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Move some utility functions into their own file
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Doug Greiman
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Jun 16, 2017
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,98 @@ | ||
| #!/usr/bin/env python3 | ||
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| # 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. | ||
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| """Utilities for schema and command line validation""" | ||
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| import argparse | ||
| import re | ||
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| # 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_]*)=(.*)$') | ||
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| 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, a instance of `field_type` is constructed with no | ||
| arguments and used as the default value. | ||
| 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() | ||
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| 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))) | ||
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| try: | ||
| value = field_type(value) | ||
| except ValueError as e: | ||
| e.message = msg.format(field_name, field_type, type(value)) | ||
| raise | ||
| return value | ||
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| 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 | ||
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| 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) |
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