Demonstrates a bug in Flask-Sqlalchemy where form rules breaks on relationships that do not already have at least one member.

README

Requirements: Postgresql, Flask-Admin, Flask-Sqlalchemy

How to run it:

createdb inline_bug
psql inline_bug -af schema.sql
python app.py

Go to /admin and try to edit the servers.  One will work, one will not.

app.py

from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy
from flask.ext.admin import Admin
from flask.ext.admin.contrib.sqla import ModelView

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgres://localhost:5432/inline_bug'

# Sqlalchemy Reflect
db = SQLAlchemy(app)
connection = db.engine.connect()
db.metadata.reflect(bind=db.engine)

# Models
class Haver(db.Model):
	__table__ = db.metadata.tables['havers']

class Belonger(db.Model):
	__table__ = db.metadata.tables['belongers']
	haver = db.relationship(Haver, backref="belongers")

# Admin Views
class HaverView(ModelView):
	inline_models = (Belonger,)
	form_create_rules = [
		'name',
		'belongers'
	]
	form_edit_rules = form_create_rules

# Create Admin
admin = Admin(app, name="InlineBug")
admin.add_view(HaverView(Haver, db.session))

if __name__ == '__main__':
	app.debug = True
	app.run()

schema.sql

CREATE TABLE havers (
    id serial primary key,
    name varchar(255)
);

CREATE TABLE belongers (
    id serial primary key,
    haver_id serial not null references havers (id) on delete cascade,
    name varchar(255)
);

insert into havers (name) values ('Works'),('Breaks');
insert into belongers (name, haver_id) select 'Belonger', id as haver_id from havers where name = 'Works';