Alembic --autogenerate fails for me

Question

The command I'm running:

 alembic -c development.ini revision --autogenerate -m "test"

I get the following result:

Traceback (most recent call last):
  File "/Users/charleswesley/.virtualenvs/foundation/bin/alembic", line 9, in <module>
    load_entry_point('alembic==0.6.1', 'console_scripts', 'alembic')()
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/config.py", line 298, in main
    CommandLine(prog=prog).main(argv=argv)
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/config.py", line 293, in main
    self.run_cmd(cfg, options)
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/config.py", line 279, in run_cmd
    **dict((k, getattr(options, k)) for k in kwarg)
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/command.py", line 97, in revision
    script.run_env()
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/script.py", line 199, in run_env
    util.load_python_file(self.dir, 'env.py')
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/util.py", line 198, in load_python_file
    module = load_module(module_id, path)
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/compat.py", line 49, in load_module
    return machinery.SourceFileLoader(module_id, path).load_module()
  File "<frozen importlib._bootstrap>", line 586, in _check_name_wrapper
  File "<frozen importlib._bootstrap>", line 1024, in load_module
  File "<frozen importlib._bootstrap>", line 1005, in load_module
  File "<frozen importlib._bootstrap>", line 562, in module_for_loader_wrapper
  File "<frozen importlib._bootstrap>", line 870, in _load_module
  File "<frozen importlib._bootstrap>", line 313, in _call_with_frames_removed
  File "/Users/charleswesley/repos/foundation/foundation/scripts/alembic/env.py", line 74, in <module>
    run_migrations_online()
  File "/Users/charleswesley/repos/foundation/foundation/scripts/alembic/env.py", line 67, in run_migrations_online
    context.run_migrations()
  File "<string>", line 7, in run_migrations
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/environment.py", line 652, in run_migrations
    self.get_context().run_migrations(**kw)
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/migration.py", line 210, in run_migrations
    self):
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/command.py", line 83, in retrieve_migrations
    autogen._produce_migration_diffs(context, template_args, imports)
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/autogenerate/api.py", line 143, in _produce_migration_diffs
    autogen_context, object_filters, include_schemas)
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/autogenerate/api.py", line 198, in _produce_net_changes
    inspector, metadata, diffs, autogen_context)
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/autogenerate/compare.py", line 32, in _compare_tables
    set())
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/autogenerate/compare.py", line 243, in _compare_indexes
    for i in reflected_indexes
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/autogenerate/compare.py", line 243, in <genexpr>
    for i in reflected_indexes
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/autogenerate/compare.py", line 83, in _make_index
    unique=params['unique']
  File "/Users/charleswesley/.virtualenvs/foundation/lib/python3.3/site-packages/alembic-0.6.1-py3.3.egg/alembic/autogenerate/compare.py", line 82, in <listcomp>
    *[conn_table.c[cname] for cname in params['column_names']],
AttributeError: 'NoneType' object has no attribute 'c'

I'm really not sure what might be going wrong here. I'm trying with Postgres 9.2, SQLAlchemy 0.8.4, and Alembic 0.6.1. But I've seen the same result with Postgres 9.3, SQLAlchemy 0.9, and Alembic 0.6.2. We are using custom database schemas, if that makes a difference.

Answer 1

This bug occured to me as well when using custom schemas and alembic. This commit fixes it.