are a good number of spots that do
the same params check before calling -expand-noweb-references.)

> These changes were made in such a way as to minimize changes to the
> existing functions, however they come at the cost of making two calls
> to org-babel-get-body-to-eval [...]

Or potentially three calls to -get-body-to-eval: one call with the
-check-evaluate call in -execute-src-block, one with the
-confirm-evaluate in -execute-src-block, and then the direct call to
-get-body-to-eval in -execute-src-block.

> [...] since passing the expanded body through to
> org-confirm-babel-evaluate would either require appending it to the
> info list or changing the function signatures of
> org-babel-confirm-evaluate and org-babel-check-confirm-evaluate which
> is undesireable.  Furthermore, to compute the expanded body only once
> would require switching from using cond in org-babel-execute-src-block
> to using a series of nested ifs. This change can be made, but starting
> from the current implementation will provide a working reference for
> comparison rather than trying to make all the changes at the same
> time.

An option not mentioned above is to replace (nth 1 info) with the
expanded body upstream of (when (org-babel-check-evaluate info) ...).
Modifying the body in INFO is admittedly not pretty, but it's in line
with what is done elsewhere (e.g., -expand-src-block,
-exp-process-buffer, -load-in-session), as well as with how other INFO
elements in -execute-src-block are handled.

In fact, -execute-src-block did modify (nth 1 info) before 3b3fc520a
(Fix coderef handling in source blocks, 2016-08-28), though too late to
affect calls to a org-confirm-babel-evaluate function.  Quickly checking
the tests added in that commit as well as the example in the message [0]
that prompted that commit, modifying (nth 1 info) didn't seem to break
the fix there.

[0] https://orgmode.org/list/87mvjyoja2.fsf@dell-desktop.WORKGROUP

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