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

[Bill Hoffman]

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