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add UsePreviousValue support for parameters when updating a CloudFormation stack (#1504)

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Ben Jones 2018-03-21 11:13:05 -05:00 • committed by Jack Danger
commit c13f77173f
2 changed files with 37 additions and 3 deletions
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13
moto/cloudformation/responses.py
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@ -222,17 +222,24 @@ class CloudFormationResponse(BaseResponse):
role_arn = self._get_param('RoleARN')
template_url = self._get_param('TemplateURL')
stack_body = self._get_param('TemplateBody')
stack = self.cloudformation_backend.get_stack(stack_name)
if self._get_param('UsePreviousTemplate') == "true":
stack_body = self.cloudformation_backend.get_stack(
stack_name).template
stack_body = stack.template
elif not stack_body and template_url:
stack_body = self._get_stack_from_s3_url(template_url)
incoming_params = self._get_list_prefix("Parameters.member")
parameters = dict([
(parameter['parameter_key'], parameter['parameter_value'])
for parameter
in self._get_list_prefix("Parameters.member")
in incoming_params if 'parameter_value' in parameter
])
previous = dict([
(parameter['parameter_key'], stack.parameters[parameter['parameter_key']])
for parameter
in incoming_params if 'use_previous_value' in parameter
])
parameters.update(previous)
# boto3 is supposed to let you clear the tags by passing an empty value, but the request body doesn't
# end up containing anything we can use to differentiate between passing an empty value versus not
# passing anything. so until that changes, moto won't be able to clear tags, only update them.