Allowed force download a file

docs/request_data.md

@@ -16,7 +16,7 @@ See request.py for more information
 
 ```python
 from sanic import Sanic
-from sanic.response import json, text
+from sanic.response import json, text, file
 
 @app.route("/json")
 def post_json(request):
@@ -46,4 +46,11 @@ def query_string(request):
 @app.route("/users", methods=["POST",])
 def create_user(request):
     return text("You are trying to create a user with the following POST: %s" % request.body)
+
+
+@app.route("/file/<file_id>", methods=["GET",])
+def download_a_file(request, file_id):
+     def find_path_by_id(file_id):
+         return "/path/to/file.ext"
+    return file(find_path_by_id(file_id), force_download=True)
 ```

sanic/response.py

@@ -153,13 +153,25 @@ def html(body, status=200, headers=None):
                         content_type="text/html; charset=utf-8")
 
 
-async def file(location, mime_type=None, headers=None):
+async def file(location, mime_type=None, headers=None, force_download=False):
+    """
+    Produces a response that serves file content.
+    :param location: Absolute file path
+    :param mime_type: File MIME type
+    :param headers: List of HTTP headers
+    :param force_download: if `True` immediately prompt the user to save 
+    the file directly to the user's disk, without opening it in the browser
+    """
     filename = path.split(location)[-1]
 
     async with open_async(location, mode='rb') as _file:
         out_stream = await _file.read()
-
+    # Do not attempt to render file in browser
-    mime_type = mime_type or guess_type(filename)[0] or 'text/plain'
+    if force_download is True:
+        headers["Content-Disposition"] = "attachment; filename=%s" % filename
+        mime_type = 'application/octet-stream'
+    else:
+        mime_type = mime_type or guess_type(filename)[0] or 'text/plain'
 
     return HTTPResponse(status=200,
                         headers=headers,