Honor case-insensitivity of metadata keys using FoldedCase.

importlib_metadata/_adapters.py

@@ -2,6 +2,8 @@
 import textwrap
 import email.message
 
+from ._functools import method_cache
+
 
 class Message(email.message.Message):
     def __new__(cls, orig: email.message.Message):
@@ -34,18 +36,22 @@ def json(self):
         Convert PackageMetadata to a JSON-compatible format
         per PEP 0566.
         """
-        # TODO: Need to match case-insensitive
-        multiple_use = {
-            'Classifier',
-            'Obsoletes-Dist',
-            'Platform',
-            'Project-URL',
-            'Provides-Dist',
-            'Provides-Extra',
-            'Requires-Dist',
-            'Requires-External',
-            'Supported-Platform',
-        }
+        multiple_use = set(
+            map(
+                FoldedCase,
+                [
+                    'Classifier',
+                    'Obsoletes-Dist',
+                    'Platform',
+                    'Project-URL',
+                    'Provides-Dist',
+                    'Provides-Extra',
+                    'Requires-Dist',
+                    'Requires-External',
+                    'Supported-Platform',
+                ],
+            )
+        )
 
         def transform(key):
             value = self.get_all(key) if key in multiple_use else self[key]
@@ -54,4 +60,100 @@ def transform(key):
             tk = key.lower().replace('-', '_')
             return tk, value
 
-        return dict(map(transform, self))
+        return dict(map(transform, map(FoldedCase, self)))
+
+
+# from jaraco.text 3.5
+class FoldedCase(str):
+    """
+    A case insensitive string class; behaves just like str
+    except compares equal when the only variation is case.
+
+    >>> s = FoldedCase('hello world')
+
+    >>> s == 'Hello World'
+    True
+
+    >>> 'Hello World' == s
+    True
+
+    >>> s != 'Hello World'
+    False
+
+    >>> s.index('O')
+    4
+
+    >>> s.split('O')
+    ['hell', ' w', 'rld']
+
+    >>> sorted(map(FoldedCase, ['GAMMA', 'alpha', 'Beta']))
+    ['alpha', 'Beta', 'GAMMA']
+
+    Sequence membership is straightforward.
+
+    >>> "Hello World" in [s]
+    True
+    >>> s in ["Hello World"]
+    True
+
+    You may test for set inclusion, but candidate and elements
+    must both be folded.
+
+    >>> FoldedCase("Hello World") in {s}
+    True
+    >>> s in {FoldedCase("Hello World")}
+    True
+
+    String inclusion works as long as the FoldedCase object
+    is on the right.
+
+    >>> "hello" in FoldedCase("Hello World")
+    True
+
+    But not if the FoldedCase object is on the left:
+
+    >>> FoldedCase('hello') in 'Hello World'
+    False
+
+    In that case, use in_:
+
+    >>> FoldedCase('hello').in_('Hello World')
+    True
+
+    >>> FoldedCase('hello') > FoldedCase('Hello')
+    False
+    """
+
+    def __lt__(self, other):
+        return self.lower() < other.lower()
+
+    def __gt__(self, other):
+        return self.lower() > other.lower()
+
+    def __eq__(self, other):
+        return self.lower() == other.lower()
+
+    def __ne__(self, other):
+        return self.lower() != other.lower()
+
+    def __hash__(self):
+        return hash(self.lower())
+
+    def __contains__(self, other):
+        return super(FoldedCase, self).lower().__contains__(other.lower())
+
+    def in_(self, other):
+        "Does self appear in other?"
+        return self in FoldedCase(other)
+
+    # cache lower since it's likely to be called frequently.
+    @method_cache
+    def lower(self):
+        return super(FoldedCase, self).lower()
+
+    def index(self, sub):
+        return self.lower().index(sub.lower())
+
+    def split(self, splitter=' ', maxsplit=0):
+        pattern = re.compile(re.escape(splitter), re.I)
+        return pattern.split(self, maxsplit)