taichi.lang.util.warning doesn't respect stdlib warnings filters

[RuRo]

The taichi.lang.util.warning function just prints the warning without consulting the current state of pythons standard library warnings module.

For example:

import warnings
import taichi as ti

with warnings.catch_warnings():
    warnings.simplefilter("ignore")
    ti.lang.util.warning("Oh, no!") # This line shouldn't print anything

with warnings.catch_warnings():
    warnings.simplefilter("error")
    ti.lang.util.warning("Oh, no!") # This line should raise the warning as an exception

You should either

1. use warnings.warn instead of print (preferable, imho)
2. reimplement the standard filtering logic (see here)

Additionally, ti.lang.util.warning prints the errors to stdout instead of the stderr, which is also wrong.

[strongoier]

Thanks for pointing this out! Option 1 looks good to me.
wdyt @ailzhang @frostming

[frostming]

I agree to use the standard warnings.warn and Warning subclasses. Or remove this function entirely(to use the standard warnings.warn)

[ailzhang]

Option 1 sounds great to me! @RuRo would you mind sending a PR to update this function? Thanks a lot!

[RuRo]

Hi, sorry for the delayed reply. Unfortunately, I am kind of busy lately, so I won't be able to contribute anything in the forceable future. I'll keep submitting issues as I run into them while using taichi and I might revisit them once I get some free time. No promises tho, so if anyone wants to contribute it, that would be great.

[pigletfly]

I'd like to take a shot on this @ailzhang

[ailzhang]

@pigletfly Awesome it's yours! Please don't hesitate to ping us here if you have any questions!