📝 补充runtime文档

docs/api/runtime-sink-flush.md

@@ -2,8 +2,8 @@
 name: runtime-sink-flush
 group: api
 category: runtime
-update-time: 20260613
-description: Flush a RuntimeSink and return how many queued or file-backed operations were advanced.
+update-time: 20260707
+description: Compatibility RuntimeSink flush helper that still returns one Int by collapsing generic queue progress and plain-file fallback steps.
 key-word:
     - runtime
     - sink
@@ -13,7 +13,7 @@ key-word:
 
 ## Runtime-sink-flush
 
-Flush a `RuntimeSink` and return how much work was advanced. This is the direct runtime control API behind configured logger flush behavior.
+Flush a `RuntimeSink` and return one compatibility count. This helper is still available for older code, but new generic runtime code should prefer `flush_progress()` because it exposes queue advancement and plain-file fallback steps separately.
 
 ### Interface
 
@@ -27,16 +27,18 @@ pub fn RuntimeSink::flush(self : RuntimeSink) -> Int {
 
 #### output
 
-- `Int` - Count of advanced operations as reported by the concrete runtime sink variant.
+- `Int` - Compatibility count produced from the structured `flush_progress()` result.
 
 ### Explanation
 
 Detailed rules explaining key parameters and behaviors
 
-- Plain console-style runtime sinks return `0` because they do not keep explicit buffered flush state here.
-- Plain file runtime sinks call `FileSink::flush()` and convert the boolean result into `1` or `0`.
-- Queue-wrapped runtime sinks forward to the wrapped queue sink's `flush()` behavior.
-- This method is the direct sink-level API used by `ConfiguredLogger::flush(...)`.
+- This method now delegates to `flush_progress()` and sums `queue_advanced_count + file_flush_step_count` back into one compatibility number.
+- Plain console-style runtime sinks still return `0` because the structured result stays zeroed.
+- Plain file runtime sinks still expose their generic fallback through `1` or `0`, but that value now comes from `file_flush_step_count` in the structured result.
+- Queue-wrapped runtime sinks still return the number of queued records consumed during that flush.
+- For queued file sinks, a positive returned count still means queue advancement, not a durable file-write count.
+- This method remains the direct sink-level API used by `ConfiguredLogger::flush(...)`.
 
 ### How to Use
 
@@ -44,33 +46,39 @@ Here are some specific examples provided.
 
 #### When Need Direct Runtime Flush Control
 
-When code is working with a `RuntimeSink` value directly instead of going through `ConfiguredLogger`:
+When older code is already built around one numeric flush count:
 ```moonbit
 let flushed = sink.flush()
 ```
 
-In this example, the runtime sink reports how much flush work was advanced.
+In this example, the runtime sink still reports one compatibility count.
 
 #### When Need Queue Or File Progress Visibility
 
-When support code should observe whether a direct flush request did useful work:
+When code only needs a coarse non-zero check and does not care which runtime dimension advanced:
 ```moonbit
 if sink.flush() > 0 {
   ()
 }
 ```
 
-In this example, the return value reflects whether queue draining or file flushing advanced any work.
+In this example, the count still reflects generic runtime advancement, not durable file success.
 
 ### Error Case
 
 e.g.:
 - If the runtime sink shape has no flushable state, the method may simply return `0`.
 
-- If callers need bounded queue progress, `drain(...)` is the better API.
+- If callers need truthful generic progress semantics, `flush_progress()` is the better API.
+
+- If callers need bounded queue progress, `drain_progress(...)` is usually the better API.
+
+- If callers need file-specific success semantics on a file-backed sink, `file_flush()` is the better API.
 
 ### Notes
 
-1. Use this helper when direct runtime sink flushing matters.
+1. Treat this method as a compatibility helper for older numeric code.
 
-2. `ConfiguredLogger::flush(...)` is the higher-level wrapper for config-built loggers.
+2. Prefer `flush_progress()` in new generic runtime code.
+
+3. `ConfiguredLogger::flush(...)` is the higher-level wrapper for config-built loggers.