A clearer implementation of MultiDictView

This makes MultiDictView work with a simple getter/setter pair, rather than
using attributes with implicit leading underscores. Also move MultiDictView
into multidict.py and adds some simple unit tests.

6 files changed, 119 insertions, 108 deletions

diff --git a/netlib/http/__init__.py b/netlib/http/__init__.py
index 9fafa28f..c4eb1d58 100644
--- a/netlib/http/__init__.py
+++ b/netlib/http/__init__.py
@@ -2,13 +2,13 @@ from __future__ import absolute_import, print_function, division
 from .request import Request
 from .response import Response
 from .headers import Headers
-from .message import MultiDictView, decoded
+from .message import decoded
 from . import http1, http2, status_codes
 
 __all__ = [
     "Request",
     "Response",
     "Headers",
-    "MultiDictView", "decoded",
+    "decoded",
     "http1", "http2", "status_codes",
 ]
diff --git a/netlib/http/message.py b/netlib/http/message.py
index db4054b1..9b0180cf 100644
--- a/netlib/http/message.py
+++ b/netlib/http/message.py
@@ -236,72 +236,3 @@ class decoded(object):
     def __exit__(self, type, value, tb):
         if self.ce:
             self.message.encode(self.ce)
-
-
-class MultiDictView(MultiDict):
-    """
-    Some parts in HTTP (Cookies, URL query strings, ...) require a specific data structure: A MultiDict.
-    It behaves mostly like an ordered dict but it can have several values for the same key.
-
-    The MultiDictView provides a MultiDict *view* on an :py:class:`Request` or :py:class:`Response`.
-    That is, it represents a part of the request as a MultiDict, but doesn't contain state/data themselves.
-
-    For example, ``request.cookies`` provides a view on the ``Cookie: ...`` header.
-    Any change to ``request.cookies`` will also modify the ``Cookie`` header.
-    Any change to the ``Cookie`` header will also modify ``request.cookies``.
-
-    Example:
-
-    .. code-block:: python
-
-        # Cookies are represented as a MultiDict.
-        >>> request.cookies
-        MultiDictView[("name", "value"), ("a", "false"), ("a", "42")]
-
-        # MultiDicts mostly behave like a normal dict.
-        >>> request.cookies["name"]
-        "value"
-
-        # If there is more than one value, only the first value is returned.
-        >>> request.cookies["a"]
-        "false"
-
-        # `.get_all(key)` returns a list of all values.
-        >>> request.cookies.get_all("a")
-        ["false", "42"]
-
-        # Changes to the headers are immediately reflected in the cookies.
-        >>> request.cookies
-        MultiDictView[("name", "value"), ...]
-        >>> del request.headers["Cookie"]
-        >>> request.cookies
-        MultiDictView[]  # empty now
-    """
-
-    def __init__(self, attr, message):
-        if False:  # pragma: no cover
-            # We do not want to call the parent constructor here as that
-            # would cause an unnecessary parse/unparse pass.
-            # This is here to silence linters. Message
-            super(MultiDictView, self).__init__(None)
-        self._attr = attr
-        self._message = message  # type: Message
-
-    @staticmethod
-    def _kconv(key):
-        # All request-attributes are case-sensitive.
-        return key
-
-    @staticmethod
-    def _reduce_values(values):
-        # We just return the first element if
-        # multiple elements exist with the same key.
-        return values[0]
-
-    @property
-    def fields(self):
-        return getattr(self._message, "_" + self._attr)
-
-    @fields.setter
-    def fields(self, value):
-        setattr(self._message, self._attr, value)
diff --git a/netlib/http/request.py b/netlib/http/request.py
index ae28084b..056a2d93 100644
--- a/netlib/http/request.py
+++ b/netlib/http/request.py
@@ -10,8 +10,9 @@ from netlib import utils
 from netlib.http import cookies
 from netlib.odict import ODict
 from .. import encoding
+from ..multidict import MultiDictView
 from .headers import Headers
-from .message import Message, _native, _always_bytes, MessageData, MultiDictView
+from .message import Message, _native, _always_bytes, MessageData
 
 # This regex extracts & splits the host header into host and port.
 # Handles the edge case of IPv6 addresses containing colons.
@@ -228,20 +229,25 @@ class Request(Message):
         """
         The request query string as an :py:class:`MultiDictView` object.
         """
-        return MultiDictView("query", self)
+        return MultiDictView(
+            self._get_query,
+            self._set_query
+        )
 
