How to use the emmett.orm.Field function in emmett

def test_step_four_alter_table(app):
    db = Database(app, auto_migrate=False)
    db.define_models(StepFourThing)
    ops = _make_ops(db)
    db2 = Database(app, auto_migrate=False)
    db2.define_models(StepFourThingEdit)
    ops2 = _make_ops(db2, ops)
    sql = []
    for op in ops2.ops:
        sql.append(_make_sql(db2, op))
    assert "\n".join(sql) == _step_four_sql


class StepFiveThing(Model):
    name = Field()
    value = Field.int()
    created_at = Field.datetime()

    indexes = {
        'name': True,
        ('name', 'value'): True
    }


class StepFiveThingEdit(StepFiveThing):
    tablename = "step_five_things"

    indexes = {
        'name': False,
        'name_created': {
            'fields': 'name',
            'expressions': lambda m: m.created_at.coalesce(None)}

ops2 = _make_ops(db2, ops)
    op = ops2.ops[0]
    sql = _make_sql(db, op)
    assert sql == _step_three_sql_drop


class StepFourThing(Model):
    name = Field(notnull=True)
    value = Field.float(default=8.8)
    available = Field.bool(default=True)
    asd = Field()


class StepFourThingEdit(Model):
    tablename = "step_four_things"
    name = Field()
    value = Field.float()
    available = Field.bool(default=True)
    asd = Field.int()

_step_four_sql = """ALTER TABLE "step_four_things" ALTER COLUMN "name" DROP NOT NULL;
ALTER TABLE "step_four_things" ALTER COLUMN "value" DROP DEFAULT;
ALTER TABLE "step_four_things" ALTER COLUMN "asd" TYPE INTEGER;"""


def test_step_four_alter_table(app):
    db = Database(app, auto_migrate=False)
    db.define_models(StepFourThing)
    ops = _make_ops(db)
    db2 = Database(app, auto_migrate=False)
    db2.define_models(StepFourThingEdit)
    ops2 = _make_ops(db2, ops)

db = Database(app, auto_migrate=False)
    db.define_models(StepThreeThingTwo)
    ops = _make_ops(db)
    db2 = Database(app, auto_migrate=False)
    db2.define_models(StepThreeThingThree)
    ops2 = _make_ops(db2, ops)
    op = ops2.ops[0]
    sql = _make_sql(db, op)
    assert sql == _step_three_sql_drop


class StepFourThing(Model):
    name = Field(notnull=True)
    value = Field.float(default=8.8)
    available = Field.bool(default=True)
    asd = Field()


class StepFourThingEdit(Model):
    tablename = "step_four_things"
    name = Field()
    value = Field.float()
    available = Field.bool(default=True)
    asd = Field.int()

_step_four_sql = """ALTER TABLE "step_four_things" ALTER COLUMN "name" DROP NOT NULL;
ALTER TABLE "step_four_things" ALTER COLUMN "value" DROP DEFAULT;
ALTER TABLE "step_four_things" ALTER COLUMN "asd" TYPE INTEGER;"""


def test_step_four_alter_table(app):
    db = Database(app, auto_migrate=False)

assert sql == _step_two_sql


class StepThreeThingOne(Model):
    a = Field()


class StepThreeThingTwo(Model):
    tablename = "step_three_thing_ones"
    a = Field()
    b = Field()


class StepThreeThingThree(Model):
    tablename = "step_three_thing_ones"
    b = Field()

_step_three_sql = 'ALTER TABLE "step_three_thing_ones" ADD "b" CHAR(512);'
_step_three_sql_drop = 'ALTER TABLE "step_three_thing_ones" DROP COLUMN "a";'


def test_step_three_create_column(app):
    db = Database(app, auto_migrate=False)
    db.define_models(StepThreeThingOne)
    ops = _make_ops(db)
    db2 = Database(app, auto_migrate=False)
    db2.define_models(StepThreeThingTwo)
    ops2 = _make_ops(db2, ops)
    op = ops2.ops[0]
    sql = _make_sql(db, op)
    assert sql == _step_three_sql

----------------------

    Test pyDAL transactions implementation over Emmett.

    :copyright: (c) 2014-2019 by Giovanni Barillari
    :license: BSD, see LICENSE for more details.
"""

import pytest

from emmett import App, sdict
from emmett.orm import Database, Field, Model


class Register(Model):
    value = Field.int()


@pytest.fixture(scope='module')
def db():
    app = App(__name__)
    db = Database(
        app, config=sdict(
            uri='sqlite:memory', auto_migrate=True, auto_connect=True))
    db.define_models(Register)
    return db


@pytest.fixture(scope='function')
def cleanup(request, db):
    def teardown():
        Register.all().delete()

def test_step_two_create_table(app):
    db = Database(app, auto_migrate=False)
    db.define_models(StepTwoThing)
    ops = _make_ops(db)
    op = ops.ops[0]
    sql = _make_sql(db, op)
    assert sql == _step_two_sql


class StepThreeThingOne(Model):
    a = Field()


class StepThreeThingTwo(Model):
    tablename = "step_three_thing_ones"
    a = Field()
    b = Field()


class StepThreeThingThree(Model):
    tablename = "step_three_thing_ones"
    b = Field()

_step_three_sql = 'ALTER TABLE "step_three_thing_ones" ADD "b" CHAR(512);'
_step_three_sql_drop = 'ALTER TABLE "step_three_thing_ones" DROP COLUMN "a";'


def test_step_three_create_column(app):
    db = Database(app, auto_migrate=False)
    db.define_models(StepThreeThingOne)
    ops = _make_ops(db)
    db2 = Database(app, auto_migrate=False)

def login_fields(auth):
    model = auth.models['user']
    rv = {
        'email': Field(
            validation={'is': 'email', 'presence': True},
            label=model.email.label),
        'password': Field(
            'password', validation=model.password._requires,
            label=model.password.label)
    }
    if auth.ext.config.remember_option:
        rv['remember'] = Field(
            'bool', default=True,
            label=auth.ext.config.messages['remember_button'])
    return rv

def login_fields(auth):
    model = auth.models['user']
    rv = {
        'email': Field(
            validation={'is': 'email', 'presence': True},
            label=model.email.label),
        'password': Field(
            'password', validation=model.password._requires,
            label=model.password.label)
    }
    if auth.ext.config.remember_option:
        rv['remember'] = Field(
            'bool', default=True,
            label=auth.ext.config.messages['remember_button'])
    return rv

def password_change_fields(auth):
    password_validation = auth.ext.config.models['user'].password._requires
    rv = {
        'old_password': Field(
            'password', validation=password_validation,
            label=auth.ext.config.messages['old_password']),
        'new_password': Field(
            'password', validation=password_validation,
            label=auth.ext.config.messages['new_password']),
        'new_password2': Field(
            'password', label=auth.ext.config.messages['verify_password'])
    }
    return rv