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Nanaloveyuki
78 lines
2.0 KiB
Markdown
78 lines
2.0 KiB
Markdown
---
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name: redact-field
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group: api
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category: patching
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update-time: 20260512
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description: Create a reusable record patch that redacts one field key.
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key-word:
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- patch
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- redact
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- fields
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- public
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---
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## Redact-field
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Create a `RecordPatch` that replaces the value of every field whose key matches the given key. Use it when one sensitive field must be masked before records reach sinks.
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### Interface
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```moonbit
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pub fn redact_field(key : String, placeholder~ : String = "***") -> RecordPatch {}
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```
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#### input
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- `key : String` - Field key whose matching values should be replaced.
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- `placeholder : String` - Replacement value written into each matching field.
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#### output
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- `RecordPatch` - Patch that returns a record with matching field values redacted.
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### Explanation
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Detailed rules explaining key parameters and behaviors
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- The patch maps over the full field list and rewrites each field whose key equals `key`.
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- Non-matching fields are preserved unchanged.
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- All matching entries are redacted, not just the first one.
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- The default placeholder is `"***"`, but callers can provide a different mask string.
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### How to Use
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Here are some specific examples provided.
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#### When Mask One Sensitive Field
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When authentication logs may carry a token:
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```moonbit
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let logger = Logger::new(console_sink(), target="auth")
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.with_patch(redact_field("token"))
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```
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In this example, every `token` field value is replaced before output.
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#### When Use A Custom Placeholder
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When compliance rules require a specific visible marker:
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```moonbit
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let patch = redact_field("password", placeholder="[redacted]")
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```
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In this example, matching field values become `[redacted]` instead of the default mask.
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### Error Case
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e.g.:
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- If the record has no matching field key, the patch returns a structurally identical field list.
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- If `placeholder` is empty, matching values are replaced by an empty string.
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### Notes
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1. This helper only rewrites fields; it does not search message text.
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2. Use `redact_fields(...)` when several keys should share the same masking rule.
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