Improve substitution recursion check #1720
Merged
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.

Creates SubstitutionStackError and trace recursion from
the beginning of substitution, allowing prevention of the
recursion to halt sooner, and avoid None in error message.
Related to #1716
Note this doesnt really fix anything that is user-facing, except inside the exception message that 90% of users will not read anyway.
So very low priority / optional. I dont have anything which depends on this area.
One reason to reject this is the amount of
git blamechanges is high for no actual benefit to the user, and very small benefit to developers.Contribution checklist:
(also see CONTRIBUTING.rst for details)
in message body
<issue number>.<type>.rstfor example (588.bugfix.rst)<type>is must be one ofbugfix,feature,deprecation,breaking,doc,misc<your username>"superuser."CONTRIBUTORS(preserving alphabetical order)