📝 Add configured logger file policy API docs

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Nanaloveyuki
2026-05-12 14:58:22 +08:00
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---
name: configured-logger-file-set-policy
group: api
category: runtime
update-time: 20260512
description: Apply a bundled runtime file policy update to a configured file-backed logger.
key-word:
- logger
- runtime
- file
- public
---
## Configured-logger-file-set-policy
Apply a bundled runtime file policy update to a `ConfiguredLogger`. This helper updates append mode, auto-flush, and rotation together through one runtime policy object.
### Interface
```moonbit
pub fn ConfiguredLogger::file_set_policy(self : ConfiguredLogger, policy : FileSinkPolicy) -> Bool {}
```
#### input
- `self : ConfiguredLogger` - Config-driven runtime logger whose file policy should change.
- `policy : FileSinkPolicy` - Bundled runtime file policy to apply.
#### output
- `Bool` - Whether the policy update was applied.
### Explanation
Detailed rules explaining key parameters and behaviors
- File-backed sinks update append, auto-flush, and rotation together.
- Queued file sinks forward the policy update to the wrapped file sink.
- Non-file sinks return `false`.
- This helper is broader than the single-setting setters because it updates the whole file policy in one call.
### How to Use
Here are some specific examples provided.
#### When Need Bundled Runtime Policy Changes
When append, flush, and rotation should change together:
```moonbit
ignore(logger.file_set_policy(FileSinkPolicy::new(
append=true,
auto_flush=false,
rotation=Some(file_rotation(2048, max_backups=2)),
)))
```
In this example, runtime file behavior is updated as one policy change.
#### When Apply A Policy Snapshot
When a previously captured or computed policy should be restored:
```moonbit
let ok = logger.file_set_policy(policy)
```
In this example, callers can reapply a whole policy object without splitting it into separate setter calls.
### Error Case
e.g.:
- If the configured sink is not file-backed, the method returns `false`.
- If callers only need to change one setting, a narrower setter such as `file_set_auto_flush(...)` or `file_set_rotation(...)` may be clearer.
### Notes
1. Use this helper when the runtime policy should be treated as one cohesive object.
2. It pairs naturally with `file_policy()` and `file_default_policy()`.