Flash messages mechanism, closes #790

datasette/app.py

@@ -2,6 +2,7 @@ import asyncio
 import collections
 import datetime
 import hashlib
+from http.cookies import SimpleCookie
 import itertools
 import json
 import os
@@ -31,6 +32,7 @@ from .views.special import (
     PatternPortfolioView,
     AuthTokenView,
     PermissionsDebugView,
+    MessagesDebugView,
 )
 from .views.table import RowView, TableView
 from .renderer import json_renderer
@@ -157,6 +159,11 @@ async def favicon(scope, receive, send):
 
 
 class Datasette:
+    # Message constants:
+    INFO = 1
+    WARNING = 2
+    ERROR = 3
+
     def __init__(
         self,
         files,
@@ -424,6 +431,38 @@ class Datasette:
         # pylint: disable=no-member
         pm.hook.prepare_connection(conn=conn, database=database, datasette=self)
 
+    def add_message(self, request, message, type=INFO):
+        if not hasattr(request, "_messages"):
+            request._messages = []
+            request._messages_should_clear = False
+        request._messages.append((message, type))
+
+    def _write_messages_to_response(self, request, response):
+        if getattr(request, "_messages", None):
+            # Set those messages
+            cookie = SimpleCookie()
+            cookie["ds_messages"] = self.sign(request._messages, "messages")
+            cookie["ds_messages"]["path"] = "/"
+            # TODO: Co-exist with existing set-cookie headers
+            assert "set-cookie" not in response.headers
+            response.headers["set-cookie"] = cookie.output(header="").lstrip()
+        elif getattr(request, "_messages_should_clear", False):
+            cookie = SimpleCookie()
+            cookie["ds_messages"] = ""
+            cookie["ds_messages"]["path"] = "/"
+            # TODO: Co-exist with existing set-cookie headers
+            assert "set-cookie" not in response.headers
+            response.headers["set-cookie"] = cookie.output(header="").lstrip()
+
+    def _show_messages(self, request):
+        if getattr(request, "_messages", None):
+            request._messages_should_clear = True
+            messages = request._messages
+            request._messages = []
+            return messages
+        else:
+            return []
+
     async def permission_allowed(
         self, actor, action, resource_type=None, resource_identifier=None, default=False
     ):
@@ -809,6 +848,9 @@ class Datasette:
         add_route(
             PermissionsDebugView.as_asgi(self), r"/-/permissions$",
         )
+        add_route(
+            MessagesDebugView.as_asgi(self), r"/-/messages$",
+        )
         add_route(
             PatternPortfolioView.as_asgi(self), r"/-/patterns$",
         )

datasette/static/app.css

@@ -352,8 +352,18 @@ p.zero-results {
     color: #666;
 }
 
-.success {
+.message-info {
     padding: 1em;
     border: 1px solid green;
     background-color: #c7fbc7;
 }
+.message-warning {
+    padding: 1em;
+    border: 1px solid #ae7100;
+    background-color: #fbdda5;
+}
+.message-error {
+    padding: 1em;
+    border: 1px solid red;
+    background-color: pink;
+}

datasette/templates/base.html

@@ -17,6 +17,14 @@
 <nav class="hd">{% block nav %}{% endblock %}</nav>
 
 <div class="bd">
+{% block messages %}
+{% if show_messages %}
+    {% for message, message_type in show_messages() %}
+        <p class="message-{% if message_type == 1 %}info{% elif message_type == 2 %}warning{% elif message_type == 3 %}error{% endif %}">{{ message }}</p>
+    {% endfor %}
+{% endif %}
+{% endblock %}
+
 {% block content %}
 {% endblock %}
 </div>

