mercurial/strutil.py

check-code: catch Python 'is' comparing number or string literals

The Python 'is' operator compares object identity, so it should
definitely not be applied to string or number literals, which Python
implementations are free to represent with a temporary object.

This should catch the following kinds of bogus expressions (examples):

  x is 'foo'     x is not 'foo'
  x is "bar"     x is not "bar"
  x is 42        x is not 42
  x is -36       x is not -36

As originally proposed by Martin Geisler, amended with catching
negative numbers.

# strutil.py - string utilities for Mercurial
#
# Copyright 2006 Vadim Gelfer <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

def findall(haystack, needle, start=0, end=None):
    if end is None:
        end = len(haystack)
    if end < 0:
        end += len(haystack)
    if start < 0:
        start += len(haystack)
    while start < end:
        c = haystack.find(needle, start, end)
        if c == -1:
            break
        yield c
        start = c + 1

def rfindall(haystack, needle, start=0, end=None):
    if end is None:
        end = len(haystack)
    if end < 0:
        end += len(haystack)
    if start < 0:
        start += len(haystack)
    while end >= 0:
        c = haystack.rfind(needle, start, end)
        if c == -1:
            break
        yield c
        end = c - 1