8. TODO regular expression pattern and file scanning

Date: 2026-04-22

Status

Accepted

Context

Cerebro must find TODO, Needs Fixing, Hack, and Placeholder comments reliably in source code while avoiding false positives.

Decision

Regex pattern:

(?i)\b(TODO|FIXME|HACK|XXX)\b[\s:]*(.*)$

Features:

• Case-insensitive matching using the (?i) flag
• Word boundary anchors using \b
• Captures keyword + optional text after : or whitespace

File scanning:

• Uses ignore::WalkBuilder to respect .gitignore
• Skips binary/non-source extensions (png, jpg, pdf, zip, etc.)

Sorting priority from highest to lowest covers Needs Fixing, then TODO, then Hack, then Placeholder.

Consequences

Pros

• Case-insensitive catches todo:, TODO:, Todo:
• Respects gitignore automatically
• Skips common false positives, such as minified JS and images

Cons

• Won’t catch multi-line comments
• Won’t catch TODO in strings without keyword prefix

Notes

See collectors/todos.rs for implementation.