nsxt: Typing fixes for Python 3.6 compatibility.

Ability to run checked mainly by running `docker build --tag=capirca .` and
`docker run capirca`, since the current `Dockerfile` conveniently uses Python
3.6.

To run the tests, a separate `Dockerfile.tests` was used (but not submitted)
with the following changes:

    WORKDIR /app

    ENTRYPOINT ["python3", "-m", "unittest", "discover", "-s", ".", "-p", "nsxt_test.py", "-v"]

and running the test as follows:

    docker build -f Dockerfile.tests --tag capirca:test_nsxt .
    docker run capirca:test_nsxt

Fixes #345.

capirca/lib/nsxt.py

@@ -18,12 +18,13 @@
 
 import datetime
 import json
-from typing import Literal, TypedDict, Optional, Union, Tuple
+from typing import Optional, Union, Tuple, List
 
 from absl import logging
 from capirca.lib import aclgenerator
 from capirca.lib import nacaddr
 from capirca.lib import policy  # for typing information
+from typing_extensions import Literal, TypedDict  # pylint: disable=g-multiple-import
 
 _ACTION_TABLE = {
     'accept': 'ALLOW',
@@ -90,9 +91,9 @@ class NsxtUnsupportedManyPoliciesError(Error):
 class ServiceEntries:
   """Represents service entries for a rule."""
 
-  def __init__(self, protocol: int, source_ports: list[Tuple[str, str]],
-               destination_ports: list[Tuple[str, str]],
-               icmp_types: list[int]):
+  def __init__(self, protocol: int, source_ports: List[Tuple[str, str]],
+               destination_ports: List[Tuple[str, str]],
+               icmp_types: List[int]):
     """Setting things up.
 
     Args:
@@ -239,8 +240,8 @@ def __str__(self):
       af_list = [self.af]
 
     # There can be many source and destination addresses.
-    source_address: list[nacaddr.IPType] = []
-    destination_address: list[nacaddr.IPType] = []
+    source_address: List[nacaddr.IPType] = []
+    destination_address: List[nacaddr.IPType] = []
     source_addr = []
     destination_addr = []
 
@@ -257,32 +258,32 @@ def __str__(self):
       # cannot be a part of a netblock passed into NSX-T API. Currently only
       # addressing IPv4 as that's where the issue has been identified.
       # https://github.com/google/capirca/issues/348
-      zero_ip_address: list[nacaddr.IPType] = []
+      zero_ip_address: List[nacaddr.IPType] = []
       if af == 4:
-        zero_ip_address: list[nacaddr.IPType] = [nacaddr.IP('0.0.0.0/32')]
+        zero_ip_address: List[nacaddr.IPType] = [nacaddr.IP('0.0.0.0/32')]
 
       # source address
       if self.term.source_address:
-        source_address: list[nacaddr.IPType] = self.term.GetAddressOfVersion(
+        source_address: List[nacaddr.IPType] = self.term.GetAddressOfVersion(
             'source_address', af)
-        source_address_exclude: list[nacaddr.IPType] = (
+        source_address_exclude: List[nacaddr.IPType] = (
             self.term.GetAddressOfVersion('source_address_exclude', af))
 
         if source_address_exclude:
-          source_address: list[nacaddr.IPType] = nacaddr.ExcludeAddrs(
+          source_address: List[nacaddr.IPType] = nacaddr.ExcludeAddrs(
               source_address,
               source_address_exclude + zero_ip_address)
         else:
           if (af == 4 and source_address and
               '0.0.0.0/0' not in [str(a) for a in source_address]):
             # Exclude 0.0.0.0/32, removing 0.0.0.0/anything netblocks. However,
             # do so only if we would not already have 'ANY' in the list.
-            source_address: list[nacaddr.IPType] = nacaddr.ExcludeAddrs(
+            source_address: List[nacaddr.IPType] = nacaddr.ExcludeAddrs(
                 source_address, zero_ip_address)
         if source_address:
           if af == 4:
-            source_address: list[nacaddr.IPv4]
-            source_v4_addr: list[nacaddr.IPv4] = source_address
+            source_address: List[nacaddr.IPv4]
+            source_v4_addr: List[nacaddr.IPv4] = source_address
             if (source_v4_addr and
                 '0.0.0.0/0' in [str(a) for a in source_address]):
               # Once we make the address list empty, it'll be set to ANY later
@@ -292,35 +293,35 @@ def __str__(self):
               # later, we'll correctly not use ANY.)
               #
               # See https://github.com/google/capirca/issues/348
-              source_v4_addr: list[nacaddr.IPv4] = []
+              source_v4_addr: List[nacaddr.IPv4] = []
           else:
-            source_address: list[nacaddr.IPv6]
-            source_v6_addr: list[nacaddr.IPv6] = source_address
+            source_address: List[nacaddr.IPv6]
+            source_v6_addr: List[nacaddr.IPv6] = source_address
         source_addr = source_v4_addr + source_v6_addr
 
