[Issue #558] Coerce compiled regex patterns type according to spawn encoding

[EmersonPrado]

This change extends the type coercing already present in exact matches for compiled regex matches. In short: if spawn encoding is None, it changes the compiled regex to have a bytes type pattern. Otherwise, changes to non-bytes type pattern.

[EmersonPrado]

Some tests from myself:

Test code

import re
from lib.pexpect.pexpect import spawn, EOF, TIMEOUT

for spawn_string, encoding in [("ã", None), ("ã", 'ascii'), ("a", 'ascii'), ("ã", 'utf-8')]:
  for pattern in ['ã', b'a', r'ã']:
    try:
      print('Spawn string: "{}"\tSpawn encoding: "{}"\tMatch pattern: "{}"'
            .format(spawn_string, encoding, pattern))
      spawn_object = spawn('echo "{}"'.format(spawn_string), encoding=encoding)
    except UnicodeEncodeError as erro:
      print('Spawn string format and encoding mismatch')
      continue
    index = -1
    while index < 1:
      try:
        index = spawn_object.expect([re.compile(pattern), EOF, TIMEOUT])
      except UnicodeDecodeError as erro:
        print('Invalid pattern')
        break
      if index == 0:
        print('Match')

Before fix

Python 3

Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "ã"
Traceback (most recent call last):
  File "<stdin>", line 12, in <module>
  File "<Pexpect path>/pexpect/spawnbase.py", line 341, in expect
    timeout, searchwindowsize, async_)
  File "<Pexpect path>/pexpect/spawnbase.py", line 369, in expect_list
    return exp.expect_loop(timeout)
  File "<Pexpect path>/pexpect/expect.py", line 103, in expect_loop
    idx = self.new_data(incoming)
  File "<Pexpect path>/pexpect/expect.py", line 29, in new_data
    index = searcher.search(window, len(data))
  File "<Pexpect path>/pexpect/expect.py", line 293, in search
    match = s.search(buffer, searchstart)
TypeError: cannot use a string pattern on a bytes-like object

Python 2

Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "ã"
Match
Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "a"
Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "ã"
Match
Spawn string: "ã"	Spawn encoding: "ascii"	Match pattern: "ã"
Invalid pattern
Spawn string: "ã"	Spawn encoding: "ascii"	Match pattern: "a"
Invalid pattern
Spawn string: "ã"	Spawn encoding: "ascii"	Match pattern: "ã"
Invalid pattern
Spawn string: "a"	Spawn encoding: "ascii"	Match pattern: "ã"
Spawn string: "a"	Spawn encoding: "ascii"	Match pattern: "a"
Match
Spawn string: "a"	Spawn encoding: "ascii"	Match pattern: "ã"
Spawn string: "ã"	Spawn encoding: "utf-8"	Match pattern: "ã"  # Not nice
Spawn string: "ã"	Spawn encoding: "utf-8"	Match pattern: "a"
Spawn string: "ã"	Spawn encoding: "utf-8"	Match pattern: "ã"  # Not nice

After fix

Python 3

Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "ã"
Match
Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "b'a'"
Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "ã"
Match
Spawn string: "ã"	Spawn encoding: "ascii"	Match pattern: "ã"
Spawn string format and encoding mismatch
Spawn string: "ã"	Spawn encoding: "ascii"	Match pattern: "b'a'"
Spawn string format and encoding mismatch
Spawn string: "ã"	Spawn encoding: "ascii"	Match pattern: "ã"
Spawn string format and encoding mismatch
Spawn string: "a"	Spawn encoding: "ascii"	Match pattern: "ã"
Spawn string: "a"	Spawn encoding: "ascii"	Match pattern: "b'a'"
Match
Spawn string: "a"	Spawn encoding: "ascii"	Match pattern: "ã"
Spawn string: "ã"	Spawn encoding: "utf-8"	Match pattern: "ã"
Match
Spawn string: "ã"	Spawn encoding: "utf-8"	Match pattern: "b'a'"
Spawn string: "ã"	Spawn encoding: "utf-8"	Match pattern: "ã"
Match

Python 2

Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "ã"
Match
Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "a"
Spawn string: "ã"	Spawn encoding: "None"	Match pattern: "ã"
Match
Spawn string: "ã"	Spawn encoding: "ascii"	Match pattern: "ã"
Invalid pattern
Spawn string: "ã"	Spawn encoding: "ascii"	Match pattern: "a"
Invalid pattern
Spawn string: "ã"	Spawn encoding: "ascii"	Match pattern: "ã"
Invalid pattern
Spawn string: "a"	Spawn encoding: "ascii"	Match pattern: "ã"
Spawn string: "a"	Spawn encoding: "ascii"	Match pattern: "a"
Match
Spawn string: "a"	Spawn encoding: "ascii"	Match pattern: "ã"
Spawn string: "ã"	Spawn encoding: "utf-8"	Match pattern: "ã"  # Nice
Match
Spawn string: "ã"	Spawn encoding: "utf-8"	Match pattern: "a"
Spawn string: "ã"	Spawn encoding: "utf-8"	Match pattern: "ã"  # Nice
Match

[EmersonPrado]

I messed this thread too much. Sorry for the mess. I'll start over with a fresh branch and PR.