Fixed #31318 -- Allowed sqlmigrate to inspect squashed migrations.

3 files changed, 37 insertions, 21 deletions

diff --git a/django/core/management/commands/sqlmigrate.py b/django/core/management/commands/sqlmigrate.py
index 2acb789c00..aee793fc14 100644
--- a/django/core/management/commands/sqlmigrate.py
+++ b/django/core/management/commands/sqlmigrate.py
@@ -32,8 +32,9 @@ class Command(BaseCommand):
         # Get the database we're operating from
         connection = connections[options['database']]
 
-        # Load up an loader to get all the migration data
-        loader = MigrationLoader(connection)
+        # Load up an loader to get all the migration data, but don't replace
+        # migrations.
+        loader = MigrationLoader(connection, replace_migrations=False)
 
         # Resolve command-line arguments into a migration
         app_label, migration_name = options['app_label'], options['migration_name']
diff --git a/django/db/migrations/loader.py b/django/db/migrations/loader.py
index d41f6d3606..80945d0ffd 100644
--- a/django/db/migrations/loader.py
+++ b/django/db/migrations/loader.py
@@ -40,11 +40,15 @@ class MigrationLoader:
     in memory.
     """
 
-    def __init__(self, connection, load=True, ignore_no_migrations=False):
+    def __init__(
+        self, connection, load=True, ignore_no_migrations=False,
+        replace_migrations=True,
+    ):
         self.connection = connection
         self.disk_migrations = None
         self.applied_migrations = None
         self.ignore_no_migrations = ignore_no_migrations
+        self.replace_migrations = replace_migrations
         if load:
             self.build_graph()
 
@@ -223,24 +227,27 @@ class MigrationLoader:
         # Add external dependencies now that the internal ones have been resolved.
         for key, migration in self.disk_migrations.items():
             self.add_external_dependencies(key, migration)
-        # Carry out replacements where possible.
-        for key, migration in self.replacements.items():
-            # Get applied status of each of this migration's replacement targets.
-            applied_statuses = [(target in self.applied_migrations) for target in migration.replaces]
-            # Ensure the replacing migration is only marked as applied if all of
-            # its replacement targets are.
-            if all(applied_statuses):
-                self.applied_migrations[key] = migration
-            else:
-                self.applied_migrations.pop(key, None)
-            # A replacing migration can be used if either all or none of its
-            # replacement targets have been applied.
-            if all(applied_statuses) or (not any(applied_statuses)):
-                self.graph.remove_replaced_nodes(key, migration.replaces)
-            else:
-                # This replacing migration cannot be used because it is partially applied.
-                # Remove it from the graph and remap dependencies to it (#25945).
-                self.graph.remove_replacement_node(key, migration.replaces)
+        # Carry out replacements where possible and if enabled.
+        if self.replace_migrations:
+            for key, migration in self.replacements.items():
+                # Get applied status of each of this migration's replacement
+                # targets.
+                applied_statuses = [(target in self.applied_migrations) for target in migration.replaces]
+                # The replacing migration is only marked as applied if all of
+                # its replacement targets are.
+                if all(applied_statuses):
+                    self.applied_migrations[key] = migration
+                else:
+                    self.applied_migrations.pop(key, None)
+                # A replacing migration can be used if either all or none of
+                # its replacement targets have been applied.
+                if all(applied_statuses) or (not any(applied_statuses)):
+                    self.graph.remove_replaced_nodes(key, migration.replaces)
+                else:
+                    # This replacing migration cannot be used because it is
+                    # partially applied. Remove it from the graph and remap
+                    # dependencies to it (#25945).
+                    self.graph.remove_replacement_node(key, migration.replaces)
         # Ensure the graph is consistent.
         try:
             self.graph.validate_consistency()
diff --git a/tests/migrations/test_commands.py b/tests/migrations/test_commands.py
index 7fd1a68422..14c09c8f98 100644
--- a/tests/migrations/test_commands.py
+++ b/tests/migrations/test_commands.py
@@ -713,6 +713,14 @@ class MigrateTests(MigrationTestBase):
         self.assertIn('-- create model book', output)
         self.assertNotIn('-- create model tribble', output)
 
+    @override_settings(MIGRATION_MODULES={'migrations': 'migrations.test_migrations_squashed'})
+    def test_sqlmigrate_replaced_migration(self):
+        out = io.StringIO()
+        call_command('sqlmigrate', 'migrations', '0001_initial', stdout=out)
+        output = out.getvalue().lower()
+        self.assertIn('-- create model author', output)
+        self.assertIn('-- create model tribble', output)
+
     @override_settings(MIGRATION_MODULES={'migrations': 'migrations.test_migrations_no_operations'})
     def test_migrations_no_operations(self):
         err = io.StringIO()