Scientists

Ideas for backwards-compatible solutions (none of them particularly clean):

ignore could pass more arguments to the block, which is backwards-compatible assuming clients use a proc.
Add a new method ignore2 which receives observation objects instead of values.
Pass a custom nil-value as observation value to ignore if an exception is raised. This special nil-value should expose the exception.

No files, tests, or entry points are named. Start by locating the ignore API and its handling of observation values and exceptions, then review the three backwards-compatible approaches in the issue. Done requires a maintainer-approved API choice and tests covering compatibility and exception visibility.

Written by the indexing model from the issue text.