Only use the Python typing module if it is available.

10 files changed, 104 insertions, 47 deletions

diff --git a/python/confget/__main__.py b/python/confget/__main__.py
index 26a0279..905877d 100755
--- a/python/confget/__main__.py
+++ b/python/confget/__main__.py
@@ -32,14 +32,17 @@ from __future__ import print_function
 import argparse
 import sys
 
-from typing import List, Optional
-
 from . import backend
 from . import defs
 from . import format as fmt
 
+try:
+    from typing import List, Optional
+
+    _TYPING_USED = (defs, List, Optional)
+except ImportError:
+    pass
 
-_TYPING_USED = (defs, List, Optional)
 
 VERSION_STRING = '2.2.0'
 FEATURES = [
diff --git a/python/confget/backend/__init__.py b/python/confget/backend/__init__.py
index 4cc6ac9..51be726 100644
--- a/python/confget/backend/__init__.py
+++ b/python/confget/backend/__init__.py
@@ -26,12 +26,14 @@
 Provide an interface to all the configuration format backends.
 """
 
-from typing import Dict, Type
-
 from . import abstract, http_get, ini
 
+try:
+    from typing import Dict, Type
 
-_TYPING_USED = (Dict, Type, abstract)
+    _TYPING_USED = (Dict, Type, abstract)
+except ImportError:
+    pass
 
 
 BACKENDS = {
diff --git a/python/confget/backend/abstract.py b/python/confget/backend/abstract.py
index 194976e..1ee2c8d 100644
--- a/python/confget/backend/abstract.py
+++ b/python/confget/backend/abstract.py
@@ -28,14 +28,16 @@ An abstract metaclass for confget backends.
 
 import abc
 
-from typing import Dict
-
 import six
 
 from .. import defs
 
+try:
+    from typing import Dict
 
-_TYPING_USED = (defs, Dict)
+    _TYPING_USED = (defs, Dict)
+except ImportError:
+    pass
 
 
 @six.add_metaclass(abc.ABCMeta)
diff --git a/python/confget/backend/http_get.py b/python/confget/backend/http_get.py
index 9c20e5a..a6f1ba4 100644
--- a/python/confget/backend/http_get.py
+++ b/python/confget/backend/http_get.py
@@ -30,12 +30,17 @@ import os
 import re
 import urllib
 
-from typing import Dict, List
-
 from .. import defs
 
 from . import abstract
 
+try:
+    from typing import Dict, List
+
+    _TYPING_USED = (defs, Dict, List)
+except ImportError:
+    pass
+
 
 try:
     import urllib.parse  # pylint: disable=ungrouped-imports
@@ -45,8 +50,6 @@ except ImportError:
     urllib_unquote = urllib.unquote  # pylint: disable=invalid-name,no-member
 
 
-_TYPING_USED = (defs, Dict, List)
-
 RE_ENTITY = re.compile(r'^ (?P<full> [a-zA-Z0-9_]+ ; )', re.X)
 
 
diff --git a/python/confget/backend/ini.py b/python/confget/backend/ini.py
index bd36fa6..44b9470 100644
--- a/python/confget/backend/ini.py
+++ b/python/confget/backend/ini.py
@@ -29,14 +29,31 @@ A confget backend for reading INI-style files.
 import re
 import sys
 
-from typing import Callable, Dict, Match, NamedTuple, Pattern
-
 from .. import defs
 
 from . import abstract
 
+try:
+    from typing import Callable, Dict, Match, NamedTuple, Pattern
+
+    _TYPING_USED = (defs, Dict)
+
+    MatcherType = NamedTuple('MatcherType', [
+        ('regex', Pattern[str]),
+        ('handle', Callable[[
+            Match[str],
+            Dict[str, str],
+            defs.Config,
+            defs.ConfigData,
+        ], None]),
+    ])
+except ImportError:
+    import collections
 
-_TYPING_USED = (defs, Dict)
+    MatcherType = collections.namedtuple('MatcherType', [  # type: ignore
+        'regex',
+        'handle',
+    ])
 
 
 class INIBackend(abstract.Backend):
@@ -105,15 +122,6 @@ class INIBackend(abstract.Backend):
             if not state['cont']:
                 res[state['section']][state['name']] = state['value']
 
-        MatcherType = NamedTuple('MatcherType', [
-            ('regex', Pattern[str]),
-            ('handle', Callable[[
-                Match[str],
-                Dict[str, str],
-                defs.Config,
-                defs.ConfigData,
-            ], None]),
-        ])
         matches = [
             MatcherType(
                 regex=re.compile(r'^ \s* (?: [#;] .* )? $', re.X),
diff --git a/python/confget/defs.py b/python/confget/defs.py
index f4fa335..7f6a796 100644
--- a/python/confget/defs.py
+++ b/python/confget/defs.py
@@ -26,12 +26,14 @@
 Common definitions for the confget configuration parsing library.
 """
 
