sqlalchemy 2.0.51: orm.decl_api.DeclarativeMeta

# sqlalchemy DeclarativeMeta API

This sample pins `sqlalchemy` 2.0.51 and verifies `sqlalchemy.orm.decl_api.DeclarativeMeta` for declarative class mapping and metaclass customization.

The contract verifies:
- Base classes produced by declarative_base() have DeclarativeMeta as their metaclass, and models subclassing the base are instances of DeclarativeMeta.
- Custom declarative base classes can be defined directly using metaclass=DeclarativeMeta when configured with registry and __abstract__ = True.
- Defining a class directly with metaclass=DeclarativeMeta without providing a registry raises InvalidRequestError.
- Classes instantiated through DeclarativeMeta initialize table metadata and map columns to their underlying Table representation.
- Custom metaclasses subclassing DeclarativeMeta can hook into model initialization while remaining DeclarativeMeta instances.

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify sqlalchemy.orm.decl_api.DeclarativeMeta in pkg:pypi/sqlalchemy@2.0.51
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:pypi/sqlalchemy@2.0.51
Demonstrate these symbols/APIs:
  - sqlalchemy.orm.decl_api.DeclarativeMeta

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:3d4494d60557564e170000656eb13fab1bf2d88a3abdf5fbd13c327b4e8f13cf","contract":["Base classes produced by declarative_base() have DeclarativeMeta as their metaclass, and models subclassing the base are instances of DeclarativeMeta.","Custom declarative base classes can be defined directly using metaclass=DeclarativeMeta when configured with registry and __abstract__ = True.","Defining a class directly with metaclass=DeclarativeMeta without providing a registry raises InvalidRequestError.","Classes instantiated through DeclarativeMeta initialize table metadata and map columns to their underlying Table representation.","Custom metaclasses subclassing DeclarativeMeta can hook into model initialization while remaining DeclarativeMeta instances."],"goal":"verify sqlalchemy.orm.decl_api.DeclarativeMeta in pkg:pypi/sqlalchemy@2.0.51","kind":"HOW","packages":["pkg:pypi/sqlalchemy@2.0.51"],"schemaVersion":1,"symbols":["sqlalchemy.orm.decl_api.DeclarativeMeta"]},"contractCommand":["python","test/contract.py"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"pypi","executionContext":"python","language":"python","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"pip","runtime":"python","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/sqlalchemy@2.0.51"],"schemaVersion":1,"subject":"pkg:pypi/sqlalchemy@2.0.51","symbols":["sqlalchemy.orm.decl_api.DeclarativeMeta"],"verifierAdapter":"python@1"}

sqlalchemy==2.0.51

{
  "schemaVersion": 1,
  "goal": "verify sqlalchemy.orm.decl_api.DeclarativeMeta in pkg:pypi/sqlalchemy@2.0.51",
  "kind": "HOW",
  "packages": [
    "pkg:pypi/sqlalchemy@2.0.51"
  ],
  "symbols": [
    "sqlalchemy.orm.decl_api.DeclarativeMeta"
  ]
}

import sqlalchemy
from sqlalchemy.orm.decl_api import DeclarativeMeta
from sqlalchemy.orm import declarative_base, registry
from sqlalchemy import Column, Integer, String
from sqlalchemy.exc import InvalidRequestError

# 1. Base created by declarative_base() has DeclarativeMeta metaclass, as do its subclasses
Base = declarative_base()
assert isinstance(Base, DeclarativeMeta)
assert type(Base) is DeclarativeMeta

class User(Base):
    __tablename__ = "users"
    id = Column(Integer, primary_key=True)
    name = Column(String(50))

assert isinstance(User, DeclarativeMeta)
assert type(User) is DeclarativeMeta
assert hasattr(User, "__table__")
assert User.__table__.name == "users"

# 2. Custom declarative base using metaclass=DeclarativeMeta directly with registry and __abstract__
reg = registry()
class CustomBase(metaclass=DeclarativeMeta):
    __abstract__ = True
    registry = reg
    metadata = reg.metadata

class Item(CustomBase):
    __tablename__ = "items"
    id = Column(Integer, primary_key=True)
    description = Column(String(100))

assert isinstance(Item, DeclarativeMeta)
assert Item.__table__.name == "items"
assert Item in reg.mappers or reg._class_registry.get("Item") is Item
assert "items" in reg.metadata.tables

# 3. Defining a class directly with metaclass=DeclarativeMeta without registry raises InvalidRequestError
try:
    class InvalidClass(metaclass=DeclarativeMeta):
        pass
    assert False, "Expected InvalidRequestError when creating DeclarativeMeta class without registry"
except InvalidRequestError as exc:
    assert "Declarative base class has no 'registry' attribute" in str(exc)

# 4. Classes instantiated through DeclarativeMeta initialize table metadata and map columns
assert "id" in User.__table__.c
assert "name" in User.__table__.c
assert User.__table__.primary_key.columns.contains_column(User.__table__.c.id)

# 5. Custom metaclass subclassing DeclarativeMeta can hook into model initialization
class CustomMeta(DeclarativeMeta):
    def __init__(cls, classname, bases, dict_):
        super().__init__(classname, bases, dict_)
        cls._meta_custom_initialized = True

CustomBaseWithMeta = declarative_base(metaclass=CustomMeta)
class Product(CustomBaseWithMeta):
    __tablename__ = "products"
    id = Column(Integer, primary_key=True)

assert isinstance(Product, DeclarativeMeta)
assert isinstance(Product, CustomMeta)
assert getattr(Product, "_meta_custom_initialized", False) is True

print("CONTRACT PASS: sqlalchemy.orm.decl_api.DeclarativeMeta verified offline")