New JSON design for query views (#2118)

* Refs #2111, closes #2110
* New Context dataclass/subclass mechanism, refs #2127
* Define QueryContext and extract get_tables() method, refs #2127
* Fix OPTIONS bug by porting DaatbaseView to be a View subclass
* Expose async_view_for_class.view_class for test_routes test
* Error/truncated aruments for renderers, closes #2130

datasette/__init__.py

@@ -1,6 +1,7 @@
-from datasette.permissions import Permission
+from datasette.permissions import Permission  # noqa
 from datasette.version import __version_info__, __version__  # noqa
 from datasette.utils.asgi import Forbidden, NotFound, Request, Response  # noqa
 from datasette.utils import actor_matches_allow  # noqa
+from datasette.views import Context  # noqa
 from .hookspecs import hookimpl  # noqa
 from .hookspecs import hookspec  # noqa

datasette/app.py

@@ -1,7 +1,8 @@
 import asyncio
-from typing import Sequence, Union, Tuple, Optional, Dict, Iterable
+from typing import Any, Dict, Iterable, List, Optional, Sequence, Tuple, Union
 import asgi_csrf
 import collections
+import dataclasses
 import datetime
 import functools
 import glob
@@ -33,6 +34,7 @@
 from jinja2.environment import Template
 from jinja2.exceptions import TemplateNotFound
 
+from .views import Context
 from .views.base import ureg
 from .views.database import database_download, DatabaseView, TableCreateView
 from .views.index import IndexView
@@ -1115,7 +1117,11 @@ def _register_renderers(self):
             )
 
     async def render_template(
-        self, templates, context=None, request=None, view_name=None
+        self,
+        templates: Union[List[str], str, Template],
+        context: Optional[Union[Dict[str, Any], Context]] = None,
+        request: Optional[Request] = None,
+        view_name: Optional[str] = None,
     ):
         if not self._startup_invoked:
             raise Exception("render_template() called before await ds.invoke_startup()")
@@ -1126,6 +1132,8 @@ async def render_template(
             if isinstance(templates, str):
                 templates = [templates]
             template = self.jinja_env.select_template(templates)
+        if dataclasses.is_dataclass(context):
+            context = dataclasses.asdict(context)
         body_scripts = []
         # pylint: disable=no-member
         for extra_script in pm.hook.extra_body_script(
@@ -1368,7 +1376,8 @@ def add_route(view, regex):
             r"/(?P<database>[^\/\.]+)\.db$",
         )
         add_route(
-            DatabaseView.as_view(self), r"/(?P<database>[^\/\.]+)(\.(?P<format>\w+))?$"
+            wrap_view(DatabaseView, self),
+            r"/(?P<database>[^\/\.]+)(\.(?P<format>\w+))?$",
         )
         add_route(TableCreateView.as_view(self), r"/(?P<database>[^\/\.]+)/-/create$")
         add_route(
@@ -1707,6 +1716,7 @@ async def async_view_for_class(request, send):
                 datasette=datasette,
             )
 
+    async_view_for_class.view_class = view_class
     return async_view_for_class
 
 

datasette/renderer.py

@@ -27,7 +27,7 @@ def convert_specific_columns_to_json(rows, columns, json_cols):
     return new_rows
 
 
-def json_renderer(args, data, view_name):
+def json_renderer(args, data, error, truncated=None):
     """Render a response as JSON"""
     status_code = 200
 
@@ -47,8 +47,15 @@ def json_renderer(args, data, view_name):
     # Deal with the _shape option
     shape = args.get("_shape", "objects")
     # if there's an error, ignore the shape entirely
-    if data.get("error"):
+    data["ok"] = True
+    if error:
         shape = "objects"
+        status_code = 400
+        data["error"] = error
+        data["ok"] = False
+
+    if truncated is not None:
+        data["truncated"] = truncated
 
     if shape == "arrayfirst":
         if not data["rows"]:
@@ -64,13 +71,13 @@ def json_renderer(args, data, view_name):
         if rows and columns:
             data["rows"] = [dict(zip(columns, row)) for row in rows]
         if shape == "object":
-            error = None
+            shape_error = None
             if "primary_keys" not in data:
-                error = "_shape=object is only available on tables"
+                shape_error = "_shape=object is only available on tables"
             else:
                 pks = data["primary_keys"]
                 if not pks:
-                    error = (
+                    shape_error = (
                         "_shape=object not available for tables with no primary keys"
                     )
                 else:
@@ -79,8 +86,8 @@ def json_renderer(args, data, view_name):
                         pk_string = path_from_row_pks(row, pks, not pks)
                         object_rows[pk_string] = row
                     data = object_rows
-            if error:
-                data = {"ok": False, "error": error}
+            if shape_error:
+                data = {"ok": False, "error": shape_error}
         elif shape == "array":
             data = data["rows"]
 

datasette/views/__init__.py

@@ -0,0 +1,3 @@
+class Context:
+    "Base class for all documented contexts"
+    pass

datasette/views/base.py

@@ -309,6 +309,8 @@ async def get(self, request):
                 table=data.get("table"),
                 request=request,
                 view_name=self.name,
+                truncated=False,  # TODO: support this
+                error=data.get("error"),
                 # These will be deprecated in Datasette 1.0:
                 args=request.args,
                 data=data,