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87 lines
2.9 KiB
Markdown
87 lines
2.9 KiB
Markdown
---
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name: library-logger-is-enabled
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group: api
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category: facade
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update-time: 20260613
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description: Check whether a LibraryLogger facade passes the wrapped logger's min-level gate for a given severity.
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key-word:
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- library
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- facade
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- enabled
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- public
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---
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## Library-logger-is-enabled
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Check whether a `LibraryLogger[S]` would accept a record at the given level based on its current `min_level`. This is the library-facing counterpart to `Logger::is_enabled(...)` and is useful for gating expensive message preparation.
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### Interface
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```moonbit
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pub fn[S] LibraryLogger::is_enabled(self : LibraryLogger[S], level : Level) -> Bool {
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```
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#### input
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- `self : LibraryLogger[S]` - Library-facing logger whose current minimum level should be checked.
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- `level : Level` - Candidate severity to test.
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#### output
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- `Bool` - `true` when the level is enabled by the facade's current threshold.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- This method delegates directly to the wrapped logger's `is_enabled(...)` behavior.
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- It only checks logger-level severity gating through `min_level`; it does not evaluate later sink filters, patch logic, or any sink-side buffering/wrapping behavior.
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- The result reflects the current wrapped logger state, so derived facades with different thresholds can return different answers.
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- This check does not require unwrapping because it is part of the narrower library-facing surface.
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- Use it when message construction or field gathering is expensive enough to justify a pre-check.
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### How to Use
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Here are some specific examples provided.
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#### When Avoid Expensive Library Debug Preparation
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When debug data should only be built if needed:
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```moonbit
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if logger.is_enabled(Level::Debug) {
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logger.info(build_summary())
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}
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```
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In this example, expensive preparation is skipped unless the current threshold allows that severity.
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#### When Inspect Effective Facade Threshold
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When package code should branch based on current logger behavior:
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```moonbit
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if logger.is_enabled(Level::Info) {
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logger.info("library path active")
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}
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```
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In this example, the check mirrors the same severity gate used by later write calls.
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And a `true` result still means only that the level gate passed, not that the record is guaranteed to survive later sink-side filtering or routing.
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### Error Case
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e.g.:
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- If `level` is below the current minimum threshold, the method returns `false`.
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- A `true` result does not guarantee final sink output if later filter logic rejects the record.
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- If callers need broader composition helpers rather than just the level gate, they must unwrap first with `to_logger()`.
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### Notes
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1. This is a cheap severity check, not a full end-to-end delivery guarantee.
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2. Prefer using it only when precomputing the log payload is meaningfully expensive.
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3. Use `log(...)` or the severity shortcuts directly when no expensive precomputation needs to be avoided.
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