tests/heredoctest.py

revset: prevent crash caused by empty group expression while optimizing "and"

An empty group expression "()" generates None in AST, so the optimizer have
to test it before destructuring a tuple. The error message, "missing argument",
is somewhat obscure, but it should be better than crash.

import sys

globalvars = {}
lines = sys.stdin.readlines()
while lines:
    l = lines.pop(0)
    if l.startswith('SALT'):
        print(l[:-1])
    elif l.startswith('>>> '):
        snippet = l[4:]
        while lines and lines[0].startswith('... '):
            l = lines.pop(0)
            snippet += l[4:]
        c = compile(snippet, '<heredoc>', 'single')
        try:
            exec(c, globalvars)
        except Exception as inst:
            print(repr(inst))