Runtime-sink-file-default-policy-or-none

Read the default runtime file policy from a RuntimeSink only when it is actually file-backed.

The returned FileSinkPolicy value is owned by src/file_model; this method belongs to the runtime facade layer and avoids fabricating that model on non-file variants.

This is the truthful companion to file_default_policy(). Prefer it when default-policy inspection should not fabricate a fallback object on non-file sinks.

Interface

pub fn RuntimeSink::file_default_policy_or_none(self : RuntimeSink) -> FileSinkPolicy? {

input

• self : RuntimeSink - Runtime sink whose default file policy should be inspected.

output

• FileSinkPolicy? - Some(policy) when the runtime sink is file-backed, otherwise None.

Explanation

Detailed rules explaining key parameters and behaviors

• Plain File runtime variants return Some(default_policy).
• QueuedFile runtime variants forward the wrapped inner file sink default policy as Some(default_policy).
• The wrapped value is the shared @file_model.FileSinkPolicy model, not a runtime-owned concrete type.
• Non-file runtime variants return None.
• This helper is useful when callers need to compare runtime drift or restore defaults without fabricating file semantics.

How to Use

Here are some specific examples provided.

When Need Truthful Baseline Policy Visibility

When tooling should inspect defaults only for real file-backed sinks:

let defaults = sink.file_default_policy_or_none()

In this example, None means the runtime sink has no file default policy.

When Compare Current And Default Policy Truthfully

When diagnostics should avoid fallback policy objects:

match (sink.file_policy_or_none(), sink.file_default_policy_or_none()) {
  (Some(current), Some(defaults)) => ignore((current, defaults))
  _ => ()
}

In this example, comparisons happen only when real file semantics exist.

Error Case

e.g.:

• If the runtime sink is not file-backed, the method returns None.

• If callers only need a drift boolean, file_policy_matches_default() remains simpler.

Notes

1. Prefer this helper over file_default_policy() for truthful runtime diagnostics.

2. file_default_policy() remains available as the compatibility fallback API.