       # destination address
       if self.term.destination_address:
-        destination_address: list[
+        destination_address: List[
             nacaddr.IPType] = self.term.GetAddressOfVersion(
                 'destination_address', af)
-        destination_address_exclude: list[nacaddr.IPType] = (
+        destination_address_exclude: List[nacaddr.IPType] = (
             self.term.GetAddressOfVersion('destination_address_exclude', af))
 
         if destination_address_exclude:
-          destination_address: list[nacaddr.IPType] = nacaddr.ExcludeAddrs(
+          destination_address: List[nacaddr.IPType] = nacaddr.ExcludeAddrs(
               destination_address,
               destination_address_exclude + zero_ip_address)
         else:
           if (af == 4 and source_address and
               '0.0.0.0/0' not in [str(a) for a in source_address]):
             # Exclude 0.0.0.0/32, removing 0.0.0.0/anything netblocks. However,
             # do so only if we would not already have 'ANY' in the list.
-            destination_address: list[nacaddr.IPType] = nacaddr.ExcludeAddrs(
+            destination_address: List[nacaddr.IPType] = nacaddr.ExcludeAddrs(
                 destination_address, zero_ip_address)
         if destination_address:
           if af == 4:
-            destination_address: list[nacaddr.IPv4]
-            dest_v4_addr: list[nacaddr.IPv4] = destination_address
+            destination_address: List[nacaddr.IPv4]
+            dest_v4_addr: List[nacaddr.IPv4] = destination_address
             if (dest_v4_addr and
                 '0.0.0.0/0' in [str(a) for a in destination_address]):
               # Once we make the address list empty, it'll be set to ANY later
@@ -330,10 +331,10 @@ def __str__(self):
               # later, we'll correctly not use ANY.)
               #
               # See https://github.com/google/capirca/issues/348
-              dest_v4_addr: list[nacaddr.IPv4] = []
+              dest_v4_addr: List[nacaddr.IPv4] = []
           else:
-            destination_address: list[nacaddr.IPv6]
-            dest_v6_addr: list[nacaddr.IPv6] = destination_address
+            destination_address: List[nacaddr.IPv6]
+            dest_v6_addr: List[nacaddr.IPv6] = destination_address
         destination_addr = dest_v4_addr + dest_v6_addr
 
     # Check for mismatch IP for source and destination address for mixed filter
@@ -420,13 +421,13 @@ class Nsxt(aclgenerator.ACLGenerator):
   _FILTER_OPTIONS_DICT = {}
 
   def _TranslatePolicy(self, pol: policy.Policy, exp_info: int):
-    self.nsxt_policies: list[Tuple[policy.Header, str, list[Term]]] = []
+    self.nsxt_policies: List[Tuple[policy.Header, str, List[Term]]] = []
     current_date = datetime.datetime.utcnow().date()
 
     # Warn about policies that will expire in less than exp_info weeks.
     exp_info_date = current_date + datetime.timedelta(weeks=exp_info)
 
-    filters: list[Tuple[policy.Header, list[policy.Term]]] = pol.filters
+    filters: List[Tuple[policy.Header, List[policy.Term]]] = pol.filters
     for header, terms in filters:
       if self._PLATFORM not in header.platforms:
         continue

requirements.txt

@@ -6,3 +6,4 @@ absl-py
 ply
 PyYAML
 six>=1.12.0
+typing_extensions

tests/lib/nsxt_test.py

@@ -16,7 +16,7 @@
 
 import copy
 import json
-from typing import Any, Literal, Tuple, Union
+from typing import Any, Tuple, Union, Dict, List
 from unittest import mock
 
 from absl.testing import absltest
@@ -25,6 +25,7 @@
 from capirca.lib import naming
 from capirca.lib import nsxt
 from capirca.lib import policy
+from typing_extensions import Literal
 
 
 ICMPV6_TERM = """\
@@ -864,14 +865,14 @@ class TestTrafficKindGrid(parameterized.TestCase):
 
   # Which address set should be put into the policy, based on the type of policy
   # we're testing?
-  KIND_TO_ADDRESS: dict[_TRAFFIC_KIND, _ADDRESSES] = {
+  KIND_TO_ADDRESS: Dict[_TRAFFIC_KIND, _ADDRESSES] = {
       'mixed': 'GOOGLE_DNS',
       'v4': 'INTERNAL_V4',
       'v6': 'INTERNAL_V6'}
 
   # Which expanded address group (e.g. netblocks) is expected, based on the type
   # of policy we're testing?
-  KIND_TO_ADDRESS_GROUPS: dict[
+  KIND_TO_ADDRESS_GROUPS: Dict[
       _TRAFFIC_KIND, Union[nacaddr.IPv4, nacaddr.IPv6, Literal['ANY']]] = {
           # 'GOOGLE_DNS'
           'mixed': [nacaddr.IP('8.8.4.4/32'), nacaddr.IP('8.8.8.8/32'),
@@ -961,11 +962,11 @@ def test_generator_works(self):
         '  destination-address:: INTERNAL_V6',
         '}']))
 
-  def get_source_dest_addresses(self, nsxt_json: dict[str, Any]) -> (
-      Tuple[list[str], list[str]]):
-    rules: list[dict[str, Any]] = nsxt_json['rules']
-    src: list[str] = []
-    dst: list[str] = []
+  def get_source_dest_addresses(self, nsxt_json: Dict[str, Any]) -> (
+      Tuple[List[str], List[str]]):
+    rules: List[Dict[str, Any]] = nsxt_json['rules']
+    src: List[str] = []
+    dst: List[str] = []
 
     for rule in rules:
       src.extend(i for i in rule['source_groups'])