-from typing import Dict, List, Optional
+try:
+    from typing import Dict, List, Optional
 
+    _TYPING_USED = (List, Optional)
 
-_TYPING_USED = (List, Optional)
-
-ConfigData = Dict[str, Dict[str, str]]
+    ConfigData = Dict[str, Dict[str, str]]
+except ImportError:
+    pass
 
 
 class Config(object):
diff --git a/python/confget/format.py b/python/confget/format.py
index 1f99aa1..d2265b5 100644
--- a/python/confget/format.py
+++ b/python/confget/format.py
@@ -29,22 +29,32 @@ Filter and format a subset of the configuration variables.
 import fnmatch
 import re
 
-from typing import Callable, Dict, Iterable, NamedTuple, List, Optional
+try:
+    from typing import Callable, Dict, Iterable, NamedTuple, List, Optional
+
+    _TYPING_USED = (Callable, Dict, Iterable, List, Optional)
+
+    FormatOutput = NamedTuple('FormatOutput', [
+        ('name', str),
+        ('value', str),
+        ('output_name', str),
+        ('output_value', str),
+        ('output_full', str),
+    ])
+except ImportError:
+    import collections
+
+    FormatOutput = collections.namedtuple('FormatOutput', [  # type: ignore
+        'name',
+        'value',
+        'output_name',
+        'output_value',
+        'output_full',
+    ])
 
 from . import defs
 
 
-_TYPING_USED = (Callable, Dict, Iterable, List, Optional)
-
-FormatOutput = NamedTuple('FormatOutput', [
-    ('name', str),
-    ('value', str),
-    ('output_name', str),
-    ('output_value', str),
-    ('output_full', str),
-])
-
-
 class FormatConfig(defs.Config):
     # pylint: disable=too-few-public-methods,too-many-instance-attributes
     """
diff --git a/python/tox.ini b/python/tox.ini
index 9b0c5ae..757d546 100644
--- a/python/tox.ini
+++ b/python/tox.ini
@@ -23,7 +23,7 @@
 # SUCH DAMAGE.
 
 [tox]
-envlist = pep8,mypy2,mypy3,prove_2,prove_3,unit_tests_2,unit_tests_3,pylint
+envlist = pep8,mypy2,mypy3,prove_2,prove_2_nt,prove_3,unit_tests_2,unit_tests_2_nt,unit_tests_3,pylint
 skipsdist = True
 
 [testenv:pep8]
@@ -73,6 +73,16 @@ setenv =
 commands =
   pytest -s -vv unit_tests
 
+[testenv:unit_tests_2_nt]
+basepython = python2
+deps =
+  ddt
+  pytest
+setenv =
+  TESTDIR={toxinidir}/../t
+commands =
+  pytest -s -vv unit_tests
+
 [testenv:unit_tests_3]
 basepython = python3
 deps =
@@ -106,6 +116,19 @@ whitelist_externals =
 commands =
   prove ../t
 
+[testenv:prove_2_nt]
+basepython = python2
+deps =
+  six
+setenv =
+  CONFGET=python -m confget
+  MANPAGE={toxinidir}/../confget.1
+  TESTDIR={toxinidir}/../t
+whitelist_externals =
+  prove
+commands =
+  prove ../t
+
 [testenv:prove_3]
 basepython = python3
 deps =
diff --git a/python/unit_tests/data/defs.py b/python/unit_tests/data/defs.py
index b0e2922..759487a 100644
--- a/python/unit_tests/data/defs.py
+++ b/python/unit_tests/data/defs.py
@@ -88,7 +88,8 @@ class XFormNone(XFormType):
 
     def do_xform(self, res):
         # type: (XFormNone, Iterable[cformat.FormatOutput]) -> str
-        return '\n'.join([line.output_full for line in res])
+        xform = '\n'.join([line.output_full for line in res])  # type: str
+        return xform
 
 
 class XFormNewlineToSpace(XFormType):
@@ -101,7 +102,8 @@ class XFormNewlineToSpace(XFormType):
 
     def do_xform(self, res):
         # type: (XFormNewlineToSpace, Iterable[cformat.FormatOutput]) -> str
-        return ''.join([line.output_full + ' ' for line in res])
+        xform = ''.join([line.output_full + ' ' for line in res])  # type: str
+        return xform
 
 
 class XFormCountLines(XFormType):
diff --git a/python/unit_tests/data/load.py b/python/unit_tests/data/load.py
index b954379..cf23f54 100644
--- a/python/unit_tests/data/load.py
+++ b/python/unit_tests/data/load.py
@@ -30,12 +30,14 @@ Load a test definition from a JSON file.
 import json
 import os
 
-from typing import Any, Dict
-
 from . import defs
 
+try:
+    from typing import Any, Dict
 
-TESTING_USED = (defs, Any, Dict)
+    TESTING_USED = (defs, Any, Dict)
+except ImportError:
+    pass
 
 
 def _load_test_v1(data, _version):