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Bug #15644

Updated by kke (Kimmo Lehto) over 1 year ago

Using ThreadsWait with Thread.report_on_exception is confusing. 

 ThreadsWait spawns a new thread for waiting on a thread: 

 ``` 
   # thwait.rb:87 
   def join_nowait(*threads) 
     threads.flatten! 
     @threads.concat threads 
     for th in threads 
       Thread.start(th) do |t| 
         begin 
           t.join 
         ensure 
           @wait_queue.push t 
         end 
       end 
     end 
   end 
 ``` 

 The `t.join` in `ThreadsWait` will re-raise As `thread.join` raises the exceptions that happen in exception from the thread, it will trigger a thread being waited on. exception report. 

 If the thread being waited on was using `report_on_exception = false`, the wait thread will report the exception and the `report_on_exception = false` effectively did nothing, as you still got an exception report.  

 anyway. 

 If the thread was using `report_on_exception = true`, both threads will report the exception, so you get it twice. exception. 

 I think this could be fixed by always setting `report_on_exception = false` for the wait thread. 

 # Example 1 

 ``` 
 require 'thwait' 

 thread = Thread.new do 
   Thread.current.report_on_exception = false 
   sleep 1 
   raise "Foo" 
 end 

 ThreadsWait.all_waits(thread) do |terminated_thread| 
   puts "Thread #{terminated_thread} terminated" 
 end 
 ``` 

 ## Expected result 

 No exception reports 

 ## Actual result 

 The wait thread will report the exception: 

 ``` 
 #<Thread:0x00007fa57d092d68@/Users/user/.rbenv/versions/2.6.1/lib/ruby/2.6.0/thwait.rb:91 run> terminated with exception (report_on_exception is true): 
 ``` 


 # Example 2 

 ``` 
 require 'thwait' 

 thread = Thread.new do 
   sleep 1 
   raise "Foo" 
 end 

 ThreadsWait.all_waits(thread) do |terminated_thread| 
   puts "Thread #{terminated_thread} terminated" 
 end 
 ``` 

 ## Expected result 

 One exception report 

 ## Actual result 

 Two exception reports: 

 ``` 
 #<Thread:0x00007f9f83053320@test.rb:3 run> terminated with exception (report_on_exception is true): 
 #<Thread:0x00007f9f830530a0@/Users/user/.rbenv/versions/2.6.1/lib/ruby/2.6.0/thwait.rb:91 run> terminated with exception (report_on_exception is true): 
 Traceback (most recent call last): 
 ``` 

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