New View base class (#2080)

* New View base class, closes #2078
* Use new View subclass for PatternPortfolioView

datasette/app.py

@@ -17,6 +17,7 @@ import secrets
 import sys
 import threading
 import time
+import types
 import urllib.parse
 from concurrent import futures
 from pathlib import Path
@@ -1361,7 +1362,7 @@ class Datasette:
             r"/-/allow-debug$",
         )
         add_route(
-            PatternPortfolioView.as_view(self),
+            wrap_view(PatternPortfolioView, self),
             r"/-/patterns$",
         )
         add_route(DatabaseDownload.as_view(self), r"/(?P<database>[^\/\.]+)\.db$")
@@ -1673,7 +1674,42 @@ def _cleaner_task_str(task):
     return _cleaner_task_str_re.sub("", s)
 
 
-def wrap_view(view_fn, datasette):
+def wrap_view(view_fn_or_class, datasette):
+    is_function = isinstance(view_fn_or_class, types.FunctionType)
+    if is_function:
+        return wrap_view_function(view_fn_or_class, datasette)
+    else:
+        if not isinstance(view_fn_or_class, type):
+            raise ValueError("view_fn_or_class must be a function or a class")
+        return wrap_view_class(view_fn_or_class, datasette)
+
+
+def wrap_view_class(view_class, datasette):
+    async def async_view_for_class(request, send):
+        instance = view_class()
+        if inspect.iscoroutinefunction(instance.__call__):
+            return await async_call_with_supported_arguments(
+                instance.__call__,
+                scope=request.scope,
+                receive=request.receive,
+                send=send,
+                request=request,
+                datasette=datasette,
+            )
+        else:
+            return call_with_supported_arguments(
+                instance.__call__,
+                scope=request.scope,
+                receive=request.receive,
+                send=send,
+                request=request,
+                datasette=datasette,
+            )
+
+    return async_view_for_class
+
+
+def wrap_view_function(view_fn, datasette):
     @functools.wraps(view_fn)
     async def async_view_fn(request, send):
         if inspect.iscoroutinefunction(view_fn):

datasette/views/base.py

@@ -53,6 +53,43 @@ class DatasetteError(Exception):
         self.message_is_html = message_is_html
 
 
+class View:
+    async def head(self, request, datasette):
+        if not hasattr(self, "get"):
+            return await self.method_not_allowed(request)
+        response = await self.get(request, datasette)
+        response.body = ""
+        return response
+
+    async def method_not_allowed(self, request):
+        if (
+            request.path.endswith(".json")
+            or request.headers.get("content-type") == "application/json"
+        ):
+            response = Response.json(
+                {"ok": False, "error": "Method not allowed"}, status=405
+            )
+        else:
+            response = Response.text("Method not allowed", status=405)
+        return response
+
+    async def options(self, request, datasette):
+        response = Response.text("ok")
+        response.headers["allow"] = ", ".join(
+            method.upper()
+            for method in ("head", "get", "post", "put", "patch", "delete")
+            if hasattr(self, method)
+        )
+        return response
+
+    async def __call__(self, request, datasette):
+        try:
+            handler = getattr(self, request.method.lower())
+        except AttributeError:
+            return await self.method_not_allowed(request)
+        return await handler(request, datasette)
+
+
 class BaseView:
     ds = None
     has_json_alternate = True

datasette/views/special.py

@@ -6,7 +6,7 @@ from datasette.utils import (
     tilde_encode,
     tilde_decode,
 )
-from .base import BaseView
+from .base import BaseView, View
 import secrets
 import urllib
 
@@ -57,13 +57,16 @@ class JsonDataView(BaseView):
             )
 
 
-class PatternPortfolioView(BaseView):
-    name = "patterns"
-    has_json_alternate = False
-
-    async def get(self, request):
-        await self.ds.ensure_permissions(request.actor, ["view-instance"])
-        return await self.render(["patterns.html"], request=request)
+class PatternPortfolioView(View):
+    async def get(self, request, datasette):
+        await datasette.ensure_permissions(request.actor, ["view-instance"])
+        return Response.html(
+            await datasette.render_template(
+                "patterns.html",
+                request=request,
+                view_name="patterns",
+            )
+        )
 
 
 class AuthTokenView(BaseView):