📝 document file sink policy mutators

docs/api/file-sink-clear-rotation.md

@@ -0,0 +1,71 @@
+---
+name: file-sink-clear-rotation
+group: api
+category: sink
+update-time: 20260613
+description: Disable runtime rotation on a FileSink.
+key-word:
+    - file
+    - sink
+    - rotation
+    - public
+---
+
+## File-sink-clear-rotation
+
+Disable runtime rotation on a `FileSink`. This helper is the direct shortcut for clearing rotation policy on the concrete sink.
+
+### Interface
+
+```moonbit
+pub fn FileSink::clear_rotation(self : FileSink) -> Unit {
+```
+
+#### input
+
+- `self : FileSink` - File sink whose rotation policy should be cleared.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This method removes the current rotation policy by setting it to `None`.
+- It changes stored policy only and does not reopen the file.
+- Current append and auto-flush settings are left unchanged.
+- This helper is equivalent in intent to a broader setter with `None`, but is clearer at the call site.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need To Disable Rotation Explicitly
+
+When direct runtime file rotation should be turned off:
+```moonbit
+sink.clear_rotation()
+```
+
+In this example, rotation policy is removed directly from the sink.
+
+#### When Need A Clear Intent Shortcut
+
+When code should make the disable-rotation intent obvious:
+```moonbit
+sink.clear_rotation()
+ignore(sink.rotation_enabled())
+```
+
+In this example, the call site reads more clearly than using a broader policy setter.
+
+### Error Case
+
+e.g.:
+- If callers need to switch to another rotation config rather than disable rotation, `set_rotation(...)` is the better API.
+
+- This helper does not report past rotation failures; use `rotation_failures()` or `state()` for diagnostics.
+
+### Notes
+
+1. Use this helper when the desired effect is simply “rotation off”.
+
+2. It is clearer than passing `None` through a broader setter when intent matters.

docs/api/file-sink-set-append-mode.md

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+---
+name: file-sink-set-append-mode
+group: api
+category: sink
+update-time: 20260613
+description: Update the append-mode policy used by a FileSink for later reopen behavior.
+key-word:
+    - file
+    - sink
+    - append
+    - public
+---
+
+## File-sink-set-append-mode
+
+Update the append-mode policy used by a `FileSink`. This helper changes future reopen behavior on the concrete sink without forcing an immediate reopen.
+
+### Interface
+
+```moonbit
+pub fn FileSink::set_append_mode(self : FileSink, append : Bool) -> Unit {
+```
+
+#### input
+
+- `self : FileSink` - File sink whose append-mode policy should change.
+- `append : Bool` - New append-mode policy.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This method updates stored policy only.
+- It does not force an immediate reopen.
+- The new value affects later reopen behavior.
+- The sink path and current rotation policy are left unchanged.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need To Change Future Reopen Behavior
+
+When direct recovery code should later prefer append mode explicitly:
+```moonbit
+sink.set_append_mode(true)
+```
+
+In this example, later reopen operations use the updated append policy.
+
+#### When Want To Separate Policy Mutation From Reopen Timing
+
+When code should update policy now and reopen later:
+```moonbit
+sink.set_append_mode(false)
+ignore(sink.reopen_with_current_policy())
+```
+
+In this example, policy mutation and reopen timing remain separate decisions.
+
+### Error Case
+
+e.g.:
+- If callers need an immediate reopen as part of the same operation, one of the reopen helpers should be used afterward.
+
+- This method does not itself prove that the sink is currently available or writable.
+
+### Notes
+
+1. This helper changes stored policy, not live file-handle state by itself.
+
+2. It is useful when direct file-sink recovery logic wants to stage reopen behavior in advance.

docs/api/file-sink-set-auto-flush.md

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+---
+name: file-sink-set-auto-flush
+group: api
+category: sink
+update-time: 20260613
+description: Update the auto-flush policy used by a FileSink.
+key-word:
+    - file
+    - sink
+    - flush
+    - public
+---
+
+## File-sink-set-auto-flush
+
+Update the auto-flush policy used by a `FileSink`. This helper changes direct runtime durability behavior without rebuilding the sink.
+
+### Interface
+
+```moonbit
+pub fn FileSink::set_auto_flush(self : FileSink, enabled : Bool) -> Unit {
+```
+
+#### input
+
+- `self : FileSink` - File sink whose auto-flush policy should change.
+- `enabled : Bool` - New auto-flush setting.
+
+### Explanation
+
+Detailed rules explaining key parameters and behaviors
+
+- This method updates runtime policy only.
+- It does not itself flush pending data.
+- The new value affects whether later writes attempt a flush after each rendered record.
+- Existing path, append policy, and rotation policy are left unchanged.
+
+### How to Use
+
+Here are some specific examples provided.
+
+#### When Need Direct Durability Tuning
+
+When a concrete file sink should start flushing each write automatically:
+```moonbit
+sink.set_auto_flush(true)
+```
+
+In this example, runtime policy is updated without rebuilding the sink.
+
+#### When Need To Relax Flush Pressure
+
+When a file sink should stop auto-flushing for throughput reasons:
+```moonbit
+sink.set_auto_flush(false)
+```
+
+In this example, the call site updates policy explicitly on the direct file sink.
+
+### Error Case
+
+e.g.:
+- If callers need an immediate flush action, `flush()` is the operational API.
+
+- This helper does not report whether previous writes or flushes succeeded.
+
+### Notes
+
+1. Use this helper for direct runtime durability tuning.
+
+2. Pair it with `auto_flush_enabled()` to verify the active policy.

docs/api/index.md

@@ -146,6 +146,9 @@ BitLogger API navigation.
 - [file-sink-path.md](./file-sink-path.md)
 - [file-sink-auto-flush-enabled.md](./file-sink-auto-flush-enabled.md)
 - [file-sink-rotation-enabled.md](./file-sink-rotation-enabled.md)
+- [file-sink-set-append-mode.md](./file-sink-set-append-mode.md)
+- [file-sink-set-auto-flush.md](./file-sink-set-auto-flush.md)
+- [file-sink-clear-rotation.md](./file-sink-clear-rotation.md)
 - [file-sink-type.md](./file-sink-type.md)
 - [native-files-supported.md](./native-files-supported.md)
 - [file-rotation.md](./file-rotation.md)