Template question

Here's the information from README.txt:

Mail Templates
--------------

Go to admin/build/mail_edit to edit the mail templates.

Some of the variables are only available if you save the templates, 
and not at all in digest mode.

However, as long as you DON'T save the templates, they are automatically
translated to the recipient's language. Like other user-modifiable strings, 
when you edit and save them, they stop getting localized. For multi-language
customization, you need to edit the subscriptions_mail.templates.inc file.

You can use conditional text in the templates. The syntax is

   {{!varname==value?then_text:else_text}} or
   {{!varname!=value?then_text:else_text}}

!varname can be the any variable and will be replaced;
value is a string that doesn't contain a '?';
then_text is a string that doesn't contain a ':' and
else_text doesn't have that limitation.

Both then_text and else_text can contain newlines and variables.

Example:
This {{!has_new_comments==1?has:doesn't have any}} new comments.

The left side of !sender_name==!sender_name is replaced, but the right side isn't. The condition is true only when the variable is not set.

This is how variable replacement works everywhere in Drupal, but it might be worth to add this bit here as a reminder.

What help file are you referring to? The link points to this thread.

Since the syntax is !varname==value, much of what you write is redundant.

"Not empty" is not the same as "not defined". A variable could be defined and empty, in which case {{!varname==?... would be true.

How about adding this to README.txt:

Undefined variables are replaced by themselves, i.e. they remain as !varname.
Example:
{{!sender_name==!sender_name?Sender is undefined:Sender: !sender_name}}

Variables can be defined and empty. Example:
{{!sender_name==?Sender is empty:Sender is either undefined or non-empty}}

You are right, there's no way to test that condition. But does that condition need testing?

We're not addressing the end user here but the administrator, and what we're doing is happening before theming. Take !sender_name, for example: it's either undefined or non-empty. Take !body: it's either empty or not, but never undefined (I think). For some fields I've provided predicates (helper variables that are either 0 or 1).

It will take some experimenting to get the templates just right, but I think we've covered all the bases.

The replacement algorithm is the one being used by t(), btw.

I'm (still) not convinced. No one will get a template right with their first shot. It will always take some experimenting. I don't think this ought to be documented in more detail. Just let the administrator find out what works best for them.

We have three states: undefined, empty, and non-empty. Presently, we can test for
-- undefined (or not)
-- empty (or not)
but we cannot test for non-empty.

You're suggesting to treat undefined values as empty, but this would mean we lose information.

And it would mean we'd have to implement our own token replacement algorithm, which would remove every occurrence of an exclamation mark followed by any number of non-blank characters, unless it was matched by a variable.

Ok, my pleasure — thanks for a good discussion!

Good night...