Cannot register custom range type using register_range

[Takuya Miyamoto]

Please complete the following information:

• OS: Linux
• Psycopg version: 2.9.5
• Python version: 3.11
• PostgreSQL version: 11.22
• pip version: 23.3.1

Describe the bug

Please let us know:

1: what you did

I registered my custom range type using register_range with flask-sqlalchemy

2: what you expected to happen

I expected my custom range type will be registered correctly.

3: what happened instead

I got the following error.

  File "/usr/local/app/app.py", line 22, in <module>
    TimeRange.register(engine)
  File "/usr/local/app/app.py", line 11, in register
    register_range('timerange', cls, conn, globally=True)
  File "/home/user/.cache/pypoetry/virtualenvs/wifishare-pyapi-woE4c0CP-py3.11/lib/python3.11/site-packages/psycopg2/_range.py", line 232, in register_range
    caster = RangeCaster._from_db(pgrange, pyrange, conn_or_curs)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/user/.cache/pypoetry/virtualenvs/wifishare-pyapi-woE4c0CP-py3.11/lib/python3.11/site-packages/psycopg2/_range.py", line 351, in _from_db
    if conn.info.server_version < 90200:
       ^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'dict' object has no attribute 'server_version'

If possible, provide a script reproducing the issue.

from psycopg2.extras import Range
from psycopg2.extras import register_range


class TimeRange(Range):
  @classmethod
  def register(cls, engine):
      conn = engine.raw_connection()
      register_range('timerange', cls, conn, globally=True)
      conn.close()


db = SQLAlchemy(session_options={})

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://username:password@localhost:port/DBNAME'

db.init_app(app)
engine = db.get_engine(app)
TimeRange.register(engine)

flask: 2.0.0
flask-sqlalchemy: 2.5.0
sqlalchemy: 1.4.52

[Daniele Varrazzo]

If conn.info is a dict then conn is not a psycopg2 connection. I don't know what engine.raw_connection() returns, it's something in SQLAlchemy.