datasette/templates/messages_debug.html

@@ -0,0 +1,26 @@
+{% extends "base.html" %}
+
+{% block title %}Debug messages{% endblock %}
+
+{% block content %}
+
+<h1>Debug messages</h1>
+
+<p>Set a message:</p>
+
+<form action="/-/messages" method="POST">
+    <div>
+        <input type="text" name="message" style="width: 40%">
+        <div class="select-wrapper">
+            <select name="message_type">
+                <option>INFO</option>
+                <option>WARNING</option>
+                <option>ERROR</option>
+                <option>all</option>
+            </select>
+        </div>
+        <input type="submit" value="Add message">
+    </div>
+</form>
+
+{% endblock %}

datasette/utils/asgi.py

@@ -180,9 +180,9 @@ class AsgiLifespan:
 
 
 class AsgiView:
-    def dispatch_request(self, request, *args, **kwargs):
+    async def dispatch_request(self, request, *args, **kwargs):
         handler = getattr(self, request.method.lower(), None)
-        return handler(request, *args, **kwargs)
+        return await handler(request, *args, **kwargs)
 
     @classmethod
     def as_asgi(cls, *class_args, **class_kwargs):

datasette/views/base.py

@@ -1,6 +1,7 @@
 import asyncio
 import csv
 import itertools
+from itsdangerous import BadSignature
 import json
 import re
 import time
@@ -73,6 +74,20 @@ class BaseView(AsgiView):
     def database_color(self, database):
         return "ff0000"
 
+    async def dispatch_request(self, request, *args, **kwargs):
+        # Populate request_messages if ds_messages cookie is present
+        if self.ds:
+            try:
+                request._messages = self.ds.unsign(
+                    request.cookies.get("ds_messages", ""), "messages"
+                )
+            except BadSignature:
+                pass
+        response = await super().dispatch_request(request, *args, **kwargs)
+        if self.ds:
+            self.ds._write_messages_to_response(request, response)
+        return response
+
     async def render(self, templates, request, context=None):
         context = context or {}
         template = self.ds.jinja_env.select_template(templates)
@@ -81,6 +96,7 @@ class BaseView(AsgiView):
             **{
                 "database_url": self.database_url,
                 "database_color": self.database_color,
+                "show_messages": lambda: self.ds._show_messages(request),
                 "select_templates": [
                     "{}{}".format(
                         "*" if template_name == template.name else "", template_name

datasette/views/special.py

@@ -94,3 +94,27 @@ class PermissionsDebugView(BaseView):
             request,
             {"permission_checks": reversed(self.ds._permission_checks)},
         )
+
+
+class MessagesDebugView(BaseView):
+    name = "messages_debug"
+
+    def __init__(self, datasette):
+        self.ds = datasette
+
+    async def get(self, request):
+        return await self.render(["messages_debug.html"], request)
+
+    async def post(self, request):
+        post = await request.post_vars()
+        message = post.get("message", "")
+        message_type = post.get("message_type") or "INFO"
+        assert message_type in ("INFO", "WARNING", "ERROR", "all")
+        datasette = self.ds
+        if message_type == "all":
+            datasette.add_message(request, message, datasette.INFO)
+            datasette.add_message(request, message, datasette.WARNING)
+            datasette.add_message(request, message, datasette.ERROR)
+        else:
+            datasette.add_message(request, message, getattr(datasette, message_type))
+        return Response.redirect("/")

docs/internals.rst

@@ -214,6 +214,24 @@ This method returns a signed string, which can be decoded and verified using :re
 
 Returns the original, decoded object that was passed to :ref:`datasette_sign`. If the signature is not valid this raises a ``itsdangerous.BadSignature`` exception.
 
