[CMake] ok guys, why is configure_file() so sucky?

[Michael Jackson]

On Aug 17, 2011, at 10:32 AM, Bill Hoffman wrote:

> On 8/17/2011 10:17 AM, Andreas Mohr wrote:
>> [cue maximally inflammatory subject ;)]
>> 
>> Hi,
>> 
>> I keep encountering template file processing where
>> @VAR@ replacements end up empty due to the required template
>> variable simply not having been set (or empty) [or renamed away].
>> Doh.
>> 
>> I'd strongly vote for configure_file() to fail hard in such cases,
>> _by default_.
>> Build system life is already hard enough without all those nice
>> "features" of incomplete/insufficient commands (especially in the
>> packaging area I seem to keep hitting more holes
>> than actual functionality :-P).
>> 
>> So:
>> - change configure_file() behaviour to fail a CMake configure run hard
>>   in case of unavailable (_not_ "empty") @var@ (and perhaps ${var}?),
>>   and have this be the _default_ setting
>> - add configure_file() flag to optionally _disable_ this hard failure
>>   in case it's actually unwanted
>> - add configure_file() flag to optionally enable hard failure for the
>>   other case of existing yet empty variables, too
>> - add policy around this new highly useful feature
>> - hmm, but these things {w|sh}ould apply to both ${xx} and @xx@ - do we need
>>   to have some configuration to tell behaviour apart?
>> - anything I've missed that should be added/changed for a more suitable
>>   implementation?
>> - add these things to a new bug# for implementation
>> 
>> Done Deal?
>> 
> far from...  :)
> 
> If you did that, I am guessing, almost any cmake project using configure_file would hard fail.  Many projects use empty as a value. This is a huge backwards compatibility can of worms... :)
> 
> 
> -Bill

Can you make it an option like "@Only"? @Hard_Fail or @Soft_Fail? You get the idea.

Mike Jackson