On Wed, Aug 17, 2011 at 10:32 AM, Bill Hoffman <bill.hoff...@kitware.com> 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
>
>
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We could do it without a policy and without a can of worms if we
simply add a new command instead of trying to re-use the existing,
perfectly reasonable configure_file command.
Or... by defaulting to the existing behavior and requiring the use of
a new flag to configure_file or setting a variable to indicate the new
STRICT behavior. (I assume you'd be more in favor of a new command
since you said you want this to happen by default.)
One of the main problems with flagging empty variables as "empty" is
that sometimes you intend a variable to be empty... So really, only an
undefined variable should be considered an error.
David
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