Fix bug in REQUIRES for platform_implementation

CHANGELOG.md

@@ -7,6 +7,8 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 
 ## Version 0.15.7 - Unreleased
 
+### Fixed
+* Bug in REQUIRES state did not respect `python_implementation` arguments
 
 ## Version 0.15.6 - Released 2021-08-08
 

xdoctest/directive.py

@@ -343,6 +343,12 @@ def extract(cls, text):
             directive pattern. Because ``xdoctest`` is parsing the text, this issue
             does not occur.
 
+        Example:
+            >>> from xdoctest.directive import Directive, RuntimeState
+            >>> state = RuntimeState()
+            >>> state.update(Directive.extract('# xdoctest: +REQUIRES(CPYTHON)'))
+            >>> list([0].effects()[0]
+
         Example:
             >>> from xdoctest.directive import Directive
             >>> text = '# xdoc: + SKIP'
@@ -409,7 +415,7 @@ def __nice__(self):
             return '{}{}'.format(prefix, self.name)
 
     def _unpack_args(self, num):
-        warnings.warning('Deprecated and will be removed', DeprecationWarning)
+        warnings.warn('Deprecated and will be removed', DeprecationWarning)
         nargs = self.args
         if len(nargs) != 1:
             raise TypeError(
@@ -418,7 +424,7 @@ def _unpack_args(self, num):
         return self.args
 
     def effect(self, argv=None, environ=None):
-        warnings.warning('Deprecated use effects', DeprecationWarning)
+        warnings.warn('Deprecated use effects', DeprecationWarning)
         effects = self.effects(argv=argv, environ=environ)
         if len(effects) > 1:
             raise Exception('Old method cannot hanldle multiple effects')
@@ -572,6 +578,7 @@ def _is_requires_satisfied(arg, argv=None, environ=None):
         bool: flag - True if the requirement is met
 
     Example:
+        >>> from xdoctest.directive import *  # NOQA
         >>> _is_requires_satisfied('PY2', argv=[])
         >>> _is_requires_satisfied('PY3', argv=[])
         >>> _is_requires_satisfied('cpython', argv=[])
@@ -651,12 +658,12 @@ def _is_requires_satisfied(arg, argv=None, environ=None):
         else:
             raise ValueError('Too many expr_parts={}'.format(expr_parts))
     elif arg_lower in SYS_PLATFORM_TAGS:
-        flag = sys.platform.startswith(arg_lower)
+        flag = sys.platform.lower().startswith(arg_lower)
     elif arg_lower in OS_NAME_TAGS:
         flag = os.name.startswith(arg_lower)
     elif arg_lower in PY_IMPL_TAGS:
         import platform
-        flag = platform.python_implementation().startswith(arg_lower)
+        flag = platform.python_implementation().lower().startswith(arg_lower)
     elif arg_lower in PY_VER_TAGS:
         if sys.version_info[0] == 2:  # nocover
             flag = arg_lower == 'py2'