zsh: support keg-only ncurses.

[cbarrick]

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The version of ncurses shipping in macOS Mojave is 10 years old. Building against Homebrew's ncurses gives zsh access to an updated terminfo database, e.g. allowing users to set TERM=tmux.

That's exactly my use case: I want to use the tmux terminfo entry with zsh. The easiest way to get highlight/italics right in tmux is to set the TERM appropriately. Ncurses has had tmux and tmux-256color entries in the terminfo database since 2015. The closest thing that the system ncurses has is screen.xterm-new, which is pretty good, but isn't 256color.

The stats on https://formulae.brew.sh/formula/zsh show that someone else has been doing --with-ncurses, so presumably there are other reasons to use a newer ncurses.

Ncurses is not that big of a package (14M). It might be worth it to use Homebrew's version by default.

[fxcoudert]

We're trying to have less options in Homebrew (see rationale in #31510). Either we think this is beneficial for a significant fraction of users, and we enable it by default. Or we think it's an uncommon case, and we'll decline.

[cbarrick]

ncurses is a hard dependency of Zsh. Could we use the keg-only ncurses by default? I've updated the patch to reflect that.

Using an up-to-date terminfo database is particularly useful for a shell. In addition to tmux entries, newer ncurses has terminfo entries for iTerm2 (iterm) and more recent builds of Terminal.app (nsterm-build400).

While it takes some configuration on the user's part to make use of these newer entries (i.e. configuring their terminal to actually use the proper TERM), most common configurations of Zsh use the terminfo entry to derive keybindings etc. oh-my-zsh does this by default.

Again, even in Mojave, the system ncurses is 10 years old!

[cbarrick]

Rebuilding my shell with a modern ncurses is all that I need for my workflow, but it could be useful to build other ncurses apps against a newer version, like vim and tmux. Would this be a course of action supported by the Homebrew core devs? If so, I could open an issue and do some legwork on that. It seems as easy as adding the ncurses dependency to the formula.

[lembacon]

I'm 👍 on building against our ncurses by default. Otherwise users may need to compile their own terminfo database in order to get true color and italics to work appropriately inside tmux.

[lembacon]

I think we could also consider switching tmux and vim to the newer ncurses.

[cbarrick]

For reference, when searching Google for "how to fix italics in tmux" nearly every solution recommends building a custom terminfo entry, with this blog post being what most people refer to.

[cbarrick]

The Jenkins error seems to be network related. It can't reach the documentation URL.

brew audit zsh --online works for me...

[fxcoudert]

Please add a revision 1 line, after sha256.

[cbarrick]

Added the revision 1 after the main sha256. Also rebased on master fwiw.

[lembacon]

Thanks @cbarrick!