Autogenerating creates an empty migration file continually

[ehdgua01]

Is it is a bug or an intended thing?

I defined the Service model that inherits Base and TimestampMixin that has MySQL DATETIME types

from sqlalchemy.dialects import mysql

@as_declarative()
class Base:
    __table_args__: tuple = (
        {
            "mysql_engine": "InnoDB",
            "mysql_charset": "utf8mb4",
        },
    )

    id = sa.Column(sa.BigInteger, autoincrement=True, primary_key=True)


@declarative_mixin
class TimestampMixin:
    created_at = sa.Column(mysql.DATETIME(fsp=6), default=get_aware_now_datetime)
    updated_at = sa.Column(mysql.DATETIME(fsp=6), default=get_aware_now_datetime, onupdate=get_aware_now_datetime)


class Service(TimestampMixin, Base):
    __tablename__ = "service"

    name = sa.Column(sa.String(length=64), unique=True)

And, I ran below commands

poetry run alembic revision --autogenerate -m first
poetry run alembic upgrade head
poetry run alembic revision --autogenerate -m second

Finally, two migrations were created, but the second migration was empty.

79fce76005dc_first.py

"""20211025_160438

Revision ID: 79fce76005dc
Revises: 
Create Date: 2021-10-25 16:04:39.440165

"""
from alembic import op
import sqlalchemy as sa
from sqlalchemy.dialects import mysql

# revision identifiers, used by Alembic.
revision = '79fce76005dc'
down_revision = None
branch_labels = None
depends_on = None


def upgrade():
    # ### commands auto generated by Alembic - please adjust! ###
    op.create_table('service',
    sa.Column('id', sa.BigInteger(), autoincrement=True, nullable=False),
    sa.Column('created_at', mysql.DATETIME(fsp=6), nullable=True),
    sa.Column('updated_at', mysql.DATETIME(fsp=6), nullable=True),
    sa.Column('name', sa.String(length=64), nullable=True),
    sa.PrimaryKeyConstraint('id'),
    sa.UniqueConstraint('name'),
    mysql_charset='utf8mb4',
    mysql_engine='InnoDB'
    )
    # ### end Alembic commands ###


def downgrade():
    # ### commands auto generated by Alembic - please adjust! ###
    op.drop_table('service')
    # ### end Alembic commands ###

9fc474e7b3fc_second.py

"""20211025_160447

Revision ID: 9fc474e7b3fc
Revises: 79fce76005dc
Create Date: 2021-10-25 16:04:48.255282

"""
from alembic import op
import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision = '9fc474e7b3fc'
down_revision = '79fce76005dc'
branch_labels = None
depends_on = None


def upgrade():
    # ### commands auto generated by Alembic - please adjust! ###
    pass
    # ### end Alembic commands ###


def downgrade():
    # ### commands auto generated by Alembic - please adjust! ###
    pass
    # ### end Alembic commands ###

Unfortunately, empty migration was created continually when executing the above commands

[CaselIT]

Hi,

If autogenerate does not detect any change an empty migration is created.
This is to be expected, the command is alembic revision that will by default create an empty revision to be filled by the user.

[ehdgua01]

Hi, ty :)