Why are association tables generated as Table and not as Declarative Model?

[dirkdevries96]

I'm interested in generating association table using Declarative Base. This way this table can be referenced elsewhere in a declarative way.

But the readme states the following:

Model class generators

The code generators that generate classes try to generate model classes whenever possible. There are two circumstances in which a Table is generated instead:

• the table has no primary key constraint (which is required by SQLAlchemy for every model class)
• the table is an association table between two other tables (see below for the specifics)

Is there a specific reason why it's done this way? Is perhaps my use case of referencing an association table not good practice?

Below is an expample of the current code generated.

class ProfileType(Base):
    __tablename__ = 'profile_type'

    id = Column(Integer, primary_key=True, server_default=text("nextval('profile_type_id_seq'::regclass)"))
    name = Column(String, unique=True)

    project = relationship('Project', secondary='project_profile_type', back_populates='profile_type')

class Project(Base):
    __tablename__ = 'project'

    id = Column(Integer, primary_key=True, server_default=text("nextval('project_id_seq'::regclass)"))
    name = Column(String)

    profile_type = relationship('ProfileType', secondary='project_profile_type', back_populates='project')


t_project_profile_type = Table(
    'project_profile_type', metadata,
    Column('project_id', ForeignKey('project.id'), primary_key=True, nullable=False),
    Column('profile_type_id', ForeignKey('profile_type.id'), primary_key=True, nullable=False),
    Index('project_profile_type_project_id_profile_type_id_idx', 'project_id', 'profile_type_id', unique=True)
)

[agronholm]

The reason is that SQLAlchemy cannot keep such "association objects", in sync with the relationship attributes, causing some very puzzling bugs. If your intent is to not have a direct many-to-many relationship between Project and ProfileType, that's fine then, but sqlacodegen does not have a way for the user to communicate such intent at the moment, so you'll have to edit the generated code a bit.