From b1e168b9c907d9b6c37fb3188fa2053baf56d5d1 Mon Sep 17 00:00:00 2001
From: Simon Willison <swillison@gmail.com>
Date: Wed, 1 Jul 2020 14:03:15 -0700
Subject: [PATCH] Incomplete WIP for #880

---
 datasette/views/base.py     |  8 +++++---
 datasette/views/database.py | 11 +++++++++++
 datasette/views/table.py    | 16 +++++++++++++---
 3 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/datasette/views/base.py b/datasette/views/base.py
index 399b1a1f..ed50edeb 100644
--- a/datasette/views/base.py
+++ b/datasette/views/base.py
@@ -356,12 +356,14 @@ class DataView(BaseView):
         if "table_and_format" in args:
             db = self.ds.databases[database]
 
-            async def async_table_exists(t):
-                return await db.table_exists(t)
+            async def async_table_or_query_exists(t):
+                return await db.table_exists(t) or await self.ds.get_canned_query(
+                    database, t, request.actor
+                )
 
             table, _ext_format = await resolve_table_and_format(
                 table_and_format=urllib.parse.unquote_plus(args["table_and_format"]),
-                table_exists=async_table_exists,
+                table_exists=async_table_or_query_exists,
                 allowed_formats=self.ds.renderers.keys(),
             )
             _format = _format or _ext_format
diff --git a/datasette/views/database.py b/datasette/views/database.py
index 9d639170..b85ed757 100644
--- a/datasette/views/database.py
+++ b/datasette/views/database.py
@@ -144,6 +144,7 @@ class QueryView(DataView):
         _size=None,
         named_parameters=None,
         write=False,
+        json_format=False,
     ):
         params = {key: request.args.get(key) for key in request.args}
         if "sql" in params:
@@ -212,6 +213,16 @@ class QueryView(DataView):
                     message = metadata.get("on_error_message") or str(e)
                     message_type = self.ds.ERROR
                     redirect_url = metadata.get("on_error_redirect")
+                if json_format:
+                    return (
+                        {
+                            "message": message,
+                            "message_type": message_type,
+                            "redirect_url": redirect_url,
+                        },
+                        {},
+                        [],
+                    )
                 self.ds.add_message(request, message, message_type)
                 return self.redirect(request, redirect_url or request.path)
             else:
diff --git a/datasette/views/table.py b/datasette/views/table.py
index e0a52e20..3f24a2f6 100644
--- a/datasette/views/table.py
+++ b/datasette/views/table.py
@@ -18,6 +18,7 @@ from datasette.utils import (
     path_with_added_args,
     path_with_removed_args,
     path_with_replaced_args,
+    resolve_table_and_format,
     sqlite3,
     to_css_class,
     urlsafe_components,
@@ -223,9 +224,17 @@ class TableView(RowTableShared):
 
     async def post(self, request, db_name, table_and_format):
         # Handle POST to a canned query
-        canned_query = await self.ds.get_canned_query(
-            db_name, table_and_format, request.actor
+        async def async_query_exists(query):
+            canned_query = await self.ds.get_canned_query(db_name, query, request.actor)
+            return bool(canned_query)
+
+        query, _format = await resolve_table_and_format(
+            table_and_format=urllib.parse.unquote_plus(table_and_format),
+            table_exists=async_query_exists,
+            allowed_formats=self.ds.renderers.keys(),
         )
+
+        canned_query = await self.ds.get_canned_query(db_name, query, request.actor)
         assert canned_query, "You may only POST to a canned query"
         return await QueryView(self.ds).data(
             request,
@@ -234,9 +243,10 @@ class TableView(RowTableShared):
             canned_query["sql"],
             metadata=canned_query,
             editable=False,
-            canned_query=table_and_format,
+            canned_query=query,
             named_parameters=canned_query.get("params"),
             write=bool(canned_query.get("write")),
+            json_format=(_format == "json"),
         )
 
     async def data(