nobs loses exit code when piping errors to PAGER

[Dan Bonachea]

Nobs is exiting with the a zero exit code on Linux (pcp-d) after generating an error that consumes more lines that fit on the terminal.

Example of correct behavior, for a synthetic error:

$ . sourceme
$ rm -Rf .nobs/ ; env PAGER=cat CXX=noexists nobs exe test/future.cpp ; echo $?                                              
noexists -std=c++11 -D_GNU_SOURCE=1 -I/home/pcp1/bonachea/UPC/upcxx/.nobs/art/9567f52ffd5df5bcd59711dba1d52b9d76423aa5 -MM -MT x /home/pcp1/bonachea/UPC/upcxx/test/future.cpp

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Uncaught exception

Traceback (most recent call last):
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/tool_main.py", line 87, in main
    printed.wait()
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/async.py", line 447, in wait
    return me.wait_futurized().value()
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/async.py", line 751, in fire
    arg = gen_throw(arg.exception, None, arg.traceback)
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/memodb.py", line 438, in memo_execute
    yield result
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/async.py", line 751, in fire
    arg = gen_throw(arg.exception, None, arg.traceback)
  File "/home/pcp1/bonachea/UPC/upcxx/nobsrule.py", line 536, in execute
    objs, libset = yield me.crawl()
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/async.py", line 751, in fire
    arg = gen_throw(arg.exception, None, arg.traceback)
  File "/home/pcp1/bonachea/UPC/upcxx/nobsrule.py", line 508, in crawl
    yield fresh_src(main_src)
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/async.py", line 601, in fire1
    proxied = lam(arg_result)
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/memodb.py", line 520, in result
    return resultoid()
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/async.py", line 751, in fire
    arg = gen_throw(arg.exception, None, arg.traceback)
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/memodb.py", line 438, in memo_execute
    yield result
  File "/home/pcp1/bonachea/UPC/upcxx/nobs/nobs/async.py", line 749, in fire
    arg = gen_send(arg.value())
  File "/home/pcp1/bonachea/UPC/upcxx/nobsrule.py", line 404, in execute
    mk = mk[mk.index(":")+1:]
ValueError: substring not found
1

However make no other change except shrinking the vertical size of your terminal window and when re-running the last lines instead become:

ValueError: substring not found
0

with the more common multi-page template errors, the exit code is almost always dropped.

This incorrect error code is also propagating to the result of the install script.

[Former user]

Easy fix, but I'm curious as to what in your workflow is sensitive to this? If paging is active (no redirection happening) then I'm assuming its the top-level user at the prompt who usually doesn't care about the previous commands exit status ($?).

[Former user]

Fixed issue 35: https://bitbucket.org/berkeleylab/upcxx/issues/35/nobs-loses-exit-code-when-piping-errors-to

→ <<cset f054d55027e5>>

[Dan Bonachea]

Thanks John.

The nightly CI sets PAGER=cat exactly because it is not an interactive user, but it does care about the exit code as one way to detect failures. Although it's also redirecting output to a file, so perhaps this bug was not relevant there.

The updates I made yesterday to the install script also use the exit code to print a final line of output after a nobs failure with instructions on submitting a bug report.