[Asterisk-code-review] channel_internal_api: Add LASTCONTEXT and LASTEXTEN (asterisk[master])

[N A]

Attention is currently required from: Sean Bright, Richard Mudgett.
N A has posted comments on this change. ( https://gerrit.asterisk.org/c/asterisk/+/17784 )

Change subject: channel_internal_api: Add LASTCONTEXT and LASTEXTEN
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Patch Set 2:

(1 comment)

Patchset:

PS2: 
> > What applications currently do this?
> 
> Things built by Asterisk users. Things that read/write channel variables (dialplan, AMI, AGI, etc). 

Users aren't supposed to write to all caps variables. So they would use ${lastexten} not ${LASTEXTEN}. If not, that's their fault.

> > As it's all caps, users shouldn't be using this variable (with this case).
> 
> I don’t follow. Is this your opinion or is this documented somewhere?

See Asterisk: The Definitive Guide, 5th edition, pg. 97, for example:

"Note that variable names are case-sensitive. A variable named SOME DIGITS is different from a variable named SomeDigits. You should also be aware that any variables set by Asterisk will be uppercase. Some variables, such as CHANNEL and EXTEN, are reserved by Aster‐ isk. You should not attempt to set these variables"

When I first started with Asterisk, I erroneously used all-caps variable names at times myself. Somebody who'd been using Asterisk since it came out quickly corrected me on that:
"Variable names.  Any Variable name which does not include at least ONE lower-case letter is reserved for use by the Asterisk developers.  You should never use variable names that are all upper case, because you might run into something that gets added in the future or is undocumented."

So using an all-caps variable name is something we have every right to do. It is explicitly documented and intended to be that way. I don't think accounting for people doing things the wrong way changes that.



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Gerrit-Project: asterisk
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Gerrit-Change-Id: Ib455fe300cc8e9a127686896ee2d0bd11e900307
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