Bug fix: use default of ' \t\n' if IFS is unset.

Addresses issue #61.

core/cmd_exec.py

@@ -1121,10 +1121,8 @@ def Execute(self, node, fork_external=True):
      ui.PrettyPrintError(e, self.arena)
      print('osh failed: %s' % e.UserErrorString(), file=sys.stderr)
      status = e.exit_status if e.exit_status is not None else 1
      # TODO: dump self.mem if requested.  Maybe speify with OIL_DUMP_PREFIX.

    # TODO: Hook this up
    #print('break / continue can only be used inside loop')
    #status = 129  # TODO: Fix this.  Use correct macros
    return status

  def RunCommandSub(self, node):

core/legacy.py

@@ -96,7 +96,7 @@ def _GetSplitter(self):
    """Based on the current stack frame, get the splitter."""
    val = self.mem.GetVar('IFS')
    if val.tag == value_e.Undef:
      ifs = ''
      ifs = DEFAULT_IFS
    elif val.tag == value_e.Str:
      ifs = val.s
    else:

spec/word-split.test.sh

@@ -150,6 +150,29 @@ IFS=_
argv.py 1${undefined:-"2_3"x_x"4_5"}6
# stdout: ['12_3x', 'x4_56']

### IFS empty doesn't do splitting
IFS=''
x=$(echo -e ' a b\tc\n')
argv $x
## STDOUT:
[' a b\tc']
## END
## N-I dash STDOUT:
['-e  a b\tc']
## END


### IFS unset behaves like $' \t\n'
unset IFS
x=$(echo -e ' a b\tc\n')
argv $x
## STDOUT:
['a', 'b', 'c']
## END
## N-I dash STDOUT:
['-e', 'a', 'b', 'c']
## END


# TODO:
# - unquoted args of whitespace are not elided (when IFS = null)
@@ -171,3 +194,4 @@ space=" "
AB="A B"
X="X"
Yspaces=" Y "