Fix MacOS configuration regex.

[rcurtin]

I found this issue while packaging mlpack for Julia. It seems like the ?: operator isn't supported by CMake regexes, so I adapted them a little bit accordingly. These were the errors being seen:

[15:09:34] CMake Error at CMakeLists.txt:187 (string):
[15:09:34]   string sub-command REGEX, mode REPLACE failed to compile regex
[15:09:34]   "([0-9]+)(?:\.([0-9]+).*)*".
[15:09:34] 
[15:09:34] 
[15:09:34] CMake Error at CMakeLists.txt:192 (string):
[15:09:34]   string sub-command REGEX, mode REPLACE failed to compile regex
[15:09:34]   "([0-9]+)(?:\.([0-9]+).*)*".

from this build log.

[shubham1206agra]

I found this issue while packaging mlpack for Julia. It seems like the ?: operator isn't supported by CMake regexes, so I adapted them a little bit accordingly. These were the errors being seen:

[15:09:34] CMake Error at CMakeLists.txt:187 (string):
[15:09:34]   string sub-command REGEX, mode REPLACE failed to compile regex
[15:09:34]   "([0-9]+)(?:\.([0-9]+).*)*".
[15:09:34] 
[15:09:34] 
[15:09:34] CMake Error at CMakeLists.txt:192 (string):
[15:09:34]   string sub-command REGEX, mode REPLACE failed to compile regex
[15:09:34]   "([0-9]+)(?:\.([0-9]+).*)*".

from this build log.

I have used ?: for a non-capturing group. You can simply remove this and use capture number 3 instead of 2. It also maybe the CMake version issue cause here, all builds are working perfectly as of now.

[shubham1206agra]

Use "([0-9]+)(\\.([0-9]+).*)*" "\\3" instead. Maybe it will help in version string like 10

[rcurtin]

Maybe I misunderstood the original regex---I thought the idea here was to capture the second (minor) version number. So wouldn't it suffice to split out the second ([0-9]+) capture group and use that, and leave the (\\.([0-9]+).*)* to capture (and leave unused) any additional terms in the version number?

[shubham1206agra]

I think the purpose of this regex is to get the second (minor) version number if it exists. Before this fix, we used forced major version 10 and then a minor number. But after that fix, we also took care of major version 11. Now, I don't remember whether it would not break if we didn't include cases with no minor number like "11".

[rcurtin]

Thanks for the explanation; fixed in 28be9de. I tested this and it seems to work fine. 👍

[shubham1206agra]

Looking good to me!

[mlpack-bot]

Second approval provided automatically after 24 hours. 👍

[qazi0]

@rcurtin Any plans to ship this to a patch (4.0.1?) release soon? As this is still broken in 4.0.0 on macos. Had to manually apply the patch from this commit to get it to work

[rcurtin]

@Siraj-Qazi sorry that you had to apply it manually. Let me merge #3322 (today or tomorrow), then I'll open a PR for the 4.0.1 release, which will take a day or two to merge. 👍

[qazi0]

Thanks alot @rcurtin !