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

@@ -18,7 +18,8 @@
 
 import datetime
 import json
-from typing import Literal, TypedDict, Optional, Union, Tuple
+from typing_extensions import Literal, TypedDict
+from typing import Optional, Union, Tuple, List
 
 from absl import logging
 from capirca.lib import aclgenerator
@@ -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 +16,8 @@
 
 import copy
 import json
-from typing import Any, Literal, Tuple, Union
+from typing import Any, Tuple, Union
+from typing_extensions import Literal
 from unittest import mock
 
 from absl.testing import absltest