[rest] switch base responses to ABCs

sdk/core/azure-core/azure/core/rest/_http_response_impl.py

@@ -82,6 +82,7 @@ def __init__(self, **kwargs):
         self._json = None  # this is filled in ContentDecodePolicy, when we deserialize
         self._content = None  # type: Optional[bytes]
         self._text = None  # type: Optional[str]
+        self._last_passed_encoding = None
 
     @property
     def request(self):
@@ -184,9 +185,11 @@ def text(self, encoding=None):
          also be set independently through our encoding property
         :return: The response's content decoded as a string.
         """
-        if self._text is None or encoding:
-            encoding_to_pass = encoding or self.encoding
-            self._text = decode_to_text(encoding_to_pass, self.content)
+        if encoding:
+            return decode_to_text(encoding, self.content)
+        if self._text:
+            return self._text
+        self._text = decode_to_text(self.encoding, self.content)
         return self._text
 
     def json(self):

sdk/core/azure-core/tests/test_rest_http_response.py

@@ -314,6 +314,19 @@ def test_text_and_encoding(send_request):
     assert response.text("latin-1") == u'ð\x9f\x91©' == response.content.decode("latin-1")
     assert response.encoding == "utf-16"
 
+def test_passing_encoding_to_text(send_request):
+    response = send_request(
+        request=HttpRequest("GET", "/encoding/emoji"),
+    )
+    assert response.content == u"👩".encode("utf-8")
+    assert response.text() == u"👩"
+
+    # pass in different encoding
+    assert response.text("latin-1") == u'ð\x9f\x91©'
+
+    # check response.text() still gets us the old value
+    assert response.text() == u"👩"
+
 def test_initialize_response_abc():
     with pytest.raises(TypeError) as ex:
         HttpResponse()