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 the exceptions that happen in the thread being waited on.

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.

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

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):