[errors] Tweak the appearance of fatal error messages from 'errexit'.

Addresses #168.

osh/cmd_exec.py

@@ -404,25 +404,27 @@ def _PushErrExit(self):
   def _PopErrExit(self):
     self.exec_opts.errexit.Pop()
 
-  def _CheckStatus(self, status, node, argv0=None):
+  def _CheckStatus(self, status, node):
     """ErrExitFailure with location info attached."""
     if self.exec_opts.ErrExit() and status != 0:
-      # Add context based on node type
+      # TODO: only print location info for external commands?  Any errors
+      # generated by builtins or the shell itself will already have location
+      # info printed (e.g. command not found)
+
       if node.tag == command_e.SimpleCommand:
-        argv0 = argv0 or '<unknown>'
         raise util.ErrExitFailure(
-            '[%d] %r command exited with status %d', posix.getpid(), argv0,
-            status, word=node.words[0], status=status)
+            'Exiting with status %d (command, PID %d)', status, posix.getpid(),
+            word=node.words[0], status=status)
       elif node.tag == command_e.Assignment:
         span_id = self._SpanIdForAssignment(node)
         raise util.ErrExitFailure(
-            '[%d] assignment exited with status %d', posix.getpid(),
-            status, span_id=span_id, status=status)
-
+            'Exiting with status %d (assignment, PID %d)', status, posix.getpid(),
+            span_id=span_id, status=status)
       else:
+        # No location info
         raise util.ErrExitFailure(
-            '[%d] %r exited with status %d', posix.getpid(),
-            node.__class__.__name__, status, status=status)
+            'Exiting with status %d (in PID %d)', status, posix.getpid(),
+            status=status)
 
   def _EvalLhs(self, node, spid, lookup_mode):
     """lhs_expr -> lvalue."""

test/runtime-errors.sh

@@ -67,6 +67,13 @@ failed_command() {
   echo 'SHOULD NOT GET HERE'
 }
 
+errexit() {
+  set -o errexit
+  rm nonexistent/file
+
+  echo 'SHOULD NOT GET HERE'
+}
+
 pipefail() {
   false | wc -l
 
@@ -394,7 +401,7 @@ all() {
 
   for t in \
     no_such_command no_such_command_commandsub no_such_command_heredoc \
-    failed_command \
+    failed_command errexit \
     pipefail pipefail_group pipefail_subshell pipefail_func pipefail_while \
     pipefail_multiple core_process \
     nonexistent nounset bad_var_ref \