@jeff-hykin Can you test? I don't use this functionality. Otherwise LGTM.

Yeah, I'm happy too. I might need to wait till next week since I'm got deadlines atm.

Something that might slow it down a bit more is, I'm not sure how point nix towards a specific branch/commit. So advice on that would be appreciated, but I can probably figure it out with the docs if needed. I have to learn it anyways for a separate nix issue.

Edit: Ah looks like you already mentioned how in the issue post
nix-shell -I nixpkgs=/path/to/local/nixpkgs -p opencv4

I'll need python to test with it. e.g. nix-shell -I nixpkgs=./nixpkgs -p opencv4 isn't enough for me to test. Copying from my shell.nix, I tried nix-shell -I nixpkgs=./nixpkgs -p python37.opencv4 but that failed so I'm going to have to spend more time on it another day.

nix-shell -I nixpkgs=./nixpkgs -p opencv4 did compile opencv for me on Sierra without errors though

Note: my system also might not be the most representative since I've got opencv installed in many forms already. I'll use --pure to help limit the external interaction though

@jeff-hykin There are a lot of ways to test this PR. You might want to look into nixpkgs-review

cd to your local checkout of nixpkgs, and run the following command to test:

nixpkgs-review pr --checkout commit  97633 -p opencv4 -p python3Packages.opencv4

You can also just run the following to get a nix-shell with the package available:

nix-shell -I nixpkgs=https://github.com/marsam/nixpkgs/archive/1966a0a4e1c1e07991406e3b90e3b088df252aea.tar.gz -p opencv4 python3Packages.opencv4

I'm merging this as-is, but feel free to open an issue if you find an issue

You can also just run the following to get a nix-shell with the package available:

nix-shell -I nixpkgs=https://github.com/marsam/nixpkgs/archive/1966a0a4e1c1e07991406e3b90e3b088df252aea.tar.gz -p opencv4 python3Packages.opencv4

That is awesome! Thanks @mjlbach

Using that I tested the change just now, and can confirm it works 👍

thanks @marsam for merging this in