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validation_utils.py
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107 lines (89 loc) · 3.74 KB
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#!/usr/bin/env python3
# Copyright 2017 Google Inc. All Rights Reserved.
#
# Licensed 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.
"""Utilities for schema and command line validation"""
import argparse
import re
# For easier development, we allow redefining builtins like
# --substitutions=PROJECT_ID=foo even though gcloud doesn't.
KEY_VALUE_REGEX = re.compile(r'^([A-Z_][A-Z0-9_]*)=(.*)$')
def get_field_value(container, field_name, field_type):
"""Fetch a field from a container with typechecking and default values.
The field value is coerced to the desired type. If the field is
not present, an instance of `field_type` is constructed with no
arguments and used as the default value.
This function exists because yaml parsing can lead to surprising
outputs, and the resulting errors are confusing. For example:
entrypoint1: a string, but I can accidentally treat as an sequence
entrypoint2: [a, list, but, I, might, think, its, a, string]
version1: 3 # Parsed to int
version2: 3.1 # Parsed to float
version3: 3.1.1 # Parsed to str
feature: off # Parsed to the boolean False
Args:
container (dict): Object decoded from yaml
field_name (str): Field that should be present in `container`
field_type (type): Expected type for field value
Returns:
Any: Fetched or default value of field
Raises:
ValueError: if field value cannot be converted to the desired type
"""
try:
value = container[field_name]
if value is None:
return field_type()
except (IndexError, KeyError):
return field_type()
msg = 'Expected "{}" field to be of type "{}", but found type "{}"'
if not isinstance(value, field_type):
# list('some string') is a successful type cast as far as Python
# is concerned, but doesn't exactly produce the results we want.
# We have a whitelist of conversions we will attempt.
whitelist = (
(float, str),
(int, str),
(str, float),
(str, int),
(int, float),
)
if (type(value), field_type) not in whitelist:
raise ValueError(msg.format(field_name, field_type, type(value)))
try:
value = field_type(value)
except ValueError as e:
e.message = msg.format(field_name, field_type, type(value))
raise
return value
def validate_arg_regex(flag_value, flag_regex):
"""Check a named command line flag against a regular expression"""
if not re.match(flag_regex, flag_value):
raise argparse.ArgumentTypeError(
'Value "{}" does not match pattern "{}"'.format(
flag_value, flag_regex.pattern))
return flag_value
def validate_arg_dict(flag_value):
"""Parse a command line flag as a key=val,... dict"""
if not flag_value:
return {}
entries = flag_value.split(',')
pairs = []
for entry in entries:
match = re.match(KEY_VALUE_REGEX, entry)
if not match:
raise argparse.ArgumentTypeError(
'Value "{}" should be a list like _KEY1=value1,_KEY2=value2"'.
format(flag_value))
pairs.append((match.group(1), match.group(2)))
return dict(pairs)