Ruby » Ruby master

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' # This is the root cause 
   rescue => a 
     begin 
       raise 'b' 
     rescue => b 
       begin 
         raise 'c' # This is the outermost cause assigned to `e` 
       rescue => c 
         c 
       end 
     end 
   end 
  
 p(e)                     # => #<RuntimeError: c> 
 p(e.cause)               # => #<RuntimeError: b> 
 p(e.cause.cause)         # => #<RuntimeError: a> 
 p(e.cause.cause.cause) # => nil 

 p(e.root_cause)          # => #<RuntimeError: 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

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