D9287: worker: raise exception instead of calling sys.exit() with child's code

[martinvonz (Martin von Zweigbergk)]

martinvonz created this revision.
Herald added a reviewer: hg-reviewers.
Herald added a subscriber: mercurial-patches.

REVISION SUMMARY
  When a worker process returns an error code, we would call
  `sys.exit()` with that exit code on the main process. The `SystemExit`
  exception would then get caught in `scmutil.callcatch()`, which would
  return that error code. The comment there says "Commands shouldn't
  sys.exit directly", which I agree with. This patch changes it so we
  raise a specific exception when a worker fails so we can catch
  instead. I think that means that `SystemExit` is now always an
  internal error.
  
  (I had earlier thought that this call to `sys.exit()` was from within
  the child process until Matt Harbison made me look again, so thanks
  for that!)

REPOSITORY
  rHG Mercurial

BRANCH
  default

REVISION DETAIL
  https://phab.mercurial-scm.org/D9287

AFFECTED FILES
  mercurial/error.py
  mercurial/scmutil.py
  mercurial/worker.py
  tests/test-worker.t

CHANGE DETAILS

diff --git a/tests/test-worker.t b/tests/test-worker.t
--- a/tests/test-worker.t
+++ b/tests/test-worker.t
@@ -85,11 +85,12 @@
   [255]
 
   $ hg --config "extensions.t=$abspath" --config 'worker.numcpus=8' \
-  > test 100000.0 abort --traceback 2>&1 | egrep '(SystemExit|Abort)'
+  > test 100000.0 abort --traceback 2>&1 | egrep '(WorkerError|Abort)'
       raise error.Abort(b'known exception')
   mercurial.error.Abort: known exception (py3 !)
   Abort: known exception (no-py3 !)
-  SystemExit: 255
+      raise error.WorkerError(status)
+  mercurial.error.WorkerError: 255
 
 Traceback must be printed for unknown exceptions
 
diff --git a/mercurial/worker.py b/mercurial/worker.py
--- a/mercurial/worker.py
+++ b/mercurial/worker.py
@@ -300,7 +300,7 @@
     if status:
         if status < 0:
             os.kill(os.getpid(), -status)
-        sys.exit(status)
+        raise error.WorkerError(status)
     if hasretval:
         yield True, retval
 
diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -219,6 +219,9 @@
         ui.error(_(b"abort: %s\n") % inst.message)
         if inst.hint:
             ui.error(_(b"(%s)\n") % inst.hint)
+    except error.WorkerError as inst:
+        # Don't print a message -- the worker already should have
+        return inst.status_code
     except ImportError as inst:
         ui.error(_(b"abort: %s!\n") % stringutil.forcebytestr(inst))
         m = stringutil.forcebytestr(inst).split()[-1]
diff --git a/mercurial/error.py b/mercurial/error.py
--- a/mercurial/error.py
+++ b/mercurial/error.py
@@ -130,6 +130,13 @@
     __bytes__ = _tobytes
 
 
+class WorkerError(Exception):
+    """Exception raised when a worker process dies."""
+
+    def __init__(self, status_code):
+        self.status_code = status_code
+
+
 class InterventionRequired(Hint, Exception):
     """Exception raised when a command requires human intervention."""
 



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