Implement keep_header_casing extension

yt_dlp/networking/_requests.py

@@ -296,6 +296,7 @@ class RequestsRH(RequestHandler, InstanceStoreMixin):
         extensions.pop('cookiejar', None)
         extensions.pop('timeout', None)
         extensions.pop('legacy_ssl', None)
+        extensions.pop('keep_header_casing', None)
 
     def _create_instance(self, cookiejar, legacy_ssl_support=None):
         session = RequestsSession()
@@ -324,6 +325,9 @@ class RequestsRH(RequestHandler, InstanceStoreMixin):
             legacy_ssl_support=request.extensions.get('legacy_ssl'),
         )
 
+        if request.extensions.get('keep_header_casing'):
+            headers = headers.sensitive()
+
         try:
             requests_res = session.request(
                 method=request.method,

yt_dlp/utils/networking.py

@@ -1,9 +1,16 @@
+from __future__ import annotations
+
 import collections
+import collections.abc
 import random
+import typing
 import urllib.parse
 import urllib.request
 
-from ._utils import remove_start
+if typing.TYPE_CHECKING:
+    T = typing.TypeVar('T')
+
+from ._utils import NO_DEFAULT, remove_start
 
 
 def random_user_agent():
@@ -51,32 +58,141 @@ def random_user_agent():
     return _USER_AGENT_TPL % random.choice(_CHROME_VERSIONS)
 
 
-class HTTPHeaderDict(collections.UserDict, dict):
+class HTTPHeaderDict(dict):
     """
     Store and access keys case-insensitively.
     The constructor can take multiple dicts, in which keys in the latter are prioritised.
+
+    Retains a case sensitive mapping of the headers, which can be accessed via `.sensitive()`.
     """
+    def __new__(cls, *args: typing.Any, **kwargs: typing.Any) -> typing.Self:
+        obj = dict.__new__(cls, *args, **kwargs)
+        obj.__sensitive_map = {}
+        return obj
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, /, *args, **kwargs):
         super().__init__()
-        for dct in args:
-            if dct is not None:
-                self.update(dct)
-        self.update(kwargs)
+        self.__sensitive_map = {}
 
-    def __setitem__(self, key, value):
-        if isinstance(value, bytes):
-            value = value.decode('latin-1')
-        super().__setitem__(key.title(), str(value).strip())
+        for dct in filter(None, args):
+            self.update(dct)
+        if kwargs:
+            self.update(kwargs)
 
-    def __getitem__(self, key):
+    def sensitive(self, /) -> dict[str, str]:
+        return {
+            self.__sensitive_map[key]: value
+            for key, value in self.items()
+        }
+
+    def __contains__(self, key: str, /) -> bool:
+        return super().__contains__(key.title() if isinstance(key, str) else key)
+
+    def __delitem__(self, key: str, /) -> None:
+        key = key.title()
+        del self.__sensitive_map[key]
+        super().__delitem__(key)
+
+    def __getitem__(self, key, /) -> str:
         return super().__getitem__(key.title())
 
-    def __delitem__(self, key):
-        super().__delitem__(key.title())
+    def __ior__(self, other, /):
+        if isinstance(other, type(self)):
+            other = other.sensitive()
+        if isinstance(other, dict):
+            self.update(other)
+            return
+        return NotImplemented
 
-    def __contains__(self, key):
-        return super().__contains__(key.title() if isinstance(key, str) else key)
+    def __or__(self, other, /) -> typing.Self:
+        if isinstance(other, type(self)):
+            other = other.sensitive()
+        if isinstance(other, dict):
+            return type(self)(self.sensitive(), other)
+        return NotImplemented
+
+    def __ror__(self, other, /) -> typing.Self:
+        if isinstance(other, type(self)):
+            other = other.sensitive()
+        if isinstance(other, dict):
+            return type(self)(other, self.sensitive())
+        return NotImplemented
+
+    def __setitem__(self, key: str, value, /) -> None:
+        if isinstance(value, bytes):
+            value = value.decode('latin-1')
+        key_title = key.title()
+        self.__sensitive_map[key_title] = key
+        super().__setitem__(key_title, str(value).strip())
+
+    def clear(self, /) -> None:
+        self.__sensitive_map.clear()
+        super().clear()
+
+    def copy(self, /) -> typing.Self:
+        return type(self)(self.sensitive())
+
+    @typing.overload
+    def get(self, key: str, /) -> str | None: ...
+
+    @typing.overload
+    def get(self, key: str, /, default: T) -> str | T: ...
+
+    def get(self, key, /, default=NO_DEFAULT):
+        key = key.title()
+        if default is NO_DEFAULT:
+            return super().get(key)
+        return super().get(key, default)
+
+    @typing.overload
+    def pop(self, key: str, /) -> str: ...
+
+    @typing.overload
+    def pop(self, key: str, /, default: T) -> str | T: ...
+
+    def pop(self, key, /, default=NO_DEFAULT):
+        key = key.title()
+        if default is NO_DEFAULT:
+            self.__sensitive_map.pop(key)
+            return super().pop(key)
+        self.__sensitive_map.pop(key, default)
+        return super().pop(key, default)
+
+    def popitem(self) -> tuple[str, str]:
+        self.__sensitive_map.popitem()
+        return super().popitem()
+
+    @typing.overload
+    def setdefault(self, key: str, /) -> str: ...
+
+    @typing.overload
+    def setdefault(self, key: str, /, default) -> str: ...
+
+    def setdefault(self, key, /, default=None) -> str:
+        key = key.title()
+        if key in self.__sensitive_map:
+            return super().__getitem__(key)
+
+        self[key] = default or ''
+        return self[key]
+
+    def update(self, other, /, **kwargs) -> None:
+        if isinstance(other, type(self)):
+            other = other.sensitive()
+        if isinstance(other, collections.abc.Mapping):
+            for key, value in other.items():
+                self[key] = value
+
+        elif hasattr(other, 'keys'):
+            for key in other.keys():  # noqa: SIM118
+                self[key] = other[key]
+
+        else:
+            for key, value in other:
+                self[key] = value
+
+        for key, value in kwargs.items():
+            self[key] = value
 
 
 std_headers = HTTPHeaderDict({