[2.2.x] Refs #30179 -- Moved topological sort functions to django.utils.

Backport of e04209e181c99ac16ca769d115ac640015a83757 from master.

2 files changed, 1 insertions, 34 deletions

diff --git a/django/db/migrations/autodetector.py b/django/db/migrations/autodetector.py
index 3d3eeb9230..0dc1c77c53 100644
--- a/django/db/migrations/autodetector.py
+++ b/django/db/migrations/autodetector.py
@@ -12,8 +12,7 @@ from django.db.migrations.questioner import MigrationQuestioner
 from django.db.migrations.utils import (
     COMPILED_REGEX_TYPE, RegexObject, get_migration_name_timestamp,
 )
-
-from .topological_sort import stable_topological_sort
+from django.utils.topological_sort import stable_topological_sort
 
 
 class MigrationAutodetector:
diff --git a/django/db/migrations/topological_sort.py b/django/db/migrations/topological_sort.py
deleted file mode 100644
index e0a22c9236..0000000000
--- a/django/db/migrations/topological_sort.py
+++ /dev/null
@@ -1,32 +0,0 @@
-def topological_sort_as_sets(dependency_graph):
-    """
-    Variation of Kahn's algorithm (1962) that returns sets.
-
-    Take a dependency graph as a dictionary of node => dependencies.
-
-    Yield sets of items in topological order, where the first set contains
-    all nodes without dependencies, and each following set contains all
-    nodes that may depend on the nodes only in the previously yielded sets.
-    """
-    todo = dependency_graph.copy()
-    while todo:
-        current = {node for node, deps in todo.items() if not deps}
-
-        if not current:
-            raise ValueError('Cyclic dependency in graph: {}'.format(
-                ', '.join(repr(x) for x in todo.items())))
-
-        yield current
-
-        # remove current from todo's nodes & dependencies
-        todo = {node: (dependencies - current) for node, dependencies in
-                todo.items() if node not in current}
-
-
-def stable_topological_sort(l, dependency_graph):
-    result = []
-    for layer in topological_sort_as_sets(dependency_graph):
-        for node in l:
-            if node in layer:
-                result.append(node)
-    return result