Support "check" command (Fixes #502)

docs/index.rst

@@ -151,6 +151,9 @@ After the extension is initialized, a ``db`` group will be added to the command-
 - ``flask db migrate [--message MESSAGE] [--sql] [--head HEAD] [--splice] [--branch-label BRANCH_LABEL] [--version-path VERSION_PATH] [--rev-id REV_ID]``
     Equivalent to ``revision --autogenerate``. The migration script is populated with changes detected automatically. The generated script should to be reviewed and edited as not all types of changes can be detected automatically. This command does not make any changes to the database, just creates the revision script.
 
+- ``flask db check``
+    Checks that a ``migrate`` command would not generate any changes. If pending changes are detected, the command exits with a non-zero status code.
+
 - ``flask db edit <revision>``
     Edit a revision script using $EDITOR.
 

setup.cfg

@@ -27,7 +27,7 @@ python_requires = >=3.6
 install_requires =
     Flask >= 0.9
     Flask-SQLAlchemy >= 1.0
-    alembic >= 0.7
+    alembic >= 1.9.0
 
 [options.packages.find]
 where = src

src/flask_migrate/__init__.py

@@ -257,3 +257,10 @@ def stamp(directory=None, revision='head', sql=False, tag=None):
     migrations"""
     config = current_app.extensions['migrate'].migrate.get_config(directory)
     command.stamp(config, revision, sql=sql, tag=tag)
+
+
+@catch_errors
+def check(directory=None):
+    """Check if there are any new operations to migrate"""
+    config = current_app.extensions['migrate'].migrate.get_config(directory)
+    command.check(config)

src/flask_migrate/cli.py

@@ -14,6 +14,7 @@
 from flask_migrate import branches as _branches
 from flask_migrate import current as _current
 from flask_migrate import stamp as _stamp
+from flask_migrate import check as _check
 
 
 @click.group()
@@ -239,3 +240,12 @@ def stamp(directory, sql, tag, revision):
     """'stamp' the revision table with the given revision; don't run any
     migrations"""
     _stamp(directory, revision, sql, tag)
+
+
+@db.command()
+@click.option('-d', '--directory', default=None,
+              help=('Migration script directory (default is "migrations")'))
+@with_appcontext
+def check(directory):
+    """Check if there are any new operations to migrate"""
+    _check(directory)

tests/test_migrate.py

@@ -56,10 +56,16 @@ def test_alembic_version(self):
     def test_migrate_upgrade(self):
         (o, e, s) = run_cmd('app.py', 'flask db init')
         self.assertTrue(s == 0)
+        (o, e, s) = run_cmd('app.py', 'flask db check')
+        self.assertTrue(s != 0)
         (o, e, s) = run_cmd('app.py', 'flask db migrate')
         self.assertTrue(s == 0)
+        (o, e, s) = run_cmd('app.py', 'flask db check')
+        self.assertTrue(s != 0)
         (o, e, s) = run_cmd('app.py', 'flask db upgrade')
         self.assertTrue(s == 0)
+        (o, e, s) = run_cmd('app.py', 'flask db check')
+        self.assertTrue(s == 0)
 
         from .app import app, db, User
         with app.app_context():