Deprecate click.get_terminal_size() in favor of stdlib shutil.get_terminal_size()

[jdufresne]

Since Python 3.3, the stdlib provides the function shutil.get_terminal_size(). Now that the project has dropped Python 2
support, the compatibility shim is no longer necessary.

The stdlib version returns a named tuple. So rather than indexing "0", can use the more self-documenting attribute "columns".

Docs available at: https://docs.python.org/3/library/shutil.html#shutil.get_terminal_size

[janluke]

Maybe I'm missing something but I don't understand the reason for deprecating click.get_terminal_size. Why not just changing its internal implementation?

There's an advantage in defining a "wrapper function" for something you use across your code base: it allows to change implementation without changing all the places where it is used (as long as its interface is the same). In fact, it's the same reason you could have changed just the implementation if you'd not decided to replace all [0] with .columns.

Furthermore, people may have used that function. Why creating a backward incompatibility?

[davidism]

We deprecate things, that's not going to change. I don't have a desire to maintain copies of things that are supported by Python itself.

We've done deprecations plenty of times in all the Pallets projects, removing or changing behavior. This isn't even the only one in the next version of Click. Users will see a DeprecationWarning while running tests, have the opportunity to update their code, then it will be removed in a future version. Projects should also pin their dependency versions to control when and how they do updates and address changes.

[janluke]

@davidism I'm not against all deprecations. I just don't see the advantage of deprecating this particular function.

There's no cost at all in maintaining a wrapper function like click.get_terminal_size; actually using wrapper often decreases the cost of maintenance. If you deprecate it:

• (more work now) you need to change more stuff in this PR and bother about deprecation warnings;
• (more work in the future) you need another commit to actually remove this function; if you decide to change how you get the terminal size in the future, you'll need to change all the places where shutil was used rather than just one place: click.get_terminal_size;
• you introduce a (minor) backward incompatibility.

I can only see overhead for no tangible advantage. That's why I asked. It's not my intention to start a debate about it... I don't care about click.get_terminal_size.