BitLogger/docs/api/redact-field.md

name, group, category, update-time, description, key-word

name	group	category	update-time	description	key-word
redact-field	api	patching	20260512	Create a reusable record patch that redacts one field key.	patch redact fields public

Redact-field

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.

Interface

pub fn redact_field(key : String, placeholder~ : String = "***") -> RecordPatch {}

input

• key : String - Field key whose matching values should be replaced.
• placeholder : String - Replacement value written into each matching field.

output

• RecordPatch - Patch that returns a record with matching field values redacted.

Explanation

Detailed rules explaining key parameters and behaviors

• The patch maps over the full field list and rewrites each field whose key equals key.
• Non-matching fields are preserved unchanged.
• All matching entries are redacted, not just the first one.
• The default placeholder is "***", but callers can provide a different mask string.

How to Use

Here are some specific examples provided.

When Mask One Sensitive Field

When authentication logs may carry a token:

let logger = Logger::new(console_sink(), target="auth")
  .with_patch(redact_field("token"))

In this example, every token field value is replaced before output.

When Use A Custom Placeholder

When compliance rules require a specific visible marker:

let patch = redact_field("password", placeholder="[redacted]")

In this example, matching field values become [redacted] instead of the default mask.

Error Case

e.g.:

• If the record has no matching field key, the patch returns a structurally identical field list.

• If placeholder is empty, matching values are replaced by an empty string.

Notes

1. This helper only rewrites fields; it does not search message text.

2. Use redact_fields(...) when several keys should share the same masking rule.