django/tests/migrations/test_graph.py

from django.db.migrations.exceptions import (
    CircularDependencyError, NodeNotFoundError,
)
from django.db.migrations.graph import DummyNode, MigrationGraph, Node
from django.test import SimpleTestCase


class GraphTests(SimpleTestCase):
    """
    Tests the digraph structure.
    """

    def test_simple_graph(self):
        """
        Tests a basic dependency graph:

        app_a:  0001 <-- 0002 <--- 0003 <-- 0004
                                 /
        app_b:  0001 <-- 0002 <-/
        """
        # Build graph
        graph = MigrationGraph()
        graph.add_node(("app_a", "0001"), None)
        graph.add_node(("app_a", "0002"), None)
        graph.add_node(("app_a", "0003"), None)
        graph.add_node(("app_a", "0004"), None)
        graph.add_node(("app_b", "0001"), None)
        graph.add_node(("app_b", "0002"), None)
        graph.add_dependency("app_a.0004", ("app_a", "0004"), ("app_a", "0003"))
        graph.add_dependency("app_a.0003", ("app_a", "0003"), ("app_a", "0002"))
        graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))
        graph.add_dependency("app_a.0003", ("app_a", "0003"), ("app_b", "0002"))
        graph.add_dependency("app_b.0002", ("app_b", "0002"), ("app_b", "0001"))
        # Test root migration case
        self.assertEqual(
            graph.forwards_plan(("app_a", "0001")),
            [('app_a', '0001')],
        )
        # Test branch B only
        self.assertEqual(
            graph.forwards_plan(("app_b", "0002")),
            [("app_b", "0001"), ("app_b", "0002")],
        )
        # Test whole graph
        self.assertEqual(
            graph.forwards_plan(("app_a", "0004")),
            [
                ('app_b', '0001'), ('app_b', '0002'), ('app_a', '0001'),
                ('app_a', '0002'), ('app_a', '0003'), ('app_a', '0004'),
            ],
        )
        # Test reverse to b:0002
        self.assertEqual(
            graph.backwards_plan(("app_b", "0002")),
            [('app_a', '0004'), ('app_a', '0003'), ('app_b', '0002')],
        )
        # Test roots and leaves
        self.assertEqual(
            graph.root_nodes(),
            [('app_a', '0001'), ('app_b', '0001')],
        )
        self.assertEqual(
            graph.leaf_nodes(),
            [('app_a', '0004'), ('app_b', '0002')],
        )

    def test_complex_graph(self):
        r"""
        Tests a complex dependency graph:

        app_a:  0001 <-- 0002 <--- 0003 <-- 0004
                      \        \ /         /
        app_b:  0001 <-\ 0002 <-X         /
                      \          \       /
        app_c:         \ 0001 <-- 0002 <-
        """
        # Build graph
        graph = MigrationGraph()
        graph.add_node(("app_a", "0001"), None)
        graph.add_node(("app_a", "0002"), None)
        graph.add_node(("app_a", "0003"), None)
        graph.add_node(("app_a", "0004"), None)
        graph.add_node(("app_b", "0001"), None)
        graph.add_node(("app_b", "0002"), None)
        graph.add_node(("app_c", "0001"), None)
        graph.add_node(("app_c", "0002"), None)
        graph.add_dependency("app_a.0004", ("app_a", "0004"), ("app_a", "0003"))
        graph.add_dependency("app_a.0003", ("app_a", "0003"), ("app_a", "0002"))
        graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))
        graph.add_dependency("app_a.0003", ("app_a", "0003"), ("app_b", "0002"))
        graph.add_dependency("app_b.0002", ("app_b", "0002"), ("app_b", "0001"))
        graph.add_dependency("app_a.0004", ("app_a", "0004"), ("app_c", "0002"))
        graph.add_dependency("app_c.0002", ("app_c", "0002"), ("app_c", "0001"))
        graph.add_dependency("app_c.0001", ("app_c", "0001"), ("app_b", "0001"))
        graph.add_dependency("app_c.0002", ("app_c", "0002"), ("app_a", "0002"))
        # Test branch C only
        self.assertEqual(
            graph.forwards_plan(("app_c", "0002")),
            [('app_b', '0001'), ('app_c', '0001'), ('app_a', '0001'), ('app_a', '0002'), ('app_c', '0002')],
        )
        # Test whole graph
        self.assertEqual(
            graph.forwards_plan(("app_a", "0004")),
            [
                ('app_b', '0001'), ('app_c', '0001'), ('app_a', '0001'),
                ('app_a', '0002'), ('app_c', '0002'), ('app_b', '0002'),
                ('app_a', '0003'), ('app_a', '0004'),
            ],
        )
        # Test reverse to b:0001
        self.assertEqual(
            graph.backwards_plan(("app_b", "0001")),
            [
                ('app_a', '0004'), ('app_c', '0002'), ('app_c', '0001'),
                ('app_a', '0003'), ('app_b', '0002'), ('app_b', '0001'),
            ],
        )
        # Test roots and leaves
        self.assertEqual(
            graph.root_nodes(),
            [('app_a', '0001'), ('app_b', '0001'), ('app_c', '0001')],
        )
        self.assertEqual(
            graph.leaf_nodes(),
            [('app_a', '0004'), ('app_b', '0002'), ('app_c', '0002')],
        )

