src/NLog/Targets/ConsoleWordHighlightingRule.cs (3)

252-282: GenerateMatch: correct trimming; consider EOL symmetry and delimiter-only intent

The trimming logic is sound and produces the desired “word-only” highlight from a delimited needle.

Two follow-ups to consider:

• Symmetry with end-of-line: The current acceptance logic in FindNextWordForHighlighting accounts for start-of-line but not end-of-line when only one side has a delimiter. If you also want to support patterns like "Warn|" at end-of-message (WholeWords), see my suggestion on Lines 305-309.
• Delimiter-only needles: When the needle consists entirely of non-letter/digit characters, this returns the original span (highlights only delimiters). Verify that this is intentional with “WholeWords” semantics. If not, you might choose to skip these matches.

Performance (optional): GenerateMatch rescans the same needle each time it’s called. When there are many occurrences, precomputing trim offsets per needle can avoid repeated scans.

Do you want delimiter-only needles to be highlighted under WholeWords, or should they be skipped entirely? I can provide a targeted change and unit test if you want to change this behavior.

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286-286: Consistent use of GenerateMatch; consider precomputing trim once per needle

LGTM on switching all yields to GenerateMatch to ensure consistent trimming when WholeWords is enabled.

Optional improvement: precompute the left-trim count and core length once per needle and reuse them across calls to avoid rescanning in GenerateMatch for every match occurrence. If you’d like, I can propose a small helper (e.g., ComputeWordSpan) and wire it here.

Also applies to: 288-288, 295-295

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305-309: WholeWords boundary: add end-of-line symmetry for one-sided delimiters

The added condition allows delimited needles like “|Warn|” (or “at ” at index 0) to pass WholeWords checks. To handle the symmetric case at the end of the haystack (e.g., “|Warn” at end-of-message), consider also treating end-of-line as a valid non-word boundary.

Suggested change:

-                if (StringHelpers.IsWholeWord(haystack, needle, index) || ((index == 0 || !char.IsLetterOrDigit(needle[0])) && !char.IsLetterOrDigit(needle[needle.Length - 1])))
+                var startBoundaryOk = (index == 0) || !char.IsLetterOrDigit(needle[0]);
+                var endBoundaryOk = (index + needle.Length == haystack.Length) || !char.IsLetterOrDigit(needle[needle.Length - 1]);
+                if (StringHelpers.IsWholeWord(haystack, needle, index) || (startBoundaryOk && endBoundaryOk))
                     return index;

This keeps the current behavior for “|Warn|” and also supports start-only or end-only delimiter cases at the message boundaries.

If only “both-sides delimited” needles (like “|Warn|”) are intended, and one-sided cases should be ignored, please disregard this suggestion. Otherwise, I can add unit tests for start-only and end-only delimiter scenarios.

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