Feature #19197
Updated by AMomchilov (Alexander Momchilov) almost 2 years ago
### Description
I would like to add a `#root_cause` method to `Exception`.
It returns the last exception in linked-list of causality chain, that is, the original exception (whose own `cause` is `nil`).
### Example
```ruby
e = begin
raise 'A' 'a' # This is the root cause
rescue => a
begin
raise 'B' 'b'
rescue => B b
begin
raise 'C' 'c' # This is the outermost cause assigned to `e`
rescue => c
c
end
end
end
# Here's what the structure looks like:
# C -> B -> A -> nil
p(e) # => #<RuntimeError: C> c>
p(e.cause) # => #<RuntimeError: B> b>
p(e.cause.cause) # => #<RuntimeError: A> a>
p(e.cause.cause.cause) # => nil
# Here's the proposed API, showing that A is the root cause of e
p(e.root_cause) # => #<RuntimeError: A>
# And that the root_cause has no further cause a>
p(e.root_cause.cause) # => nil
```
### Motivation
There are some kinds of exceptions that can occur all over the place (and might be wrapped by arbitrarily many middlemen), but are attributable to a singular global cause. For example, a database outage could raise exceptions in almost every line of business logic of an app that uses ActiveRecord models.
Fundamentally, you wouldn't want an error report for every one of these lines. You'd want to look at the root cause, and bucket all SQL-connection issues into a single report, regardless of where they surface.
### Implementation
Draft PR: https://github.com/ruby/ruby/pull/6913