A Normalizing Plan Modifier Turns Other Computed Attributes Unknown

Trigger: terraform plan never comes back empty. It reports ~ some_attr = (known after apply) for an attribute absent from HCL, while the attribute that actually differs renders as unchanged. Applying does not converge. In this repo it was coralogix_dashboard.auto_refresh next to access_policy.

Cause: MarkComputedNilsAsUnknown (fwserver/server_planresourcechange.go) runs when PlannedState.Raw != PriorState.Raw anywhere, and it replaces the value of every attribute that is Computed, null in config, and has no Default — it never checks the planned value, so a known value is overwritten too. It runs before attribute plan modifiers, so a modifier that hides the difference later (PreserveStateForEquivalentJSON pinning the state's JSON text) cannot undo the marking. State text and config text never converge, so the raw difference is permanent.

Fix, pick one:

• Root: let state adopt the config text, so proposed == prior after one apply. Costs a one-time cosmetic diff when only formatting or key order changed.
• Local: plan a known value for the collateral attribute — but only where the provider guarantees the post-apply value. content_json guarantees null via the flatten path, so NullWhenContentJSONManaged plans null. Where the backend decides, unknown is the only correct plan; a known value risks "Provider produced inconsistent result after apply".

Do not use plain UseStateForUnknown() as the local fix. It copies the prior value, so removing the attribute from HCL stops resetting it.

Check first: attributes with a Default and attributes with a restoring modifier (id, via UseStateForUnknown) are immune — that is why only one attribute appears in the diff.