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Nanaloveyuki
80 lines
2.1 KiB
Markdown
80 lines
2.1 KiB
Markdown
---
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name: level-at-least
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group: api
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category: filtering
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update-time: 20260512
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description: Create a reusable record predicate that keeps records at or above a minimum level.
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key-word:
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- level
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- filter
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- predicate
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- public
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---
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## Level-at-least
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Create a `RecordPredicate` that returns `true` when a record level is greater than or equal to a minimum threshold. This is the main helper for severity-based filtering.
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### Interface
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```moonbit
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pub fn level_at_least(min_level : Level) -> RecordPredicate {}
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```
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#### input
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- `min_level : Level` - The lowest level that should remain enabled.
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#### output
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- `RecordPredicate` - Predicate that keeps records whose `priority()` is at least the given minimum.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- Matching is based on `Level::priority()`, not string comparison.
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- Records at the exact same level as `min_level` are included.
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- This helper is useful when a sink or child logger needs a stricter threshold than the parent logger.
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- It composes cleanly with `all_of(...)` and `any_of(...)`.
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### How to Use
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Here are some specific examples provided.
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#### When Keep Warnings And Errors
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When a logger should keep only important records:
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```moonbit
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let logger = Logger::new(console_sink())
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.with_filter(level_at_least(Level::Warn))
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```
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In this example, `Warn` and `Error` records continue through the filter.
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#### When Combine With Target Routing
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When both severity and namespace matter:
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```moonbit
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let predicate = all_of([
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target_has_prefix("service.api"),
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level_at_least(Level::Info),
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])
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```
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In this example, the predicate can be reused by multiple loggers or sinks.
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### Error Case
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e.g.:
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- If `min_level` is `Level::Trace`, the predicate effectively allows all normal log records.
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- If `min_level` is higher than the record level, the predicate returns `false` without modifying the record.
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### Notes
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1. Use this helper when you want filtering logic to remain explicit instead of embedding level checks inline.
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2. This predicate is separate from a logger's own `min_level`, so both can be combined.
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