[stringtemplate-interest] Fail on undefined property

[Terence Parr]

On Jul 31, 2009, at 12:48 PM, Sam Harwell wrote:

> The problem is the same code path is used for evaluating conditional
> expressions, where a missing attribute is "false". I believe when the
> write method encounters an undefined property, it *should* throw an
> exception. For example:
>
> Should not throw if x is undefined:
>
> <if(x)><x><endif>
>
> Should throw if x is undefined:
>
> <x>

Well, it's very useful to evaluate to an empty string sometimes.

Hi, <firstname> <lastname>

if you only know the first name, we shouldn't have to gate every  
reference to other attributes to prevent an exception.

> Note that we already do throw an exception in the following case if  
> x is
> defined but has no member f. The behavior should be made consistent,  
> but
> we have to be careful about informing people of the change since it's
> absolutely a breaking change.
>
> <x.f>

When I build the new version, I will make a consistent policy. Most  
likely there will be a choice that the user can set about strictness,  
turning on various bits in a set about what should throw an exception.
T