Add simple download progress option

[arenasys]

Closes #11508, continuation of #12084.

GUI software using pip cant show download progress to the user since rich progress bars dont work through pipes, making large downloads quite unfriendly for users. These progress reports are the only information thats missing from pip outputs when running through pipes.

This PR adds a simple progress_bar option called 'raw', which outputs reports to stdout:

Downloading PyQt5-5.15.10-cp37-abi3-manylinux_2_17_x86_64.whl (8.2 MB)
Progress 0 of 8239447
Progress 10240 of 8239447
Progress 583680 of 8239447
Progress 1351680 of 8239447
Progress 2222080 of 8239447
...
Progress 8239447 of 8239447

These are rate limited to reduce spam.

[arenasys]

With just these reports something like tqdm can wrap pip's downloads easily (and more importantly GUI's can).

import sys
import subprocess
import tqdm

args = [sys.executable, '-m', 'pip', 'install', '-I', '--no-cache-dir', 'pyqt5', '--progress-bar=raw']
process = subprocess.Popen(args, stdout=subprocess.PIPE, text=True)

bar, file, last = None, None, None
while line := process.stdout.readline():
    if line.startswith("Downloading"):
        file = line.split(' ', maxsplit=2)[1]
        if type(bar) != type(None):
            bar.close()
    if line.startswith("Progress"):
        _, current, _, total = line.split(' ')
        current, total = int(current), int(total)

        if current == 0:
            bar = tqdm.tqdm(desc=file, total=total, unit='iB', unit_scale=True, unit_divisor=1024)
            last = 0

        bar.update(current - last)
        last = current

PyQt5-5.15.10-cp37-abi3-manylinux_2_17_x86_64.whl: 100%|███████████████████████| 7.86M/7.86M [00:02<00:00, 3.47MiB/s]
PyQt5_Qt5-5.15.2-py3-none-manylinux2014_x86_64.whl: 100%|██████████████████████| 57.1M/57.1M [00:21<00:00, 2.77MiB/s]
PyQt5_sip-12.13.0-cp311-cp311-manylinux_2_5_x86_64.manylinux1_x86_64.whl: 100%|███| 339k/339k [00:01<00:00, 251kiB/s]

[uranusjr]

Not sure about naming this “raw” but I don’t have an immediate suggestion either.

[arenasys]

Can guess from the name alone that its not for regular users and its probably for a more technical purpose, its literally the raw progress without any additional information. Name it 'simple' and users may expect something different. That's my reasoning anyway.

[uranusjr]

Yeah I’m definitely not advocating for simple. Was more thinking about more like machine.

[arenasys]

Could do. But none of Pip's outputs are guaranteed to be machine readable or to remain consistent, its all for humans to read. May give the wrong idea.

[joeyballentine]

I agree with using "raw", I think it makes the most sense for what it does.