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Nanaloveyuki
84 lines
2.2 KiB
Markdown
84 lines
2.2 KiB
Markdown
---
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name: logger-with-min-level
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group: api
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category: logging
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update-time: 20260512
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description: Replace the logger minimum enabled level so lower-severity records are skipped earlier.
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key-word:
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- logger
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- level
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- filter
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- public
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---
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## Logger-with-min-level
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Replace the logger's minimum enabled level. This API controls the first gate checked by `log(...)` and the convenience level methods.
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### Interface
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```moonbit
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pub fn[S] Logger::with_min_level(self : Logger[S], min_level : Level) -> Logger[S] {}
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```
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#### input
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- `self : Logger[S]` - Base logger whose level threshold should change.
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- `min_level : Level` - New minimum enabled level.
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#### output
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- `Logger[S]` - A new logger value carrying the updated threshold.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- `log(...)` checks `is_enabled(level)` before constructing and writing a record.
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- Lower-severity records below `min_level` are skipped without reaching the sink.
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- This API replaces the logger threshold and does not add a wrapper sink.
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- The returned logger keeps the same sink, target, and timestamp settings.
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### How to Use
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Here are some specific examples provided.
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#### When Raise Noise Floor In Production
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When only warning and error records should be emitted:
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```moonbit
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let logger = Logger::new(console_sink())
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.with_min_level(Level::Warn)
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```
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In this example, `trace`, `debug`, and `info` calls are skipped.
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#### When Derive A More Verbose Local Logger
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When one branch of code should keep a different threshold:
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```moonbit
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let base = Logger::new(console_sink(), min_level=Level::Info)
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let debug_logger = base.with_min_level(Level::Debug)
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```
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In this example, the sink is reused while the threshold changes per logger value.
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### Error Case
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e.g.:
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- If `min_level` is set too high, expected lower-severity diagnostics may disappear.
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- If callers need richer predicate logic than a simple threshold, `with_filter(...)` should be used instead.
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### Notes
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Notes are here.
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1. This API is the cheapest built-in severity gate.
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2. Use it before adding more complex filtering rules.
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3. It composes cleanly with target, patch, and context-field helpers.
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4. The original logger is unchanged because a new value is returned.
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