improve non-string iterable handling

src/rez/resolved_context.py

@@ -6,7 +6,7 @@
 from rez.resolver import Resolver, ResolverStatus
 from rez.system import system
 from rez.config import config
-from rez.util import shlex_join, dedup
+from rez.util import shlex_join, dedup, is_non_string_iterable
 from rez.utils.sourcecode import SourceCodeError
 from rez.utils.colorize import critical, heading, local, implicit, Printer
 from rez.utils.formatting import columnise, PackageRequest, ENV_VAR_REGEX
@@ -1205,7 +1205,7 @@ def execute_shell(self, shell=None, parent_environ=None, rcfile=None,
         """
         sh = create_shell(shell)
 
-        if hasattr(command, "__iter__"):
+        if is_non_string_iterable(command):
             command = sh.join(command)
 
         # start a new session if specified

src/rez/rex.py

@@ -12,7 +12,7 @@
 from rez.system import system
 from rez.config import config
 from rez.exceptions import RexError, RexUndefinedVariableError, RezSystemError
-from rez.util import shlex_join
+from rez.util import shlex_join, is_non_string_iterable
 from rez.utils import reraise
 from rez.utils.system import popen
 from rez.utils.sourcecode import SourceCode, SourceCodeError
@@ -624,7 +624,7 @@ def command(self, value):
         if self.passive:
             return
 
-        if hasattr(value, '__iter__'):
+        if is_non_string_iterable(value):
             it = iter(value)
             cmd = EscapedString.disallow(it.next())
             value = [cmd] + [self.escape_string(x) for x in it]

src/rez/shells.py

@@ -2,7 +2,7 @@
 Pluggable API for creating subshells using different programs, such as bash.
 """
 from rez.rex import RexExecutor, ActionInterpreter, OutputStyle
-from rez.util import shlex_join
+from rez.util import shlex_join, is_non_string_iterable
 from rez.backport.shutilwhich import which
 from rez.utils.logging_ import print_warning
 from rez.utils.system import popen
@@ -379,7 +379,7 @@ def error(self, value):
 
     # escaping is allowed in args, but not in program string
     def command(self, value):
-        if hasattr(value, '__iter__'):
+        if is_non_string_iterable(value):
             it = iter(value)
             cmd = EscapedString.disallow(it.next())
             args_str = ' '.join(self.escape_string(x) for x in it)

src/rez/util.py

@@ -3,13 +3,15 @@
 """
 import stat
 import sys
+import collections
 import atexit
 import os
 import os.path
 import copy
 from rez.exceptions import RezError
 from rez.utils.yaml import dump_yaml
 from rez.vendor.progress.bar import Bar
+from rez.vendor.six import six
 
 
 DEV_NULL = open(os.devnull, 'w')
@@ -95,7 +97,7 @@ def shlex_join(value):
     def quote(s):
         return pipes.quote(s) if '$' not in s else s
 
-    if hasattr(value, '__iter__'):
+    if is_non_string_iterable(value):
         return ' '.join(quote(x) for x in value)
     else:
         return str(value)
@@ -175,6 +177,14 @@ def _atexit():
         pass
 
 
+def is_non_string_iterable(arg):
+    """Python 2 and 3 compatible non-string iterable identifier"""
+
+    return (
+        isinstance(arg, collections.Iterable)
+        and not isinstance(arg, six.string_types)
+    )
+
 # Copyright 2013-2016 Allan Johns.
 #
 # This library is free software: you can redistribute it and/or