Re: good patch vs. sed fixes

On Thu, 2024-11-21 at 03:40 +0100, Uwe Düffert wrote:
> Hi all,
> 
> I'm not sure it is worth the effort, but from time to time I stumble 
> across the "problem" that certain sed or patch commands would apply 
> multiple times although they should not. I'm fully aware this is 
> unsupported "deviating from the book" but it happens. I'm trying to build 
> some not-yet-in-the-book new version, something fails, I fix the problem 
> and try again, then some unexpected "double sed" or "double patch" 
> silently breaks stuff. Sure, I should have done it cleanly from scratch, 
> but the nature of the fixed problem suggested I could just repeat the 
> build...

Then why not just issue "./mach build"?  Why the sed is ever executed
again?

/* snip */

> I do like the idea to fix stuff with a simple sed if it helps avoiding a 
> patch, BUT only if it does the job similarily well.

It is doing things similarity well.  If not it wouldn't be in the book
in the first place.

> I kind of appreciate 
> the educational value of a sophisticated sed, but in my experience 
> a unified patch is less likely to "doubly apply" (though it happened to me 
> before) and sometimes makes clearer what actually needs to be changed.
> 
> I'm not proposing using some more official patch such as 
> https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=d9712b1358dc1b64933c3090d72153aae3270f25 
> in this case, I'd just like to mention that this patch 1) makes the 
> idea more clear (there are not just 5 more CLASS_CHARACTERs but they do 
> have names)

The names are not relevant.  I can rewrite the command as

for i in AKSARA AKSARA_PREBASE AKSARA_START VIRAMA_FINAL VIRAMA; do
   sed -i '/ZWJ/s/}/,CLASS_CHARACTER&/' intl/lwbrk/LineBreaker.cpp 
done

but this is just meaningless to 99.99% BLFS users (who are not an ICU
developer, nor a Mozilla developer, nor a linguist).

> and it does not apply multiple times...

Again, when I just did a code fix to Firefox I just run "./mach build"
and I don't understand why the sed would be executed again.

Sometimes I do deliberately make a sed no-op if applied twice.  But it's
only a bonus, not something we need to guarantee.  And sometimes such a
bonus is a bad thing: when we update the package to a new version where
the fix is already upstream, the editor can easily forget to remove the
sed which is no-op now.  (OTOH if it's just "double applied" the build
fails and the editor immediately notice it.)

-- 
Xi Ruoyao <[email protected]>
School of Aerospace Science and Technology, Xidian University

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