Legacy declaration generator

legacydecl.py

#!/usr/bin/env python
from twisted.python.reflect import namedAny

template = """
declareLegacyItem(
    typeName=%r,
    schemaVersion=%d,
    attributes=dict(
        %s))
"""

_attributeDefaults = [
    ('allowNone', True),
    ('default', None),
    ('defaultFactory', None)]
_attributeDefaultsDict = dict(_attributeDefaults)


def getAttributeAttributes(attr):
    attrs = ((name, getattr(attr, name))
             for name, default
             in _attributeDefaults)
    for name, value in attrs:
        if value != _attributeDefaultsDict[name]:
            if name == 'defaultFactory':
                #raise ValueError('defaultFactory is hard: %r' % (attr,))
                continue
            yield name, value


def emitAttribute((attrName, attr)):
    attrs = ['%s=%r' % (key, value)
             for key, value
             in getAttributeAttributes(attr)]

    return '%s=%s(%s)' % (
        attrName,
        attr.__class__.__name__,
        ', '.join(attrs))


def legacyItemCode(itemClass):
    calculatedAttributes = ',\n        '.join(
        map(emitAttribute, itemClass.getSchema()))
    fmt = template % (itemClass.typeName, itemClass.schemaVersion,
                      calculatedAttributes)
    return fmt


if __name__ == '__main__':
    import sys
    f = sys.stdout
    f.write(legacyItemCode(namedAny(sys.argv[1])))