test: Added some new tests for the parse_content_type function in _he…

…lpers and its use in _metadata

google/auth/_helpers.py

@@ -30,26 +30,6 @@
 REFRESH_THRESHOLD = datetime.timedelta(seconds=20)
 
 
-def parse_content_type(header_value):
-    """Parse a 'content-type' header value to get just the plain media-type (without parameters).
-
-    This is done using the class Message from email.message as suggested in PEP 594
-        (because the cgi is now deprecated and will be removed in python 3.13,
-        see https://peps.python.org/pep-0594/#cgi).
-
-    Args:
-        header_value (str): The value of a 'content-type' header as string.
-
-    Returns:
-        str: A string with just the lowercase media-type from the parsed 'content-type' header.
-            If the provided content-type is not parsable, returns 'text/plain',
-            the default value for textual files.
-    """
-    m = Message()
-    m['content-type'] = header_value
-    return m.get_content_type()
-
-
 def copy_docstring(source_class):
     """Decorator that copies a method's docstring from another class.
 
@@ -84,6 +64,26 @@ def decorator(method):
     return decorator
 
 
+def parse_content_type(header_value):
+    """Parse a 'content-type' header value to get just the plain media-type (without parameters).
+
+    This is done using the class Message from email.message as suggested in PEP 594
+        (because the cgi is now deprecated and will be removed in python 3.13,
+        see https://peps.python.org/pep-0594/#cgi).
+
+    Args:
+        header_value (str): The value of a 'content-type' header as a string.
+
+    Returns:
+        str: A string with just the lowercase media-type from the parsed 'content-type' header.
+            If the provided content-type is not parsable, returns 'text/plain',
+            the default value for textual files.
+    """
+    m = Message()
+    m["content-type"] = header_value
+    return m.get_content_type() # Despite the name, actually returns just the media-type
+
+
 def utcnow():
     """Returns the current UTC datetime.
 

tests/compute_engine/test__metadata.py

@@ -176,6 +176,22 @@ def test_get_success_json():
     assert result[key] == value
 
 
+def test_get_success_json_content_type_charset():
+    key, value = "foo", "bar"
+
+    data = json.dumps({key: value})
+    request = make_request(data, headers={"content-type": "application/json; charset=UTF-8"})
+
+    result = _metadata.get(request, PATH)
+
+    request.assert_called_once_with(
+        method="GET",
+        url=_metadata._METADATA_ROOT + PATH,
+        headers=_metadata._METADATA_HEADERS,
+    )
+    assert result[key] == value
+
+
 def test_get_success_retry():
     key, value = "foo", "bar"
 

tests/test__helpers.py

@@ -51,6 +51,32 @@ def func2():  # pragma: NO COVER
         _helpers.copy_docstring(SourceClass)(func2)
 
 
+def test_parse_content_type_plain():
+    assert _helpers.parse_content_type("text/html")         == "text/html"
+    assert _helpers.parse_content_type("application/xml")   == "application/xml"
+    assert _helpers.parse_content_type("application/json")  == "application/json"
+
+
+def test_parse_content_type_with_parameters():
+    content_type_html   = "text/html; charset=UTF-8"
+    content_type_xml    = "application/xml; charset=UTF-16; version=1.0"
+    content_type_json   = "application/json; charset=UTF-8; indent=2"
+    assert _helpers.parse_content_type(content_type_html)   == "text/html"
+    assert _helpers.parse_content_type(content_type_xml)    == "application/xml"
+    assert _helpers.parse_content_type(content_type_json)   == "application/json"
+
+
+def test_parse_content_type_missing_or_broken():
+    content_type_foo    = None
+    content_type_bar    = ""
+    content_type_baz    = "1234"
+    content_type_qux    = " ; charset=UTF-8"
+    assert _helpers.parse_content_type(content_type_foo)    == "text/plain"
+    assert _helpers.parse_content_type(content_type_bar)    == "text/plain"
+    assert _helpers.parse_content_type(content_type_baz)    == "text/plain"
+    assert _helpers.parse_content_type(content_type_qux)    == "text/plain"
+
+
 def test_utcnow():
     assert isinstance(_helpers.utcnow(), datetime.datetime)