+.. _datasette_add_message:
+
+.add_message(request, message, message_type=datasette.INFO)
+-----------------------------------------------------------
+
+``request`` - Request
+    The current Request object
+
+``message`` - string
+    The message string
+
+``message_type`` - constant, optional
+    The message type - ``datasette.INFO``, ``datasette.WARNING`` or ``datasette.ERROR``
+
+Datasette's flash messaging mechanism allows you to add a message that will be displayed to the user on the next page that they visit. Messages are persisted in a ``ds_messages`` cookie. This method adds a message to that cookie.
+
+You can try out these messages (including the different visual styling of the three message types) using the ``/-/messages`` debugging tool.
+
 .. _internals_database:
 
 Database class

docs/introspection.rst

@@ -166,3 +166,11 @@ Shows the currently authenticated actor. Useful for debugging Datasette authenti
             "username": "some-user"
         }
     }
+
+
+.. _MessagesDebugView:
+
+/-/messages
+-----------
+
+The debug tool at ``/-/messages`` can be used to set flash messages to try out that feature. See :ref:`datasette_add_message` for details of this feature.

tests/fixtures.py

@@ -29,6 +29,12 @@ class TestResponse:
         self.headers = headers
         self.body = body
 
+    @property
+    def cookies(self):
+        cookie = SimpleCookie()
+        cookie.load(self.headers.get("set-cookie") or "")
+        return {key: value.value for key, value in cookie.items()}
+
     @property
     def json(self):
         return json.loads(self.text)

tests/plugins/messages_output_renderer.py

@@ -0,0 +1,21 @@
+from datasette import hookimpl
+
+
+def render_message_debug(datasette, request):
+    if request.args.get("add_msg"):
+        msg_type = request.args.get("type", "INFO")
+        datasette.add_message(
+            request, request.args["add_msg"], getattr(datasette, msg_type)
+        )
+    return {"body": "Hello from message debug"}
+
+
+@hookimpl
+def register_output_renderer(datasette):
+    return [
+        {
+            "extension": "message",
+            "render": render_message_debug,
+            "can_render": lambda: False,
+        }
+    ]

tests/test_api.py

@@ -1262,6 +1262,7 @@ def test_plugins_json(app_client):
     expected = [
         {"name": name, "static": False, "templates": False, "version": None}
         for name in (
+            "messages_output_renderer.py",
             "my_plugin.py",
             "my_plugin_2.py",
             "register_output_renderer.py",

tests/test_auth.py

@@ -9,11 +9,7 @@ def test_auth_token(app_client):
     response = app_client.get(path, allow_redirects=False,)
     assert 302 == response.status
     assert "/" == response.headers["Location"]
-    set_cookie = response.headers["set-cookie"]
+    assert {"id": "root"} == app_client.ds.unsign(response.cookies["ds_actor"], "actor")
-    assert set_cookie.endswith("; Path=/")
-    assert set_cookie.startswith("ds_actor=")
-    cookie_value = set_cookie.split("ds_actor=")[1].split("; Path=/")[0]
-    assert {"id": "root"} == app_client.ds.unsign(cookie_value, "actor")
     # Check that a second with same token fails
     assert app_client.ds._root_token is None
     assert 403 == app_client.get(path, allow_redirects=False,).status

tests/test_messages.py

@@ -0,0 +1,28 @@
+from .fixtures import app_client
+import pytest
+
+
+@pytest.mark.parametrize(
+    "qs,expected",
+    [
+        ("add_msg=added-message", [["added-message", 1]]),
+        ("add_msg=added-warning&type=WARNING", [["added-warning", 2]]),
+        ("add_msg=added-error&type=ERROR", [["added-error", 3]]),
+    ],
+)
+def test_add_message_sets_cookie(app_client, qs, expected):
+    response = app_client.get("/fixtures.message?{}".format(qs))
+    signed = response.cookies["ds_messages"]
+    decoded = app_client.ds.unsign(signed, "messages")
+    assert expected == decoded
+
+
+def test_messages_are_displayed_and_cleared(app_client):
+    # First set the message cookie
+    set_msg_response = app_client.get("/fixtures.message?add_msg=xmessagex")
+    # Now access a page that displays messages
+    response = app_client.get("/", cookies=set_msg_response.cookies)
+    # Messages should be in that HTML
+    assert "xmessagex" in response.text
+    # Cookie should have been set that clears messages
+    assert "" == response.cookies["ds_messages"]