Pub/Sub - Change Allowed Persistence Regions to Set in 'google_pubsub_topic'

[abbrowne126]

Fixes hashicorp/terraform-provider-google#21650

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Change `google_pubsub_topic.allowed_persistence_regions` from `List` to `Set` type.

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[roaks3]

Per https://googlecloudplatform.github.io/magic-modules/breaking-changes/make-a-breaking-change/#in-minor-releases, this seems like it could qualify as a change for a minor release:

Changing a List to a Set where the field is unordered and the order returned from the API changes unpredictably.

Could you confirm if this issue occurs whenever the field is used, and that the order of elements is not predictable (ie. it can keep changing over time). Effectively, if these things are true, there is virtually no way someone would be able to use the field as a List.

[abbrowne126]

Per https://googlecloudplatform.github.io/magic-modules/breaking-changes/make-a-breaking-change/#in-minor-releases, this seems like it could qualify as a change for a minor release:

Changing a List to a Set where the field is unordered and the order returned from the API changes unpredictably.

Could you confirm if this issue occurs whenever the field is used, and that the order of elements is not predictable (ie. it can keep changing over time). Effectively, if these things are true, there is virtually no way someone would be able to use the field as a List.

I opened a PR as a minor release and was told to put it in the major release #13510

I can confirm this - there is a permadiff on this field, and additionally the field should be a set based on its behavior

[roaks3]

Ok, let me confirm with the team. This scenario falls in a bit of a grey area in that it is technically an "exception", but we have also precedence for including cases like this in a minor release.

[abbrowne126]

Sounds good, thank you Ryan. Just one question: I am guessing I shouldn't list it as a breaking change in the release notes if it goes into a minor release?