Overwrite sys.excepthook to handle exceptions in the main application.tristan/except-hook-no-test

This uses the existing messaging system to report errors in the main
application as a BUG type. It requires the use of a global_app variable
which isn't ideal; this may be replaced in future. This partially addresses
issue #197.

Theoretically, an exception could occur before Scheduler.loop is set up,
hence the check for it when terminating all jobs.

NOTE: This was originally submitted by Jim MacArthur, and manually
      reapplied after some refactoring took place.

1 files changed, 21 insertions, 0 deletions

diff --git a/buildstream/_frontend/app.py b/buildstream/_frontend/app.py
index 1ad1f059e..c32f8c90b 100644
--- a/buildstream/_frontend/app.py
+++ b/buildstream/_frontend/app.py
@@ -22,6 +22,7 @@ import os
 import sys
 import shutil
 import resource
+import traceback
 import datetime
 from textwrap import TextWrapper
 from contextlib import contextmanager
@@ -189,6 +190,10 @@ class App():
         # Propagate pipeline feedback to the user
         self.context.set_message_handler(self._message_handler)
 
+        # Now that we have a logger and message handler,
+        # we can override the global exception hook.
+        sys.excepthook = self._global_exception_handler
+
         try:
             self.project = Project(directory, self.context, cli_options=self._main_options['option'])
         except LoadError as e:
@@ -550,6 +555,22 @@ class App():
         self.context.message(
             Message(None, message_type, message, **args))
 
+    # Exception handler
+    #
+    def _global_exception_handler(self, etype, value, tb):
+
+        # Print the regular BUG message
+        formatted = "".join(traceback.format_exception(etype, value, tb))
+        self._message(MessageType.BUG, str(value),
+                      detail=formatted)
+
+        # If the scheduler has started, try to terminate all jobs gracefully,
+        # otherwise exit immediately.
+        if self.scheduler.loop:
+            self.scheduler.terminate_jobs()
+        else:
+            sys.exit(-1)
+
     #
     # Render the status area, conditional on some internal state
     #