[Resolve #1468] Cast parameters to strings

[alex-harvey-z3q]

In already-resolved and merged issue #1443 we implemented parameter validation.

Subsequent discussion led to a consensus that it would be better to not only validate parameters, but also cast where applicable to string. This will lead to a cleaner user experience for most Sceptre users where parameters passed as ints, floats and bools in their YAML values files are cast to strings first and then sent to CloudFormation, since CloudFormation's API is unable to handle other types.

This PR changes the _ensure_parameters method to _cast_parameters in the Stack class to handle casting to strings where applicable instead of only validating.

PR Checklist

• Wrote a good commit message & description [see guide below].
• Commit message starts with [Resolve #issue-number].
• Added/Updated unit tests.
• Added/Updated integration tests (if applicable).
• All unit tests (poetry run tox) are passing.
• Used the same coding conventions as the rest of the project.
• The new code passes pre-commit validations (poetry run pre-commit run --all-files).
• The PR relates to only one subject with a clear title.
  and description in grammatically correct, complete sentences.

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• Before merge squash related commits.

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[zaro0508]

In already-resolved and merged issue #1443 we implemented parameter validation.

the PR for that issue was not merged?

Otherwise, in general this PR LGTM but would like the method to be more concise and clear.

[alex-harvey-z3q]

the PR for that issue was not merged?

It was merged in f3b7e51 but we have never released those changes thus no users will be impacted by this change to the earlier implementation (unless they are consuming the master branch).

[zaro0508]

thanks for the clarification

[fen9li]

Hey Alex,

Good day. I received an error may have something to do with this merge.

My config/bla-bla/config.yaml file looks like below:

---
sceptre_role: <aws-role-arn>

environment: bla-bla
application: bla-bla
accountid: <aws-account-id>
instance_type: t3.large
db_instance_type: db.t3.small
license_model: license-included
db_storage: '40'
multi_az: 'false'
restore_db_snapshot_identifier: 'null'

stack_tags_env:
  xxxxxx: xxxxxx

The error:

[2024-09-09T12:43:16.398Z] + sceptre --var-file config/config.yaml --var-file config/bla-bla/config.yaml launch -y bla-bla

[2024-09-09T12:43:16.964Z] "bla-bla/rds-instances: Values for parameters must be strings, lists or resolvers, got {'Environment': 'bla-bla', 'Application': 'bla-bla', 'RDSMasterUser': <username>, 'RDSMasterUserPassword': <password>, 'InstanceType': 'db.t3.small', 'LicenseModel': 'license-included', 'AllocatedStorageGB': '40', 'MultiAZ': 'false', 'RestoreDBSnapshotIdentifier': None}"

script returned exit code 1

I reckon that the string 'null' in my config/bla-bla/config.yaml somehow converted to None and failed the new added validation. Any chance to add one more test {"NullAsString": "null"}, here:

 "parameters",
        [
            {"IntAsString": "1"},
            {"Int": 1},
            {"BoolAsString": "true"},
            {"Bool": True},
            {"List": ["aStringAndA", FakeResolver()]},
            {"ListOfInts": [1, 2, 3]},
            {"Resolver": FakeResolver()},
        ],

So we can know if there is any bug here? Thank you very much.
Feng

[fen9li]

Hey Alex,

I fixed the issue already. Need adding "" to the value when passed down like below.

 RestoreDBSnapshotIdentifier: "{{ var.restore_db_snapshot_identifier }}"

Thanks.
Feng