-    @property
-    def _query(self):
+    def _get_query(self):
         _, _, _, _, query, _ = urllib.parse.urlparse(self.url)
         return tuple(utils.urldecode(query))
 
-    @query.setter
-    def query(self, value):
+    def _set_query(self, value):
         query = utils.urlencode(value)
         scheme, netloc, path, params, _, fragment = urllib.parse.urlparse(self.url)
         _, _, _, self.path = utils.parse_url(
                 urllib.parse.urlunparse([scheme, netloc, path, params, query, fragment]))
 
+    @query.setter
+    def query(self, value):
+        self._set_query(value)
+
     @property
     def cookies(self):
         # type: () -> MultiDictView
@@ -250,16 +256,21 @@ class Request(Message):
 
         An empty :py:class:`MultiDictView` object if the cookie monster ate them all.
         """
-        return MultiDictView("cookies", self)
+        return MultiDictView(
+            self._get_cookies,
+            self._set_cookies
+        )
 
-    @property
-    def _cookies(self):
+    def _get_cookies(self):
         h = self.headers.get_all("Cookie")
         return tuple(cookies.parse_cookie_headers(h))
 
+    def _set_cookies(self, value):
+        self.headers["cookie"] = cookies.format_cookie_header(value)
+
     @cookies.setter
     def cookies(self, value):
-        self.headers["cookie"] = cookies.format_cookie_header(value)
+        self._set_cookies(value)
 
     @property
     def path_components(self):
@@ -322,17 +333,18 @@ class Request(Message):
         An empty MultiDictView if the content-type indicates non-form data
         or the content could not be parsed.
         """
-        return MultiDictView("urlencoded_form", self)
+        return MultiDictView(
+            self._get_urlencoded_form,
+            self._set_urlencoded_form
+        )
 
-    @property
-    def _urlencoded_form(self):
+    def _get_urlencoded_form(self):
         is_valid_content_type = "application/x-www-form-urlencoded" in self.headers.get("content-type", "").lower()
         if is_valid_content_type:
             return tuple(utils.urldecode(self.content))
         return ()
 
-    @urlencoded_form.setter
-    def urlencoded_form(self, value):
+    def _set_urlencoded_form(self, value):
         """
         Sets the body to the URL-encoded form data, and adds the appropriate content-type header.
         This will overwrite the existing content if there is one.
@@ -340,21 +352,30 @@ class Request(Message):
         self.headers["content-type"] = "application/x-www-form-urlencoded"
         self.content = utils.urlencode(value)
 
+    @urlencoded_form.setter
+    def urlencoded_form(self, value):
+        self._set_urlencoded_form(value)
+
     @property
     def multipart_form(self):
         """
         The multipart form data as an :py:class:`MultipartFormDict` object.
         None if the content-type indicates non-form data.
         """
-        return MultiDictView("multipart_form", self)
+        return MultiDictView(
+            self._get_multipart_form,
+            self._set_multipart_form
+        )
 
-    @property
-    def _multipart_form(self):
+    def _get_multipart_form(self):
         is_valid_content_type = "multipart/form-data" in self.headers.get("content-type", "").lower()
         if is_valid_content_type:
             return utils.multipartdecode(self.headers, self.content)
         return ()
 
+    def _set_multipart_form(self, value):
+        raise NotImplementedError()
+
     @multipart_form.setter
     def multipart_form(self, value):
-        raise NotImplementedError()
+        self._set_multipart_form(value)
diff --git a/netlib/http/response.py b/netlib/http/response.py
index 6d56fc1f..7d272e10 100644
--- a/netlib/http/response.py
+++ b/netlib/http/response.py
@@ -5,7 +5,8 @@ import time
 
 from . import cookies
 from .headers import Headers
-from .message import Message, _native, _always_bytes, MessageData, MultiDictView
+from .message import Message, _native, _always_bytes, MessageData
+from ..multidict import MultiDictView
 from .. import utils
 
 
@@ -80,21 +81,26 @@ class Response(Message):
         Caveats:
             Updating the attr
         """
-        return MultiDictView("cookies", self)
+        return MultiDictView(
+            self._get_cookies,
+            self._set_cookies
+        )
 
-    @property
-    def _cookies(self):
+    def _get_cookies(self):
         h = self.headers.get_all("set-cookie")
         return tuple(cookies.parse_set_cookie_headers(h))
 
