From b52171db1e97e2be1ff2dc505ccf29107288b27b Mon Sep 17 00:00:00 2001
From: Simon Willison <swillison@gmail.com>
Date: Wed, 18 Apr 2018 22:50:27 -0700
Subject: [PATCH] Plugins can now bundle custom templates, closes #224

Refs #14
---
 datasette/app.py   | 27 +++++++++++++++++----------
 datasette/utils.py |  4 ++++
 docs/plugins.rst   | 15 +++++++++++++++
 tests/test_api.py  |  6 +++++-
 4 files changed, 41 insertions(+), 11 deletions(-)

diff --git a/datasette/app.py b/datasette/app.py
index cc3a9c08..79ce012e 100644
--- a/datasette/app.py
+++ b/datasette/app.py
@@ -1303,16 +1303,22 @@ class Datasette:
     def app(self):
         app = Sanic(__name__)
         default_templates = str(app_root / 'datasette' / 'templates')
+        template_paths = []
         if self.template_dir:
-            template_loader = ChoiceLoader([
-                FileSystemLoader([self.template_dir, default_templates]),
-                # Support {% extends "default:table.html" %}:
-                PrefixLoader({
-                    'default': FileSystemLoader(default_templates),
-                }, delimiter=':')
-            ])
-        else:
-            template_loader = FileSystemLoader(default_templates)
+            template_paths.append(self.template_dir)
+        template_paths.extend([
+            plugin['templates_path']
+            for plugin in get_plugins(pm)
+            if plugin['templates_path']
+        ])
+        template_paths.append(default_templates)
+        template_loader = ChoiceLoader([
+            FileSystemLoader(template_paths),
+            # Support {% extends "default:table.html" %}:
+            PrefixLoader({
+                'default': FileSystemLoader(default_templates),
+            }, delimiter=':')
+        ])
         self.jinja_env = Environment(
             loader=template_loader,
             autoescape=True,
@@ -1344,7 +1350,8 @@ class Datasette:
         app.add_route(
             JsonDataView.as_view(self, 'plugins.json', lambda: [{
                 'name': p['name'],
-                'static': p['static_path'] is not None
+                'static': p['static_path'] is not None,
+                'templates': p['templates_path'] is not None,
             } for p in get_plugins(pm)]),
             '/-/plugins<as_json:(\.json)?$>'
         )
diff --git a/datasette/utils.py b/datasette/utils.py
index 3ef045fb..863079bf 100644
--- a/datasette/utils.py
+++ b/datasette/utils.py
@@ -690,14 +690,18 @@ def get_plugins(pm):
     plugins = []
     for plugin in pm.get_plugins():
         static_path = None
+        templates_path = None
         try:
             if pkg_resources.resource_isdir(plugin.__name__, 'static'):
                 static_path = pkg_resources.resource_filename(plugin.__name__, 'static')
+            if pkg_resources.resource_isdir(plugin.__name__, 'templates'):
+                templates_path = pkg_resources.resource_filename(plugin.__name__, 'templates')
         except (KeyError, ImportError):
             # Caused by --plugins_dir= plugins - KeyError/ImportError thrown in Py3.5
             pass
         plugins.append({
             'name': plugin.__name__,
             'static_path': static_path,
+            'templates_path': templates_path,
         })
     return plugins
diff --git a/docs/plugins.rst b/docs/plugins.rst
index 40e73436..b83527ff 100644
--- a/docs/plugins.rst
+++ b/docs/plugins.rst
@@ -132,6 +132,21 @@ configure itself to serve those static assets from the following path::
 See `the datasette-plugin-demos repository <https://github.com/simonw/datasette-plugin-demos/tree/0ccf9e6189e923046047acd7878d1d19a2cccbb1>`_
 for an example of how to create a package that includes a static folder.
 
+Custom templates
+----------------
+
+If your plugin has a ``templates/`` directory, Datasette will attempt to load
+templates from that directory before it uses its own default templates.
+
+The priority order for template loading is:
+
+* templates from the ``--template-dir`` argument, if specified
+* templates from the ``templates/`` directory in any installed plugins
+* default templates that ship with Datasette
+
+See :ref:`customization` for more details on how to write custom templates,
+including which filenames to use to customize which parts of the Datasette UI.
+
 Plugin hooks
 ------------
 
diff --git a/tests/test_api.py b/tests/test_api.py
index e1db8c46..4f1ed6f2 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -656,4 +656,8 @@ def test_plugins_json(app_client):
     # This will include any plugins that have been installed into the
     # current virtual environment, so we only check for the presence of
     # the one we know will definitely be There
-    assert {'name': 'my_plugin.py', 'static': False} in response.json
+    assert {
+        'name': 'my_plugin.py',
+        'static': False,
+        'templates': False
+    } in response.json