Fix errexit with loops and { }.

Invert the approach to errexit so it's more reliable.

Only primitives like SimpleCommand, Assignment, DParen, DBracket, etc.
get checked.

Compound commands like loops, if/case, brace group, etc. don't get
checked.

core/cmd_exec.py

@@ -572,9 +572,10 @@ def _RunJobInBackground(self, node):

  def _Dispatch(self, node, fork_external):
    argv0 = None  # for error message
    check_errexit = True  # for errexit
    check_errexit = False  # for errexit

    if node.tag == command_e.SimpleCommand:
      check_errexit = True
      # PROBLEM: We want to log argv in 'xtrace' mode, but we may have already
      # redirected here, which screws up loggnig.  For example, 'echo hi
      # >/dev/null 2>&1'.  We want to evaluate argv and log it BEFORE applying
@@ -608,14 +609,14 @@ def _Dispatch(self, node, fork_external):
        pass

    elif node.tag == command_e.Sentence:
      # Don't check_errexit since this isn't a real node!
      if node.terminator.id == Id.Op_Semi:
        # Don't check_errexit since this isn't a real node!
        check_errexit = False
        status = self._Execute(node.child)
      else:
        status = self._RunJobInBackground(node.child)

    elif node.tag == command_e.Pipeline:
      check_errexit = True
      if node.stderr_indices:
        raise NotImplementedError('|&')

@@ -633,19 +634,23 @@ def _Dispatch(self, node, fork_external):
        status = self._RunPipeline(node)

    elif node.tag == command_e.Subshell:
      check_errexit = True
      # This makes sure we don't waste a process if we'd launch one anyway.
      p = self._MakeProcess(node.child)
      status = p.Run(self.waiter)

    elif node.tag == command_e.DBracket:
      check_errexit = True
      result = self.bool_ev.Eval(node.expr)
      status = 0 if result else 1

    elif node.tag == command_e.DParen:
      check_errexit = True
      i = self.arith_ev.Eval(node.child)
      status = 0 if i != 0 else 1

    elif node.tag == command_e.Assignment:
      check_errexit = True
      pairs = []
      if node.keyword == Id.Assign_Local:
        lookup_mode = scope.LocalOnly
@@ -711,13 +716,12 @@ def _Dispatch(self, node, fork_external):
    # redirects.  We already took care of that above.
    elif node.tag in (command_e.CommandList, command_e.BraceGroup):
      status = self._ExecuteList(node.children)
      check_errexit = False

    elif node.tag == command_e.AndOr:
      # TODO: We have to fix && || precedence.  See case #13 in
      # dbracket.test.sh.

      check_errexit = False  # only check last condition

      #print(node.children)
      left, right = node.children

@@ -731,11 +735,11 @@ def _Dispatch(self, node, fork_external):
      if node.op_id == Id.Op_DPipe:
        if status != 0:
          status = self._Execute(right)
          check_errexit = True  # status from last clause
          check_errexit = True  # only check last condition
      elif node.op_id == Id.Op_DAmp:
        if status == 0:
          status = self._Execute(right)
          check_errexit = True  # status from last clause
          check_errexit = True  # only check last condition
      else:
        raise AssertionError

@@ -802,6 +806,7 @@ def _Dispatch(self, node, fork_external):

    elif node.tag == command_e.DoGroup:
      status = self._ExecuteList(node.children)
      check_errexit = False  # not real statements

    elif node.tag == command_e.FuncDef:
      # NOTE: Would it make sense to evaluate the redirects BEFORE entering?
@@ -858,6 +863,7 @@ def _Dispatch(self, node, fork_external):
      start_t = time.time()  # calls gettimeofday() under the hood
      start_u = resource.getrusage(resource.RUSAGE_SELF)
      status = self._Execute(node.pipeline)

      end_t = time.time()
      end_u = resource.getrusage(resource.RUSAGE_SELF)

spec/sh-options.test.sh

@@ -218,6 +218,26 @@ echo status=$?
# stdout-json: ""
# status: 1

### errexit and loop
set -o errexit
for x in 1 2 3; do
  test $x = 2 && echo "hi $x"
done
# stdout: hi 2
# status: 1

### errexit and brace group { }
set -o errexit
{ test no = yes && echo hi; }
echo status=$?
# stdout: status=1

### errexit and time { }
set -o errexit
time false
echo status=$?
# status: 1

### errexit with !
set -o errexit
echo one