[20212][port2alias]: Fix to get right number of return values (#2188)

What I did
Cherry-pick of #1906 to 202012 branch
Fix conflict also few changes done to cherry-pick:

get_port_config function takes asic id as argument in 2019/202012 branches
Keep load_source of port2alias as module, as is used in unit-test in 202012 branch
get_port_config was modified to return different set number of arguments in PR: sonic-net/sonic-buildimage#4222. Changes in this PR is:

To address the different set of return values
To get the ports from all namespaces
To add unit-test
Additional change done over the cherry-pick:
added setup_class method in test case to load single asic mock db, this was done in pfcwd_test teardown method in 201911 and master branches. It is not done in 202012 branch, hence added setup_class method.

How I did it
Modify port2alias to read ports from all namespaces and also add unit-test

How to verify it
Verified on single and multi-asic DUTs with 202012 image.

scripts/port2alias

@@ -1,11 +1,25 @@
 #!/usr/bin/env python3
 
 import sys
+import os
 from io import StringIO
 
 from portconfig import get_port_config
 from sonic_py_common import device_info
+from sonic_py_common import multi_asic
 
+# mock the redis for unit test purposes #
+try:
+    if os.environ["UTILITIES_UNIT_TESTING"] == "2":
+        modules_path = os.path.join(os.path.dirname(__file__), "..")
+        test_path = os.path.join(modules_path, "tests")
+        sys.path.insert(0, modules_path)
+        sys.path.insert(0, test_path)
+        import mock_tables.dbconnector
+        import mock_tables.mock_multi_asic
+        mock_tables.dbconnector.load_namespace_config()
+except KeyError:
+    pass
 
 def translate_line(line, ports):
     allowed_symbols = ['-', '_']
@@ -15,7 +29,7 @@ def translate_line(line, ports):
     while end < len(line):
         if line[end].isalnum() or line[end] in allowed_symbols:
             pass
-        else: 
+        else:
             # End of a word
             word = line[start:end]
             if word in ports:
@@ -35,7 +49,10 @@ def translate_line(line, ports):
 
 def main():
     (platform, hwsku) = device_info.get_platform_and_hwsku()
-    (ports, _) = get_port_config(hwsku, platform)
+    ports = {}
+    for ns in multi_asic.get_namespace_list():
+        (ports_ns, _, _) = get_port_config(hwsku=hwsku, platform=platform, asic_name=ns)
+        ports.update(ports_ns)
     for line in sys.stdin:
         sys.stdout.write(translate_line(line, ports))
 

tests/port2alias_test.py

@@ -1,12 +1,25 @@
 import sys
 import os
 from unittest import TestCase
+from unittest import mock
+from mock import patch
+from io import StringIO 
+import tests.mock_tables.dbconnector
+import importlib
 
 import imp
 
 port2alias = imp.load_source('port2alias', os.path.join(os.path.dirname(__file__), '..', 'scripts', 'port2alias'))
 
 class TestPort2Alias(TestCase):
+    @classmethod
+    def setup_class(cls):
+        os.environ['UTILITIES_UNIT_TESTING'] = "0"
+        from .mock_tables import dbconnector
+        from .mock_tables import mock_single_asic
+        importlib.reload(mock_single_asic)
+        dbconnector.load_namespace_config()
+
     def setUp(self):
         self.ports = {
                 "Ethernet1": {"alias" : "fortyG0/1"},
@@ -15,6 +28,12 @@ def setUp(self):
                 "Ethernet_11": {"alias" : "fortyG0/11"},
                 }
 
+    @mock.patch('sys.stdout.write')
+    def test_main(self, mock_stdout):
+        with patch('sys.stdin', StringIO("Ethernet0")):
+            port2alias.main()
+            mock_stdout.assert_called_with("etp1")
+
     def test_translate_line_single_word(self):
         self.assertEqual(port2alias.translate_line("1", self.ports),"1")
         self.assertEqual(port2alias.translate_line("1\n", self.ports),"1\n")
@@ -39,3 +58,27 @@ def test_translate_line_multiple_words(self):
     def test_translate_line_empty_ports(self):
         self.assertEqual(port2alias.translate_line("Ethernet1\n", {}),"Ethernet1\n")
 
+class TestPort2AliasNamespace(TestCase):
+    @classmethod
+    def setup_class(cls):
+        os.environ['UTILITIES_UNIT_TESTING'] = "2"
+        from .mock_tables import dbconnector
+        from .mock_tables import mock_multi_asic
+        importlib.reload(mock_multi_asic)
+        dbconnector.load_namespace_config()
+
+    @mock.patch('sys.stdout.write')
+    def test_main(self, mock_stdout):
+        with patch('sys.stdin', StringIO("Ethernet0")):
+            port2alias.main()
+            mock_stdout.assert_called_with("Ethernet1/1")
+
+    @classmethod
+    def teardown_class(cls):
+        print("TEARDOWN")
+        os.environ['UTILITIES_UNIT_TESTING'] = "0"
+        # change back to single asic config
+        from .mock_tables import dbconnector
+        from .mock_tables import mock_single_asic
+        importlib.reload(mock_single_asic)
+        dbconnector.load_namespace_config()