    def test_circular_graph(self):
        """
        Tests a circular dependency graph.
        """
        # Build graph
        graph = MigrationGraph()
        graph.add_node(("app_a", "0001"), None)
        graph.add_node(("app_a", "0002"), None)
        graph.add_node(("app_a", "0003"), None)
        graph.add_node(("app_b", "0001"), None)
        graph.add_node(("app_b", "0002"), None)
        graph.add_dependency("app_a.0003", ("app_a", "0003"), ("app_a", "0002"))
        graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))
        graph.add_dependency("app_a.0001", ("app_a", "0001"), ("app_b", "0002"))
        graph.add_dependency("app_b.0002", ("app_b", "0002"), ("app_b", "0001"))
        graph.add_dependency("app_b.0001", ("app_b", "0001"), ("app_a", "0003"))
        # Test whole graph
        with self.assertRaises(CircularDependencyError):
            graph.ensure_not_cyclic()

    def test_circular_graph_2(self):
        graph = MigrationGraph()
        graph.add_node(('A', '0001'), None)
        graph.add_node(('C', '0001'), None)
        graph.add_node(('B', '0001'), None)
        graph.add_dependency('A.0001', ('A', '0001'), ('B', '0001'))
        graph.add_dependency('B.0001', ('B', '0001'), ('A', '0001'))
        graph.add_dependency('C.0001', ('C', '0001'), ('B', '0001'))

        with self.assertRaises(CircularDependencyError):
            graph.ensure_not_cyclic()

    def test_iterative_dfs(self):
        graph = MigrationGraph()
        root = ("app_a", "1")
        graph.add_node(root, None)
        expected = [root]
        for i in range(2, 750):
            parent = ("app_a", str(i - 1))
            child = ("app_a", str(i))
            graph.add_node(child, None)
            graph.add_dependency(str(i), child, parent)
            expected.append(child)
        leaf = expected[-1]

        forwards_plan = graph.forwards_plan(leaf)
        self.assertEqual(expected, forwards_plan)

        backwards_plan = graph.backwards_plan(root)
        self.assertEqual(expected[::-1], backwards_plan)

    def test_iterative_dfs_complexity(self):
        """
        In a graph with merge migrations, iterative_dfs() traverses each node
        only once even if there are multiple paths leading to it.
        """
        n = 50
        graph = MigrationGraph()
        for i in range(1, n + 1):
            graph.add_node(('app_a', str(i)), None)
            graph.add_node(('app_b', str(i)), None)
            graph.add_node(('app_c', str(i)), None)
        for i in range(1, n):
            graph.add_dependency(None, ('app_b', str(i)), ('app_a', str(i)))
            graph.add_dependency(None, ('app_c', str(i)), ('app_a', str(i)))
            graph.add_dependency(None, ('app_a', str(i + 1)), ('app_b', str(i)))
            graph.add_dependency(None, ('app_a', str(i + 1)), ('app_c', str(i)))
        plan = graph.forwards_plan(('app_a', str(n)))
        expected = [
            (app, str(i))
            for i in range(1, n)
            for app in ['app_a', 'app_c', 'app_b']
        ] + [('app_a', str(n))]
        self.assertEqual(plan, expected)

    def test_plan_invalid_node(self):
        """
        Tests for forwards/backwards_plan of nonexistent node.
        """
        graph = MigrationGraph()
        message = "Node ('app_b', '0001') not a valid node"

        with self.assertRaisesMessage(NodeNotFoundError, message):
            graph.forwards_plan(("app_b", "0001"))

        with self.assertRaisesMessage(NodeNotFoundError, message):
            graph.backwards_plan(("app_b", "0001"))

