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Nanaloveyuki
77 lines
2.1 KiB
Markdown
77 lines
2.1 KiB
Markdown
---
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name: record-with-target
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group: api
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category: record
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update-time: 20260613
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description: Return a copy of a record with a replaced target field.
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key-word:
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- record
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- target
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- transform
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- public
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---
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## Record-with-target
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Return a copy of a `Record` with a different `target`. This helper is the narrowest way to retarget one record value while preserving its level, message, timestamp, and fields.
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### Interface
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```moonbit
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pub fn Record::with_target(self : Record, target : String) -> Record {}
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```
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#### input
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- `self : Record` - Base record whose target should be replaced.
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- `target : String` - New target value for the returned record.
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#### output
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- `Record` - New record value carrying the updated target.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- This helper returns a new record value instead of mutating the original one.
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- Only the `target` field is replaced.
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- `level`, `message`, `timestamp_ms`, and `fields` are preserved.
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- This is useful for adapters, patches, or tests that need one explicit retargeted record value.
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### How to Use
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Here are some specific examples provided.
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#### When Need To Retarget One Existing Record
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When one record should be reclassified under a different namespace:
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```moonbit
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let rec = Record::new(Level::Info, "started", target="worker")
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let api_rec = rec.with_target("api")
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```
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In this example, only the returned record carries the new target.
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#### When Need Direct Value-level Rewriting In Tests
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When a formatter or filter test should exercise a different target without rebuilding the full record:
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```moonbit
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let rec = Record::new(Level::Warn, "retry").with_target("jobs.retry")
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```
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In this example, the retargeting stays local to one record value.
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### Error Case
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e.g.:
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- If `target` is empty, the returned record is still valid and simply carries an empty target.
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- If code should rewrite many records consistently, a reusable patch such as `set_target(...)` may be a better fit than calling this helper repeatedly.
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### Notes
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1. Use this helper for value-level retargeting of one record.
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2. Use `set_target(...)` when the same transformation should be reused as a `RecordPatch`.
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