Passing arguments from ti CLI to examples

[Hanke98]

Concisely describe the proposed feature

Passing the arguments from ti example ... to the example scripts. e.g.:

ti example stable_fluid -S

I would like this command to pass the arg -S to the stable_fluid.py file and be parsed later.

Describe the solution you'd like (if any)

Actually, the current implementation will pass the args to the examples, however, unrecognized arguments will stop the ti example CLI program. This is because we are using ArgumentParser.parse_args():

taichi/python/taichi/main.py

Line 183 in a866aad

args = parser.parse_args(arguments)

A possible solution is: use ArgumentParser.parse_known_args() and only pass the sys.args[2:] to the downstream.

Additional comments

Note that, if we use ArgumentParser.parse_known_args(), we have to carefully check the args for ti example, since we need to give a user-friendly CLI error prompt.