implemented migrate --fake, closes #15

src/pymongo_migrate/cli.py

@@ -72,8 +72,15 @@ def wrap_with_client(uri, migrations, collection, verbose, *args, **kwargs):
     return wrap_with_client
 
 
+def _decorate(f, *decorators):
+    for decorator in reversed(decorators):
+        f = decorator(f)
+    return f
+
+
 def mongo_migration_options(f):
-    decorators = [
+    return _decorate(
+        f,
         click.option(
             "-u",
             "--uri",
@@ -99,10 +106,7 @@ def mongo_migration_options(f):
         ),
         click.option("-v", "--verbose", count=True),
         mongo_migrate_decor,
-    ]
-    for decorator in reversed(decorators):
-        f = decorator(f)
-    return f
+    )
 
 
 @cli.command(short_help="show migrations and their status")
@@ -123,27 +127,33 @@ def show(mongo_migrate):
         click.echo(f"{migration.name.ljust(name_len_max)}\t" + applied_text)
 
 
+def migrate_cmd_options(f):
+    return _decorate(
+        f,
+        mongo_migration_options,
+        click.argument("migration", required=False),
+        click.option("--fake", is_flag=True),
+    )
+
+
 @cli.command(
     short_help="automagically apply necessary upgrades or downgrades to reach target migration"
 )
-@mongo_migration_options
-@click.argument("migration", required=False)
-def migrate(mongo_migrate, migration=None):
-    mongo_migrate.migrate(migration)
+@migrate_cmd_options
+def migrate(mongo_migrate, migration=None, fake=False):
+    mongo_migrate.migrate(migration, fake=fake)
 
 
 @cli.command(short_help="apply necessary upgrades to reach target migration")
-@mongo_migration_options
-@click.argument("migration", required=False)
-def upgrade(mongo_migrate, migration=None):
-    mongo_migrate.upgrade(migration)
+@migrate_cmd_options
+def upgrade(mongo_migrate, migration=None, fake=False):
+    mongo_migrate.upgrade(migration, fake=fake)
 
 
 @cli.command(short_help="apply necessary downgrades to reach target migration")
-@mongo_migration_options
-@click.argument("migration", required=False)
-def downgrade(mongo_migrate, migration):
-    mongo_migrate.downgrade(migration)
+@migrate_cmd_options
+def downgrade(mongo_migrate, migration, fake=False):
+    mongo_migrate.downgrade(migration, fake=fake)
 
 
 @cli.command()

src/pymongo_migrate/mongo_migrate.py

@@ -116,36 +116,42 @@ def _check_for_migration(
             raise ValueError(f"No such migration: {migration_name}")
         return migration
 
-    def migrate(self, migration_name: Optional[str] = None):
+    def migrate(self, migration_name: Optional[str] = None, fake: bool = False):
         """
         Automatically detects if upgrades or downgrades should be applied to
         reach target migration state.
 
         :param migration_name:
             target migration
             None if all upgrades should be applied
+        :param fake:
+            If True, only migration state in database will be modified and
+            no actual migration will be run.
         """
         if migration_name is None:
             self.logger.debug("Migration target not specified, assuming upgrade")
-            self.upgrade()
+            self.upgrade(fake=fake)
             return
         migration = self._check_for_migration(migration_name)
         assert migration, "No matching migration, something went wrong"
         migration_state = self.get_state(migration)
         if migration_state.applied:
             self.logger.debug("Migration target already applied, assuming downgrade")
-            self.downgrade(migration_name)
+            self.downgrade(migration_name, fake)
         else:
             self.logger.debug("Migration target not applied, assuming upgrade")
-            self.upgrade(migration_name)
+            self.upgrade(migration_name, fake)
 
-    def upgrade(self, migration_name: Optional[str] = None):
+    def upgrade(self, migration_name: Optional[str] = None, fake: bool = False):
         """
         Apply upgrade migrations.
 
