Ruby » Ruby master

Feature #10481

Updated by nobu (Nobuyoshi Nakada) about 10 years ago

I'd like to propose a syntax change: allow boolean "if" and "unless" clauses to follow a rescue statement. 

 Consider the following: 

 ~~~ruby ~~~ 
 begin 
   ... 
 rescue SomeError => e 
   if e.error_code == 1 
     ...handle error... 
   else 
     raise 
   end 
 end 
 ~~~ 

 This is a fairly common way of dealing with exceptions where some condition above and beyond the exception's type determines whether the exception should be rescued. It's verbose, though, and it's not obvious at first glance exactly what conditions are being rescued, especially if "...handle error..." is more than a few lines long. I propose that the following be allowed: 

 ~~~ruby ~~~ 
 begin 
   ... 
 rescue SomeError => e if e.error_code == 1 
   ...handle error... 
 end 
 ~~~ 

 "unless" would, of course, be allowed as well: 

 ~~~ruby ~~~ 
 begin 
   ... 
 rescue SomeError => e unless e.error_code == 2 
   ...handle error... 
 end 
 ~~~ 

 A rescue statement whose boolean condition failed would be treated the same as if the exception being raised didn't match the exception being rescued, and move on to the next rescue statement: 

 ~~~ruby ~~~ 
 begin 
   ... 
 rescue SomeError => e if e.error_code == 1 
   ...handle error code 1... 
 rescue SomeError => e if e.error_code == 2 
   ...handle error code 2... 
 end 
 ~~~ 

 And finally, catch-all rescue statements would be allowed as well: 

 ~~~ruby ~~~ 
 begin 
   ... 
 rescue => e if e.message == "some error" 
   ...handle error... 
 end 
 ~~~ 

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