macOS build instructions depend on Homebrew specific configuration

[erlend-aasland]

Comment by Ned in PR #1058:

I like this approach but, as I've just discovered, Homebrew has just changed the game again by making their tcl-tk formula no longer "keg-only". As noted here, we should re-think this a bit in that light. I'll have some more thoughts on it soon.

Originally posted by @ned-deily in #1058 (comment)

[erlend-aasland]

Blocks #1058

[abdnafees]

I can work on this one, I am on macOS.

[CAM-Gerlach]

Seems like this is pending additional analysis by @ned-deily , so I'm not sure there's anything to be done at the moment, @abdnafees ?

[erlend-aasland]

FTR, since it is not explicitly noted already:

The devguide build instructions currently manipulates PKG_CONFIG_PATH, and then incorrectly assumes it is set in the subshells on the same line. Condense example, as shown by Ned in a related issue or PR (I don't have the link at hand):

$ PKG_CONFIG_PATH="$(brew --prefix tcl-tk)/lib/pkgconfig" echo $(pkg-config --libs tcl tk)
Package tcl was not found in the pkg-config search path.
Perhaps you should add the directory containing `tcl.pc'
to the PKG_CONFIG_PATH environment variable
No package 'tcl' found
Package tk was not found in the pkg-config search path.
Perhaps you should add the directory containing `tk.pc'
to the PKG_CONFIG_PATH environment variable
No package 'tk' found

This is not an issue right now, since Homebrew changed their behaviour (also noted by Ned). But it may be an issue if Homebrew changes their behaviour again.

As a first step, we could inline the PGK_CONFI_PATH manipulations into the subshells. Verbose, yes, but it will be correct and safe.

[abdnafees]

Everything went over my head.

[CAM-Gerlach]

@abdnafees Given that and considering that the experts @ned-deily and @erlend-aasland have been taking care of this one, you might want to consider helping with a more accessible issue for a new contributor—there are plenty with a Help Wanted label, as well as others on the main CPython repo and others.

[abdnafees]

@CAM-Gerlach Thank you so much. I will check them out.

[erlend-aasland]

As per the current recommendation, there's nothing to be done here anymore.