#36 add -p --pager flag to page the output using pager crate

[jdvr]

I just added the pager crate and a flag (-p --pager) to enable or disable it.

BTW, I have tested it with Rust 1.28.0 and it works well, maybe you can update.

I would need help for windows and macOS testers.

refs #36

[dbrgn]

Oh, the pager crate looks really nice 🙂 Perfect fit for tealdeer, I think.

[jdvr]

@dbrgn is there any pending issue about this ?

Implemented

[dbrgn]

@dbrgn is there any pending issue about this ?

No, I just needed to find some free time to review 🙂

My main issue with this is currently that the default pager is more, which does not support arrow up/down keys. I think most tools default to less which is more user friendly in that regard.

In my opinion the pager crate should first probe for less, and if found, invoke it with the -r or -R option for color support. Only then it should fall back to more. But maybe more is part of POSIX and less isn't?

We could force less to be used by using Pager::with_pager("less -r").setup(), but then we lose the ability to set another pager with the PAGER env variable, as well as support for the NOPAGER env var... A pull request to pager with a way to override the default (but still allowing env vars) would probably be nice.

Furthermore, it doesn't seem to be supported on Windows:

https://gitlab.com/imp/pager-rs/issues/5

So we should probably exclude the pager functionality when building for Windows.

I'll test the PR on macOS next week.

Regarding defaults, I'm not sure yet whether paging should be the default behavior or not. Probably not, but we can add it to the configuration file once #43 has landed.

[jdvr]

I will keep the -p while #43 is in progress and then we can use the configuration file and implement the use of PAGER env var on our own.

I mean, we can follow a priority to check if the output has to be paged:

1. -p (page always)
2. Enabled in configuration file

Once we know we have to page, check if any pager is configure (PAGER env var or config file), otherwise use less -r.

[dbrgn]

I tested it on macOS. Seems to work generally, but without colors:

Reason is that more is an alias for less, which requires the -r option to render escape codes.

All the more reason to use less -r by default :)

[jdvr]

yep, totally agree, let's change by less -r because it also will work well in most Linux distribution

[dbrgn]

I opened an issue: https://gitlab.com/imp/pager-rs/issues/10

[dbrgn]

It seems that the pager author is willing to add a way to override the default pager. Let's wait for that until we continue with this PR, I guess it should be a matter of weeks :)

[dbrgn]

Released in pager 0.15! This should do:

Pager::with_default_pager("less -R").setup();

Also, in the meantime configfile support was merged 🙂

[jdvr]

Thank you @dbrgn, I will update my PR today. I will also include an option for the configuration file as we commented previously on this thread.

[jdvr]

Totally forgot about this 🙏. I will try to finish the task.

[jdvr]

@dbrgn I have already tested this on Linux with several commands. I think is ready to be merge

[dbrgn]

Some feedback 🙂

[jdvr]

Tanks for the feedback @dbrgn

I have updated the code.

[dbrgn]

Thanks @jdvr!

For some reason the PR deletes the Cargo.lock file, but I can fix that in a manual merge.

[dbrgn]

Huh, what's wrong with Travis... The tests passed but the state wasn't updated.

[jdvr]

I am happy to see this merged after a lot of time 😁

[mystal]

Oh no, this broke Windows support :( pager-rs doesn't support Windows (yet): https://gitlab.com/imp/pager-rs/issues/5

[dbrgn]

Oh, too bad 🤕 We need Windows CI, otherwise this might happen again in the future.

Maybe we could simply disable pager support on Windows?

[mystal]

Yeah, that's a good idea. I'll try to take a look next weekend when I should hopefully have some time.

Aside from that, pager support on Unix sounds great!