From 18413ed1bf08261acf6d40f8ba65a98ae586bb29 Mon Sep 17 00:00:00 2001
From: Armin Ronacher <armin.ronacher@active-4.com>
Date: Sun, 7 Oct 2012 13:02:05 +0200
Subject: [PATCH] Added HTTP override middleware to docs.  This fixes #582

---
 docs/patterns/index.rst           |  1 +
 docs/patterns/methodoverrides.rst | 43 +++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 docs/patterns/methodoverrides.rst

diff --git a/docs/patterns/index.rst b/docs/patterns/index.rst
index 964b1e17..2b1eaa9a 100644
--- a/docs/patterns/index.rst
+++ b/docs/patterns/index.rst
@@ -37,3 +37,4 @@ Snippet Archives <http://flask.pocoo.org/snippets/>`_.
    favicon
    streaming
    deferredcallbacks
+   methodoverrides
diff --git a/docs/patterns/methodoverrides.rst b/docs/patterns/methodoverrides.rst
new file mode 100644
index 00000000..d5c187b6
--- /dev/null
+++ b/docs/patterns/methodoverrides.rst
@@ -0,0 +1,43 @@
+Adding HTTP Method Overrides
+============================
+
+Some HTTP proxies do not support arbitrary HTTP methods or newer HTTP
+methods (such as PATCH).  In that case it's possible to “proxy” HTTP
+methods through another HTTP method in total violation of the protocol.
+
+The way this works is by letting the client do an HTTP POST request and
+set the ``X-HTTP-Method-Override`` header and set the value to the
+intended HTTP method (such as ``PATCH``).
+
+This can easily be accomplished with an HTTP middleware::
+
+    class HTTPMethodOverrideMiddleware(object):
+        allowed_methods = frozenset([
+            'GET',
+            'HEAD',
+            'POST',
+            'DELETE',
+            'PUT',
+            'PATCH',
+            'OPTIONS'
+        ])
+        bodyless_methods = frozenset(['GET', 'HEAD', 'OPTIONS', 'DELETE'])
+
+        def __init__(self, app):
+            self.app = app
+
+        def __call__(self, environ, start_response):
+            method = environ.get('HTTP_X_HTTP_METHOD_OVERRIDE', '').upper()
+            if method in self.allowed_methods:
+                method = method.encode('ascii', 'replace')
+                environ['REQUEST_METHOD'] = method
+            if method in self.bodyless_methods:
+                environ['CONTENT_LENGTH'] = '0'
+            return self.app(environ, start_response)
+
+To use this with Flask this is all that is necessary::
+
+    from flask import Flask
+
+    app = Flask(__name__)
+    app.wsgi_app = HTTPMethodOverrideMiddleware(app.wsgi_app)