TypeError: unbound method _compiler_dispatch() must be called with Text instance as first argument

[Martijn van Oosterhout]

There appears to be a problem using with_variant with sqlite. Consider this example program:

import sqlalchemy
from sqlalchemy import Text, Column, create_engine
from sqlalchemy.ext.declarative import declarative_base

#MyType = Text().with_variant(Text, 'postgresql')   # works
MyType = Text().with_variant(Text, 'sqlite')    # breaks

Base = declarative_base()

Base.metadata.bind = create_engine('sqlite://')

class TestTable(Base):
    __tablename__ = 'test'
    column = Column('test', MyType, primary_key=True)

print sqlalchemy.__version__
Base.metadata.create_all()

Dies for me with the following error on 0.8.4 and 0.9.6:

Traceback (most recent call last):
  File "test2.py", line 17, in <module>
    Base.metadata.create_all()
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/schema.py", line 2848, in create_all
    tables=tables)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1479, in _run_visitor
    conn._run_visitor(visitorcallable, element, **kwargs)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1122, in _run_visitor
    **kwargs).traverse_single(element)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 122, in traverse_single
    return meth(obj, **kw)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/ddl.py", line 70, in visit_metadata
    self.traverse_single(table, create_ok=True)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 122, in traverse_single
    return meth(obj, **kw)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/ddl.py", line 89, in visit_table
    self.connection.execute(schema.CreateTable(table))
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 662, in execute
    params)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 714, in _execute_ddl
    compiled = ddl.compile(dialect=dialect)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/expression.py", line 1920, in compile
    return self._compiler(dialect, bind=bind, **kw)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/schema.py", line 2954, in _compiler
    return dialect.ddl_compiler(dialect, self, **kw)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/interfaces.py", line 804, in __init__
    self.string = self.process(self.statement, **compile_kwargs)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/interfaces.py", line 823, in process
    return obj._compiler_dispatch(self, **kwargs)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 80, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 1941, in visit_create_table
    and not first_pk)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/interfaces.py", line 823, in process
    return obj._compiler_dispatch(self, **kwargs)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 80, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 1980, in visit_create_column
    first_pk=first_pk
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/dialects/sqlite/base.py", line 484, in get_column_specification
    coltype = self.dialect.type_compiler.process(column.type)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/interfaces.py", line 869, in process
    return type_._compiler_dispatch(self)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 80, in _compiler_dispatch
    return meth(self, **kw)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 2366, in visit_type_decorator
    return self.process(type_.type_engine(self.dialect))
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/interfaces.py", line 869, in process
    return type_._compiler_dispatch(self)
TypeError: unbound method _compiler_dispatch() must be called with Text instance as first argument (got SQLiteTypeCompiler instance instead)

If you use the line involving 'postgresql' instead, it works just fine.

[Mike Bayer]

• The :meth:.TypeEngine.with_variant method will now accept a type class as an argument which is internally converted to an instance, using the same convention long established by other constructs such as :class:.Column. fixes #3122

→ <<cset e5d0fa94937b>>

[Mike Bayer]

• The :meth:.TypeEngine.with_variant method will now accept a type class as an argument which is internally converted to an instance, using the same convention long established by other constructs such as :class:.Column. fixes #3122

→ <<cset 6ef47a46c1cd>>

[Mike Bayer]

use Text() for now.

[Martijn van Oosterhout]

Hmm, I thought I tested that but that works.

Why it happened to work for PostgreSQL who knows. But that might explain why this went unnoticed for so long: SQLite only supports basic types, so the variant would almost always have been for another database.

I see in the test you use 'postgresql', I hope that doesn't mask anything.

Thanks for the quick fix.

(sorry if you get this twice, the interface is confusing me)

[Mike Bayer]

if you take the patch out and run the test, it fails with the above stack trace. that's how we know the test covers the issue. (also I know what the issue is).