Generic PATCH handler class.

A class-based approach is easier to extend than the function-based approach
used in the nodes. That one is still there, though -- might look at it
at a later time. This handler is primarily for Flamenco.

tests/test_api/test_patch_handler.py

@@ -0,0 +1,89 @@
+from pillar.tests import AbstractPillarTest
+
+
+class PatchHandlerTest(AbstractPillarTest):
+    def setUp(self, **kwargs):
+        super().setUp(**kwargs)
+        import flask
+        from pillar.api import patch_handler
+
+        # Create a patch handler and register it.
+        class BogusPatchHandler(patch_handler.AbstractPatchHandler):
+            item_name = 'gremlin'
+
+            def patch_test_echo(self, op: str, patch: dict):
+                return flask.jsonify({'echo': patch['echo']})
+
+            def patch_test_empty(self, op: str, patch: dict):
+                return None
+
+        blueprint = flask.Blueprint('test_patch_handler', __name__)
+        self.patch_handler = BogusPatchHandler(blueprint)
+
+        self.app.register_api_blueprint(blueprint, url_prefix='/test')
+
+        # Patching always requires a logged-in user.
+        self.user_id = self.create_user(token='user-token')
+
+    def test_patch_anonymous(self):
+        import bson
+
+        oid = bson.ObjectId()
+        self.patch('/api/test/%s' % oid, expected_status=403)
+
+    def test_patch_without_json(self):
+        import bson
+
+        oid = bson.ObjectId()
+        self.patch('/api/test/%s' % oid, auth_token='user-token', expected_status=400)
+
+    def test_patch_no_operation(self):
+        import bson
+
+        oid = bson.ObjectId()
+        self.patch('/api/test/%s' % oid, auth_token='user-token',
+                   json={'je': 'moeder'},
+                   expected_status=400)
+
+    def test_patch_invalid_operation(self):
+        import bson
+
+        oid = bson.ObjectId()
+        self.patch('/api/test/%s' % oid, auth_token='user-token',
+                   json={'op': 'snowcrash'},
+                   expected_status=400)
+
+    def test_patch_happy(self):
+        import bson
+
+        oid = bson.ObjectId()
+        resp = self.patch('/api/test/%s' % oid, auth_token='user-token',
+                          json={'op': 'test-echo',
+                                'echo': '¡Thith ith Špahtah!'})
+        self.assertEqual({'echo': '¡Thith ith Špahtah!'}, resp.json())
+
+    def test_patch_empty_response(self):
+        import bson
+
+        oid = bson.ObjectId()
+        resp = self.patch('/api/test/%s' % oid, auth_token='user-token',
+                          json={'op': 'test-empty',
+                                'echo': '¡Thith ith Špahtah!'},
+                          expected_status=204)
+        self.assertEqual(b'', resp.data)
+
+
+class PatchHandlerCreationTest(AbstractPillarTest):
+    def test_without_route(self):
+        from pillar.api import patch_handler
+
+        with self.assertRaises(ValueError):
+            class BogusPatchHandler(patch_handler.AbstractPatchHandler):
+                route = ''
+
+    def test_without_item_name(self):
+        from pillar.api import patch_handler
+
+        with self.assertRaises(ValueError):
+            class BogusPatchHandler(patch_handler.AbstractPatchHandler):
+                pass