    def test_missing_parent_nodes(self):
        """
        Tests for missing parent nodes.
        """
        # Build graph
        graph = MigrationGraph()
        graph.add_node(("app_a", "0001"), None)
        graph.add_node(("app_a", "0002"), None)
        graph.add_node(("app_a", "0003"), None)
        graph.add_node(("app_b", "0001"), None)
        graph.add_dependency("app_a.0003", ("app_a", "0003"), ("app_a", "0002"))
        graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))
        msg = "Migration app_a.0001 dependencies reference nonexistent parent node ('app_b', '0002')"
        with self.assertRaisesMessage(NodeNotFoundError, msg):
            graph.add_dependency("app_a.0001", ("app_a", "0001"), ("app_b", "0002"))

    def test_missing_child_nodes(self):
        """
        Tests for missing child nodes.
        """
        # Build graph
        graph = MigrationGraph()
        graph.add_node(("app_a", "0001"), None)
        msg = "Migration app_a.0002 dependencies reference nonexistent child node ('app_a', '0002')"
        with self.assertRaisesMessage(NodeNotFoundError, msg):
            graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))

    def test_validate_consistency_missing_parent(self):
        graph = MigrationGraph()
        graph.add_node(("app_a", "0001"), None)
        graph.add_dependency("app_a.0001", ("app_a", "0001"), ("app_b", "0002"), skip_validation=True)
        msg = "Migration app_a.0001 dependencies reference nonexistent parent node ('app_b', '0002')"
        with self.assertRaisesMessage(NodeNotFoundError, msg):
            graph.validate_consistency()

    def test_validate_consistency_missing_child(self):
        graph = MigrationGraph()
        graph.add_node(("app_b", "0002"), None)
        graph.add_dependency("app_b.0002", ("app_a", "0001"), ("app_b", "0002"), skip_validation=True)
        msg = "Migration app_b.0002 dependencies reference nonexistent child node ('app_a', '0001')"
        with self.assertRaisesMessage(NodeNotFoundError, msg):
            graph.validate_consistency()

    def test_validate_consistency_no_error(self):
        graph = MigrationGraph()
        graph.add_node(("app_a", "0001"), None)
        graph.add_node(("app_b", "0002"), None)
        graph.add_dependency("app_a.0001", ("app_a", "0001"), ("app_b", "0002"), skip_validation=True)
        graph.validate_consistency()

    def test_validate_consistency_dummy(self):
        """
        validate_consistency() raises an error if there's an isolated dummy
        node.
        """
        msg = "app_a.0001 (req'd by app_b.0002) is missing!"
        graph = MigrationGraph()
        graph.add_dummy_node(
            key=("app_a", "0001"),
            origin="app_b.0002",
            error_message=msg
        )
        with self.assertRaisesMessage(NodeNotFoundError, msg):
            graph.validate_consistency()

    def test_remove_replaced_nodes(self):
        """
        Replaced nodes are properly removed and dependencies remapped.
        """
        # Add some dummy nodes to be replaced.
        graph = MigrationGraph()
        graph.add_dummy_node(key=("app_a", "0001"), origin="app_a.0002", error_message="BAD!")
        graph.add_dummy_node(key=("app_a", "0002"), origin="app_b.0001", error_message="BAD!")
        graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"), skip_validation=True)
        # Add some normal parent and child nodes to test dependency remapping.
        graph.add_node(("app_c", "0001"), None)
        graph.add_node(("app_b", "0001"), None)
        graph.add_dependency("app_a.0001", ("app_a", "0001"), ("app_c", "0001"), skip_validation=True)
        graph.add_dependency("app_b.0001", ("app_b", "0001"), ("app_a", "0002"), skip_validation=True)
        # Try replacing before replacement node exists.
        msg = (
            "Unable to find replacement node ('app_a', '0001_squashed_0002'). It was either"
            " never added to the migration graph, or has been removed."
        )
        with self.assertRaisesMessage(NodeNotFoundError, msg):
            graph.remove_replaced_nodes(
                replacement=("app_a", "0001_squashed_0002"),
                replaced=[("app_a", "0001"), ("app_a", "0002")]
            )
        graph.add_node(("app_a", "0001_squashed_0002"), None)
        # Ensure `validate_consistency()` still raises an error at this stage.
        with self.assertRaisesMessage(NodeNotFoundError, "BAD!"):
            graph.validate_consistency()
        # Remove the dummy nodes.
        graph.remove_replaced_nodes(
            replacement=("app_a", "0001_squashed_0002"),
            replaced=[("app_a", "0001"), ("app_a", "0002")]
        )
        # Ensure graph is now consistent and dependencies have been remapped
        graph.validate_consistency()
        parent_node = graph.node_map[("app_c", "0001")]
        replacement_node = graph.node_map[("app_a", "0001_squashed_0002")]
        child_node = graph.node_map[("app_b", "0001")]
        self.assertIn(parent_node, replacement_node.parents)
        self.assertIn(replacement_node, parent_node.children)
        self.assertIn(child_node, replacement_node.children)
        self.assertIn(replacement_node, child_node.parents)

