issue2551328/issue2551264 unneeded next link and total_count incorrect Fix: issue2551328 - REST results show next link if number of results is a multiple of page size. (Found by members of team 3 in the UMass-Boston CS682 Spring 2024 class.) issue2551264 - REST X-Total-Count header and @total_size count incorrect when paginated These issues arose because we retrieved the exact number of rows from the database as requested by the user using the @page_size parameter. With this changeset, we retrieve up to 10 million + 1 rows from the database. If the total number of rows exceeds 10 million, we set the total_count indicators to -1 as an invalid size. (The max number of requested rows (default 10 million +1) can be modified by the admin through interfaces.py.) By retrieving more data than necessary, we can calculate the total count by adding @page_index*@page_size to the number of rows returned by the query. Furthermore, since we return more than @page_size rows, we can determine the existence of a row at @page_size+1 and use that information to determine if a next link should be provided. Previously, a next link was returned if @page_size rows were retrieved. This change does not guarantee that the user will get @page_size rows returned. Access policy filtering occurs after the rows are returned, and discards rows inaccessible by the user. Using the current @page_index/@page_size it would be difficult to have the roundup code refetch data and make sure that a full @page_size set of rows is returned. E.G. @page_size=100 and 5 of them are dropped due to access restrictions. We then fetch 10 items and add items 1-4 and 6 (5 is inaccessible). There is no way to calculate the new database offset at: @page_index*@page_size + 6 from the URL. We would need to add an @page_offset=6 or something. This could work since the client isn't adding 1 to @page_index to get the next page. Thanks to HATEOAS, the client just uses the 'next' url. But I am not going to cross that bridge without a concrete use case. This can also be handled client side by merging a short response with the next response and re-paginating client side. Also added extra index markers to the docs to highlight use of interfaces.py.

#
# Copyright (C) 2020 John Rouillard
# All rights reserved.
# For license terms see the file COPYING.txt.
#

from __future__ import print_function
import unittest, os, shutil, errno, sys, difflib

from roundup import instance
from roundup.instance import TrackerError

try:
  # python2
  import pathlib2 as pathlib
except ImportError:
  # python3
  import pathlib

from . import db_test_base

class InstanceTest(unittest.TestCase):

    backend = 'anydbm'

    def setUp(self):
        self.dirname = '_test_instance'
        # set up and open a tracker
        self.instance = db_test_base.setupTracker(self.dirname, self.backend)

        # open the database
        self.db = self.instance.open('admin')

        self.db.commit()
        self.db.close()

    def tearDown(self):
        if self.db:
            self.db.close()
        try:
            shutil.rmtree(self.dirname)
        except OSError as error:
            if error.errno not in (errno.ENOENT, errno.ESRCH): raise


    def testOpenOldStyle(self):
        pathlib.Path(os.path.join(self.dirname, "dbinit.py")).touch()
        # no longer support old style tracker configs
        self.assertRaises(TrackerError, instance.open, self.dirname)