Refactor the API ordering to accept multiple order keyword arguments of the same direction

This also improves how a column is determined to be valid for ordering.

README.rst

@@ -280,9 +280,9 @@ module builds are displayed. These parameters are:
   value defaults to 1.
 - ``per_page`` - Specifies how many items per page should be displayed
   (e.g. ``per_page=20``). This value defaults to 10.
-- ``order_by`` - a database column to order the API by in ascending order.
-- ``order_desc_by`` - a database column to order the API by in descending order. This defaults to
-  ``id``.
+- ``order_by`` - a database column to order the API by in ascending order. Multiple can be provided.
+- ``order_desc_by`` - a database column to order the API by in descending order. Multiple can be
+  provided. This defaults to ``id``.
 
 An example of querying the "module-builds" resource with the "per_page" and the "page"
 parameters::

module_build_service/utils/views.py

@@ -30,6 +30,7 @@ from datetime import datetime
 from flask import request, url_for, Response
 from sqlalchemy.sql.sqltypes import Boolean as sqlalchemy_boolean
 from sqlalchemy.orm import aliased
+import sqlalchemy
 
 from module_build_service import models, api_version, conf
 from module_build_service.errors import ValidationError, NotFound
@@ -96,30 +97,44 @@ def pagination_metadata(p_query, api_version, request_args):
 
 def _add_order_by_clause(flask_request, query, column_source):
     """
-    Orders the given SQLAlchemy query based on the GET arguments provided
+    Orders the given SQLAlchemy query based on the GET arguments provided.
+
     :param flask_request: a Flask request object
     :param query: a SQLAlchemy query object
     :param column_source: a SQLAlchemy database model
     :return: a SQLAlchemy query object
     """
-    colname = "id"
+    order_by = flask_request.args.getlist('order_by')
+    order_desc_by = flask_request.args.getlist('order_desc_by')
+    # Default to ordering by ID in descending order
     descending = True
-    order_desc_by = flask_request.args.get("order_desc_by", None)
-    if order_desc_by:
-        colname = order_desc_by
-    else:
-        order_by = flask_request.args.get("order_by", None)
-        if order_by:
-            colname = order_by
-            descending = False
+    requested_order = ['id']
 
-    column = getattr(column_source, colname, None)
-    if not column:
-        raise ValidationError('An invalid order_by or order_desc_by key '
-                              'was supplied')
-    if descending:
-        column = column.desc()
-    return query.order_by(column)
+    if order_by and order_desc_by:
+        raise ValidationError('You may not specify both order_by and order_desc_by')
+    elif order_by:
+        descending = False
+        requested_order = order_by
+    elif order_desc_by:
+        descending = True
+        requested_order = order_desc_by
+
+    column_dict = dict(column_source.__table__.columns)
+    order_args = []
+    for column_name in requested_order:
+        if column_name not in column_dict:
+            raise ValidationError(
+                'An invalid ordering key of "{}" was supplied'.format(column_name))
+        column = column_dict[column_name]
+        # If the version column is provided, cast it as an integer so the sorting is correct
+        if column_name == 'version':
+            column = sqlalchemy.cast(column, sqlalchemy.BigInteger)
+        if descending:
+            column = column.desc()
+
+        order_args.append(column)
+
+    return query.order_by(*order_args)
 
 
 def str_to_bool(value):

tests/test_views/test_views.py

@@ -663,6 +663,20 @@ class TestViews:
         assert items[0]['name'] == 'candy'
         assert items[1]['name'] == 'nginx'
 
+    def test_query_builds_order_by_multiple(self):
+        init_data(data_size=1, multiple_stream_versions=True)
+        platform_f28 = db.session.query(module_build_service.models.ModuleBuild).get(1)
+        platform_f28.version = '150'
+        db.session.add(platform_f28)
+        db.session.commit()
+        rv = self.client.get(
+            '/module-build-service/1/module-builds/?order_desc_by=stream_version'
+            '&order_desc_by=version')
+        items = json.loads(rv.data)['items']
+        expected_ids = [8, 6, 4, 1, 2, 12, 3, 5, 7, 9]
+        actual_ids = [item['id'] for item in items]
+        assert actual_ids == expected_ids
+
     def test_query_builds_order_desc_by(self):
         rv = self.client.get('/module-build-service/1/module-builds/?'
                              'per_page=10&order_desc_by=id')
@@ -685,23 +699,28 @@ class TestViews:
 
     def test_query_builds_order_by_order_desc_by(self):
         """
-        Test that when both order_by and order_desc_by is set,
-        we prefer order_desc_by.
+        Test that when both order_by and order_desc_by are set, an error is returned.
         """
         rv = self.client.get('/module-build-service/1/module-builds/?'
                              'per_page=10&order_desc_by=id&order_by=name')
-        items = json.loads(rv.data)['items']
-        # Check that the id is items[0]["id"], items[0]["id"] - 1, ...
-        for idx, item in enumerate(items):
-            assert item["id"] == items[0]["id"] - idx
+        error = json.loads(rv.data)
+        expected = {
+            'error': 'Bad Request',
+            'message': 'You may not specify both order_by and order_desc_by',
+            'status': 400
+        }
+        assert error == expected
 
     def test_query_builds_order_by_wrong_key(self):
         rv = self.client.get('/module-build-service/1/module-builds/?'
                              'per_page=10&order_by=unknown')
-        data = json.loads(rv.data)
-        assert data['status'] == 400
-        assert data['error'] == 'Bad Request'
-        assert data['message'] == 'An invalid order_by or order_desc_by key was supplied'
+        error = json.loads(rv.data)
+        expected = {
+            'error': 'Bad Request',
+            'message': 'An invalid ordering key of "unknown" was supplied',
+            'status': 400,
+        }
+        assert error == expected
 
     def test_query_base_module_br_filters(self):
         reuse_component_init_data()