[wtforms] Using wtforms-json which supports None

UPDATING.md

@@ -27,6 +27,11 @@ assists people when migrating to a new version.
   run `pip install superset[presto]` and/or `pip install superset[hive]` as
   required.
 
+* [5445](https://github.com/apache/incubator-superset/pull/5445) : a change 
+which prevents encoding of empty string from form data in the datanbase. 
+This involves a non-schema changing migration which does potentially impact
+a large number of records. Scheduled downtime may be advised.
+
 ## Superset 0.31.0
 * boto3 / botocore was removed from the dependency list. If you use s3
 as a place to store your SQL Lab result set or Hive uploads, you may

requirements.txt

@@ -42,8 +42,8 @@ kombu==4.2.1              # via celery
 mako==1.0.7               # via alembic
 markdown==3.0
 markupsafe==1.0           # via jinja2, mako
-numpy==1.15.2             # via numpy
-pandas==0.23.4            # via pandas
+numpy==1.15.2             # via pandas
+pandas==0.23.4
 parsedatetime==2.0.0
 pathlib2==2.3.0
 polyline==1.3.2
@@ -60,7 +60,7 @@ requests==2.20.0
 retry==0.9.2
 selenium==3.141.0
 simplejson==3.15.0
-six==1.11.0               # via bleach, cryptography, isodate, pathlib2, polyline, pydruid, python-dateutil, sqlalchemy-utils
+six==1.11.0               # via bleach, cryptography, isodate, pathlib2, polyline, pydruid, python-dateutil, sqlalchemy-utils, wtforms-json
 sqlalchemy-utils==0.32.21
 sqlalchemy==1.2.2
 sqlparse==0.2.4
@@ -69,4 +69,5 @@ urllib3==1.22             # via requests, selenium
 vine==1.1.4               # via amqp
 webencodings==0.5.1       # via bleach
 werkzeug==0.14.1          # via flask
-wtforms==2.2.1            # via flask-wtf
+wtforms-json==0.3.3
+wtforms==2.2.1            # via flask-wtf, wtforms-json

setup.py

@@ -104,6 +104,7 @@ def get_git_sha():
         'sqlalchemy-utils',
         'sqlparse',
         'unicodecsv',
+        'wtforms-json',
     ],
     extras_require={
         'cors': ['flask-cors>=2.0.0'],

superset/__init__.py

@@ -28,13 +28,16 @@
 from flask_migrate import Migrate
 from flask_wtf.csrf import CSRFProtect
 from werkzeug.contrib.fixers import ProxyFix
+import wtforms_json
 
 from superset import config
 from superset.connectors.connector_registry import ConnectorRegistry
 from superset.security import SupersetSecurityManager
 from superset.utils.core import (
     get_update_perms_flag, pessimistic_connection_handling, setup_cache)
 
+wtforms_json.init()
+
 APP_DIR = os.path.dirname(__file__)
 CONFIG_MODULE = os.environ.get('SUPERSET_CONFIG', 'superset.config')
 

superset/migrations/versions/c617da68de7d_form_nullable.py

@@ -0,0 +1,191 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""form nullable
+
+Revision ID: c617da68de7d
+Revises: 18dc26817ad2
+Create Date: 2018-07-19 23:41:32.631556
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = 'c617da68de7d'
+down_revision = '18dc26817ad2'
+
+from alembic import op
+from sqlalchemy.ext.declarative import declarative_base
+from sqlalchemy import Column, Integer, String, Text
+
+from superset import db
+from superset.utils.core import MediumText
+
+Base = declarative_base()
+
+
+class BaseColumnMixin(object):
+    id = Column(Integer, primary_key=True)
+    column_name = Column(String(255))
+    description = Column(Text)
+    type = Column(String(32))
+    verbose_name = Column(String(1024))
+
+
+class BaseDatasourceMixin(object):
+    id = Column(Integer, primary_key=True)
+    description = Column(Text)
+
+
+class BaseMetricMixin(object):
+    id = Column(Integer, primary_key=True)
+    d3format = Column(String(128))
+    description = Column(Text)
+    metric_name = Column(String(512))
+    metric_type = Column(String(32))
+    verbose_name = Column(String(1024))
+    warning_text = Column(Text)
+
+
+class Annotation(Base):
+    __tablename__ = 'annotation'
+
+    id = Column(Integer, primary_key=True)
+    long_descr = Column(Text)
+    json_metadata = Column(Text)
+    short_descr = Column(String(500))
+
+
+class Dashboard(Base):
+    __tablename__ = 'dashboards'
+
+    id = Column(Integer, primary_key=True)
+    css = Column(Text)
+    dashboard_title = Column(String(500))
+    description = Column(Text)
+    json_metadata = Column(Text)
+    position_json = Column(MediumText())
+    slug = Column(String(255))
+
+
+class Database(Base):
+    __tablename__ = 'dbs'
+
+    id = Column(Integer, primary_key=True)
+    database_name = Column(String(250))
+    extra = Column(Text)
+    force_ctas_schema = Column(String(250))
+    sqlalchemy_uri = Column(String(1024))
+    verbose_name = Column(String(250))
+
+
+class DruidCluster(Base):
+    __tablename__ = 'clusters'
+
+    id = Column(Integer, primary_key=True)
+    broker_host = Column(String(255))
+    broker_endpoint = Column(String(255))
+    cluster_name = Column(String(250))
+    verbose_name = Column(String(250))
+
+
+class DruidColumn(BaseColumnMixin, Base):
+    __tablename__ = 'columns'
+
+    dimension_spec_json = Column(Text)
+
+
+class DruidDatasource(BaseDatasourceMixin, Base):
+    __tablename__ = 'datasources'
+
+    datasource_name = Column(String(255))
+    default_endpoint = Column(Text)
+    fetch_values_from = Column(String(100))
+
+
+class DruidMetric(BaseMetricMixin, Base):
+    __tablename__ = 'metrics'
+
+    json = Column(Text)
+
+
+class Slice(Base):
+    __tablename__ = 'slices'
+
+    id = Column(Integer, primary_key=True)
+    description = Column(Text)
+    params = Column(Text)
+    slice_name = Column(String(250))
+    viz_type = Column(String(250))
+
+
+class SqlaTable(BaseDatasourceMixin, Base):
+    __tablename__ = 'tables'
+
+    default_endpoint = Column(MediumText())
+    fetch_values_predicate = Column(String(1000))
+    main_dttm_col = Column(String(250))
+    schema = Column(String(255))
+    sql = Column(Text)
+    table_name = Column(String(250))
+    template_params = Column(Text)
+
+
+class SqlMetric(BaseMetricMixin, Base):
+    __tablename__ = 'sql_metrics'
+
+    expression = Column(Text)
+
+
+class TableColumn(BaseColumnMixin, Base):
+    __tablename__ = 'table_columns'
+
+    database_expression = Column(String(255))
+    expression = Column(Text)
+    python_date_format = Column(String(255))
+
+
+def upgrade():
+    bind = op.get_bind()
+    session = db.Session(bind=bind)
+
+    tables = [
+        Annotation,
+        Dashboard,
+        Database,
+        DruidCluster,
+        DruidColumn,
+        DruidDatasource,
+        DruidMetric,
+        Slice,
+        SqlaTable,
+        SqlMetric,
+        TableColumn,
+    ]
+
+    for table in tables:
+        for record in session.query(table).all():
+            for col in record.__table__.columns.values():
+                if not col.primary_key:
+                    if getattr(record, col.name) == '':
+                        setattr(record, col.name, None)
+
+        session.commit()
+
+    session.close()
+
+
+def downgrade():
+    pass