Fixed #20147 -- Added HttpRequest.headers.

2 files changed, 88 insertions, 1 deletions

diff --git a/django/http/request.py b/django/http/request.py
index 7dc758d268..02a127d664 100644
--- a/django/http/request.py
+++ b/django/http/request.py
@@ -12,7 +12,9 @@ from django.core.exceptions import (
 )
 from django.core.files import uploadhandler
 from django.http.multipartparser import MultiPartParser, MultiPartParserError
-from django.utils.datastructures import ImmutableList, MultiValueDict
+from django.utils.datastructures import (
+    CaseInsensitiveMapping, ImmutableList, MultiValueDict,
+)
 from django.utils.deprecation import RemovedInDjango30Warning
 from django.utils.encoding import escape_uri_path, iri_to_uri
 from django.utils.functional import cached_property
@@ -65,6 +67,10 @@ class HttpRequest:
             return '<%s>' % self.__class__.__name__
         return '<%s: %s %r>' % (self.__class__.__name__, self.method, self.get_full_path())
 
+    @cached_property
+    def headers(self):
+        return HttpHeaders(self.META)
+
     def _get_raw_host(self):
         """
         Return the HTTP host using the environment or request headers. Skip
@@ -359,6 +365,28 @@ class HttpRequest:
         return list(self)
 
 
+class HttpHeaders(CaseInsensitiveMapping):
+    HTTP_PREFIX = 'HTTP_'
+    # PEP 333 gives two headers which aren't prepended with HTTP_.
+    UNPREFIXED_HEADERS = {'CONTENT_TYPE', 'CONTENT_LENGTH'}
+
+    def __init__(self, environ):
+        headers = {}
+        for header, value in environ.items():
+            name = self.parse_header_name(header)
+            if name:
+                headers[name] = value
+        super().__init__(headers)
+
+    @classmethod
+    def parse_header_name(cls, header):
+        if header.startswith(cls.HTTP_PREFIX):
+            header = header[len(cls.HTTP_PREFIX):]
+        elif header not in cls.UNPREFIXED_HEADERS:
+            return None
+        return header.replace('_', '-').title()
+
+
 class QueryDict(MultiValueDict):
     """
     A specialized MultiValueDict which represents a query string.
diff --git a/django/utils/datastructures.py b/django/utils/datastructures.py
index c5bda0056a..191c2348f6 100644
--- a/django/utils/datastructures.py
+++ b/django/utils/datastructures.py
@@ -1,5 +1,6 @@
 import copy
 from collections import OrderedDict
+from collections.abc import Mapping
 
 
 class OrderedSet:
@@ -280,3 +281,61 @@ class DictWrapper(dict):
         if use_func:
             return self.func(value)
         return value
+
+
+def _destruct_iterable_mapping_values(data):
+    for i, elem in enumerate(data):
+        if len(elem) != 2:
+            raise ValueError(
+                'dictionary update sequence element #{} has '
+                'length {}; 2 is required.'.format(i, len(elem))
+            )
+        if not isinstance(elem[0], str):
+            raise ValueError('Element key %r invalid, only strings are allowed' % elem[0])
+        yield tuple(elem)
+
+
+class CaseInsensitiveMapping(Mapping):
+    """
+    Mapping allowing case-insensitive key lookups. Original case of keys is
+    preserved for iteration and string representation.
+
+    Example::
+
+        >>> ci_map = CaseInsensitiveMapping({'name': 'Jane'})
+        >>> ci_map['Name']
+        Jane
+        >>> ci_map['NAME']
+        Jane
+        >>> ci_map['name']
+        Jane
+        >>> ci_map  # original case preserved
+        {'name': 'Jane'}
+    """
+
+    def __init__(self, data):
+        if not isinstance(data, Mapping):
+            data = {k: v for k, v in _destruct_iterable_mapping_values(data)}
+        self._store = {k.lower(): (k, v) for k, v in data.items()}
+
+    def __getitem__(self, key):
+        return self._store[key.lower()][1]
+
+    def __len__(self):
+        return len(self._store)
+
+    def __eq__(self, other):
+        return isinstance(other, Mapping) and {
+            k.lower(): v for k, v in self.items()
+        } == {
+            k.lower(): v for k, v in other.items()
+        }
+
+    def __iter__(self):
+        return (original_key for original_key, value in self._store.values())
+
+    def __repr__(self):
+        return repr({key: value for key, value in self._store.values()})
+
+    def copy(self):
+        return self