    def test_remove_replacement_node(self):
        """
        A replacement node is properly removed and child dependencies remapped.
        We assume parent dependencies are already correct.
        """
        # Add some dummy nodes to be replaced.
        graph = MigrationGraph()
        graph.add_node(("app_a", "0001"), None)
        graph.add_node(("app_a", "0002"), None)
        graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))
        # Try removing replacement node before replacement node exists.
        msg = (
            "Unable to remove replacement node ('app_a', '0001_squashed_0002'). It was"
            " either never added to the migration graph, or has been removed already."
        )
        with self.assertRaisesMessage(NodeNotFoundError, msg):
            graph.remove_replacement_node(
                replacement=("app_a", "0001_squashed_0002"),
                replaced=[("app_a", "0001"), ("app_a", "0002")]
            )
        graph.add_node(("app_a", "0001_squashed_0002"), None)
        # Add a child node to test dependency remapping.
        graph.add_node(("app_b", "0001"), None)
        graph.add_dependency("app_b.0001", ("app_b", "0001"), ("app_a", "0001_squashed_0002"))
        # Remove the replacement node.
        graph.remove_replacement_node(
            replacement=("app_a", "0001_squashed_0002"),
            replaced=[("app_a", "0001"), ("app_a", "0002")]
        )
        # Ensure graph is consistent and child dependency has been remapped
        graph.validate_consistency()
        replaced_node = graph.node_map[("app_a", "0002")]
        child_node = graph.node_map[("app_b", "0001")]
        self.assertIn(child_node, replaced_node.children)
        self.assertIn(replaced_node, child_node.parents)
        # Ensure child dependency hasn't also gotten remapped to the other replaced node.
        other_replaced_node = graph.node_map[("app_a", "0001")]
        self.assertNotIn(child_node, other_replaced_node.children)
        self.assertNotIn(other_replaced_node, child_node.parents)

    def test_infinite_loop(self):
        """
        Tests a complex dependency graph:

        app_a:        0001 <-
                             \
        app_b:        0001 <- x 0002 <-
                       /               \
        app_c:   0001<-  <------------- x 0002

        And apply squashing on app_c.
        """
        graph = MigrationGraph()

        graph.add_node(("app_a", "0001"), None)
        graph.add_node(("app_b", "0001"), None)
        graph.add_node(("app_b", "0002"), None)
        graph.add_node(("app_c", "0001_squashed_0002"), None)

        graph.add_dependency("app_b.0001", ("app_b", "0001"), ("app_c", "0001_squashed_0002"))
        graph.add_dependency("app_b.0002", ("app_b", "0002"), ("app_a", "0001"))
        graph.add_dependency("app_b.0002", ("app_b", "0002"), ("app_b", "0001"))
        graph.add_dependency("app_c.0001_squashed_0002", ("app_c", "0001_squashed_0002"), ("app_b", "0002"))

        with self.assertRaises(CircularDependencyError):
            graph.ensure_not_cyclic()

    def test_stringify(self):
        graph = MigrationGraph()
        self.assertEqual(str(graph), "Graph: 0 nodes, 0 edges")

        graph.add_node(("app_a", "0001"), None)
        graph.add_node(("app_a", "0002"), None)
        graph.add_node(("app_a", "0003"), None)
        graph.add_node(("app_b", "0001"), None)
        graph.add_node(("app_b", "0002"), None)
        graph.add_dependency("app_a.0002", ("app_a", "0002"), ("app_a", "0001"))
        graph.add_dependency("app_a.0003", ("app_a", "0003"), ("app_a", "0002"))
        graph.add_dependency("app_a.0003", ("app_a", "0003"), ("app_b", "0002"))

        self.assertEqual(str(graph), "Graph: 5 nodes, 3 edges")
        self.assertEqual(repr(graph), "<MigrationGraph: nodes=5, edges=3>")


class NodeTests(SimpleTestCase):
    def test_node_repr(self):
        node = Node(('app_a', '0001'))
        self.assertEqual(repr(node), "<Node: ('app_a', '0001')>")

    def test_dummynode_repr(self):
        node = DummyNode(
            key=('app_a', '0001'),
            origin='app_a.0001',
            error_message='x is missing',
        )
        self.assertEqual(repr(node), "<DummyNode: ('app_a', '0001')>")