-    @cookies.setter
-    def cookies(self, all_cookies):
+    def _set_cookies(self, value):
         cookie_headers = []
-        for k, v in all_cookies:
+        for k, v in value:
             header = cookies.format_set_cookie_header(k, v[0], v[1])
             cookie_headers.append(header)
         self.headers.set_all("set-cookie", cookie_headers)
 
+    @cookies.setter
+    def cookies(self, value):
+        self._set_cookies(value)
+
     def refresh(self, now=None):
         """
         This fairly complex and heuristic function refreshes a server
diff --git a/netlib/multidict.py b/netlib/multidict.py
index a359d46b..3af7979b 100644
--- a/netlib/multidict.py
+++ b/netlib/multidict.py
@@ -15,13 +15,7 @@ from .utils import Serializable
 
 
 @six.add_metaclass(ABCMeta)
-class MultiDict(MutableMapping, Serializable):
-    def __init__(self, fields=None):
-
-        # it is important for us that .fields is immutable, so that we can easily
-        # detect changes to it.
-        self.fields = tuple(fields) if fields else tuple()  # type: Tuple[Tuple[bytes, bytes], ...]
-
+class _MultiDict(MutableMapping, Serializable):
     def __repr__(self):
         fields = tuple(
             repr(field)
@@ -97,7 +91,7 @@ class MultiDict(MutableMapping, Serializable):
             value
             for k, value in self.fields
             if self._kconv(k) == key
-            ]
+        ]
 
     def set_all(self, key, values):
         """
@@ -173,7 +167,7 @@ class MultiDict(MutableMapping, Serializable):
         if multi:
             return self.fields
         else:
-            return super(MultiDict, self).items()
+            return super(_MultiDict, self).items()
 
     def to_dict(self):
         """
@@ -213,6 +207,12 @@ class MultiDict(MutableMapping, Serializable):
         return cls(tuple(x) for x in state)
 
 
+class MultiDict(_MultiDict):
+    def __init__(self, fields=None):
+        super(MultiDict, self).__init__()
+        self.fields = tuple(fields) if fields else tuple()  # type: Tuple[Tuple[bytes, bytes], ...]
+
+
 @six.add_metaclass(ABCMeta)
 class ImmutableMultiDict(MultiDict):
     def _immutable(self, *_):
@@ -246,3 +246,34 @@ class ImmutableMultiDict(MultiDict):
         ret = self.copy()
         super(ImmutableMultiDict, ret).insert(index, key, value)
         return ret
+
+
+class MultiDictView(_MultiDict):
+    """
+    The MultiDictView provides the MultiDict interface over calculated data.
+    The view itself contains no state - data is retrieved from the parent on
+    request, and stored back to the parent on change.
+    """
+    def __init__(self, getter, setter):
+        self._getter = getter
+        self._setter = setter
+        super(MultiDictView, self).__init__()
+
+    @staticmethod
+    def _kconv(key):
+        # All request-attributes are case-sensitive.
+        return key
+
+    @staticmethod
+    def _reduce_values(values):
+        # We just return the first element if
+        # multiple elements exist with the same key.
+        return values[0]
+
+    @property
+    def fields(self):
+        return self._getter()
+
+    @fields.setter
+    def fields(self, value):
+        return self._setter(value)
diff --git a/test/netlib/test_multidict.py b/test/netlib/test_multidict.py
index ceea3806..5bb65e3f 100644
--- a/test/netlib/test_multidict.py
+++ b/test/netlib/test_multidict.py
@@ -1,5 +1,5 @@
 from netlib import tutils
-from netlib.multidict import MultiDict, ImmutableMultiDict
+from netlib.multidict import MultiDict, ImmutableMultiDict, MultiDictView
 
 
 class _TMulti(object):
@@ -214,4 +214,26 @@ class TestImmutableMultiDict(object):
     def test_with_insert(self):
         md = TImmutableMultiDict()
         assert md.with_insert(0, "foo", "bar").fields == (("foo", "bar"),)
-        assert md.fields == ()
\ No newline at end of file
+
+
+class TParent(object):
+    def __init__(self):
+        self.vals = tuple()
+
+    def setter(self, vals):
+        self.vals = vals
+
+    def getter(self):
+        return self.vals
+
+
+class TestMultiDictView(object):
+    def test_modify(self):
+        p = TParent()
+        tv = MultiDictView(p.getter, p.setter)
+        assert len(tv) == 0
+        tv["a"] = "b"
+        assert p.vals == (("a", "b"),)
+        tv["c"] = "b"
+        assert p.vals == (("a", "b"), ("c", "b"))
+        assert tv["a"] == "b"