         :param migration_name:
             name of migration up to which (including) upgrades should be executed
             None if all migrations should be run
+        :param fake:
+            If True, only migration state in database will be modified and
+            no actual migration will be run.
         """
         self._check_for_migration(migration_name)
         for migration in self.graph:
@@ -155,24 +161,30 @@ def upgrade(self, migration_name: Optional[str] = None):
                     "Migration %r already applied, skipping", migration.name
                 )
                 continue
-            self.logger.info("Running upgrade migration %r", migration.name)
-            with _MeasureTime() as mt:
-                migration.upgrade(self.db)
-                self.logger.info(
-                    "Execution time of %r: %s seconds", migration.name, mt.elapsed
-                )
+            if fake:
+                self.logger.info("Fake running upgrade migration %r", migration.name)
+            else:
+                self.logger.info("Running upgrade migration %r", migration.name)
+                with _MeasureTime() as mt:
+                    migration.upgrade(self.db)
+                    self.logger.info(
+                        "Execution time of %r: %s seconds", migration.name, mt.elapsed
+                    )
             migration_state.applied = dt()
             self.set_state(migration_state)
             if migration.name == migration_name:
                 break
 
-    def downgrade(self, migration_name: Optional[str]):
+    def downgrade(self, migration_name: Optional[str] = None, fake: bool = False):
         """
         Reverse migrations.
 
         :param migration_name:
             name of migration down to which (excluding) downgrades should be executed
             None if all migrations should be run
+        :param fake:
+            If True, only migration state in database will be modified and
+            no actual migration will be run.
         """
         self._check_for_migration(migration_name)
         for migration in reversed(list(self.get_migrations())):
@@ -184,12 +196,15 @@ def downgrade(self, migration_name: Optional[str]):
                     "Migration %r not yet applied, skipping", migration.name
                 )
                 continue
-            self.logger.info("Running downgrade migration %r", migration.name)
-            with _MeasureTime() as mt:
-                migration.downgrade(self.db)
-                self.logger.info(
-                    "Execution time of %r: %s seconds", migration.name, mt.elapsed
-                )
+            if fake:
+                self.logger.info("Fake running downgrade migration %r", migration.name)
+            else:
+                self.logger.info("Running downgrade migration %r", migration.name)
+                with _MeasureTime() as mt:
+                    migration.downgrade(self.db)
+                    self.logger.info(
+                        "Execution time of %r: %s seconds", migration.name, mt.elapsed
+                    )
             migration_state.applied = None
             self.set_state(migration_state)
 

tests/test_cli.py

@@ -73,6 +73,15 @@ def test_migrate(invoker, db, db_uri, migrations_dir):
     assert "Running upgrade migration '20150612230153'" in result.stdout
 
 
+def test_migrate_fake(invoker, db, db_uri, migrations_dir):
+    result = invoker(
+        ["migrate", "-u", db_uri, "-m", migrations_dir, "--fake"],
+        catch_exceptions=False,
+    )
+
+    assert "Fake running upgrade migration '20150612230153'" in result.stdout
+
+
 def test_migrate_verbose(invoker, db, db_uri, migrations_dir):
     result = invoker(
         ["migrate", "-u", db_uri, "-m", migrations_dir, "-vv"], catch_exceptions=False

tests/test_mongo_migrate.py

@@ -26,6 +26,19 @@ def test_upgrade(mongo_migrate, db, get_db_migrations):
     assert db.numbers_collection.count_documents({}) == 499
 
 
+@freezegun.freeze_time("2019-02-03 04:05:06")
+def test_upgrade_fake(mongo_migrate, db, get_db_migrations):
+    mongo_migrate.upgrade(fake=True)
+
+    db_migrations = get_db_migrations()
+    assert db_migrations == [
+        {"applied": dt(2019, 2, 3, 4, 5, 6), "name": "20150612230153"},
+        {"applied": dt(2019, 2, 3, 4, 5, 6), "name": "20181123000000_gt_500"},
+    ]
+
+    assert db.numbers_collection.count_documents({}) == 0
+
+
 @freezegun.freeze_time("2019-02-03 04:05:06")
 def test_upgrade_skip_applied(mongo_migrate, db, db_collection, get_db_migrations):
     db_collection.insert_one(
@@ -56,6 +69,19 @@ def test_downgrade(mongo_migrate, db, get_db_migrations):
     assert db.list_collection_names() == []
 
 
+def test_downgrade_fake(mongo_migrate, db, get_db_migrations):
+    mongo_migrate.upgrade()
+    mongo_migrate.downgrade(fake=True)
+
+    db_migrations = get_db_migrations()
+    assert db_migrations == [
+        {"applied": None, "name": "20150612230153"},
+        {"applied": None, "name": "20181123000000_gt_500"},
+    ]
+
+    assert db.numbers_collection.count_documents({}) == 499
+
+
 def test_upgrade_n_downgrade(mongo_migrate, db, get_db_migrations):
     mongo_migrate.upgrade()
     mongo_migrate.downgrade(None)