Fix parsing of for (( )) loops.

We weren't properly accounting for spaces in the conditions.

This was caught by a 'bashdb' source file with an empty initial
condition.

Added tests.

osh/word_parse.py

@@ -846,33 +846,38 @@ def ReadDParen(self):

    return anode

  def _NextNonSpace(self):
    """Same logic as _ReadWord, but for ReadForExpresion."""
    while True:
      self._Next(lex_mode_e.ARITH)
      self._Peek()
      if self.token_kind not in (Kind.Ignored, Kind.WS):
        break

  def ReadForExpression(self):
    """Read ((i=0; i<5; ++i)) -- part of command context."""
    # No PushHint because we're in arith state.
    #self.lexer.PushHint(Id.Op_RParen, Id.Op_DRightParen)

    self._Next(lex_mode_e.ARITH)  # skip over ((
    self._NextNonSpace()  # skip over ((

    self._Peek()
    if self.token_type == Id.Arith_Semi:  # for (( ; i < 10; i++ ))
      init_node = None
    else:
      init_node = self._ReadArithExpr(do_next=False)
    self._Next(lex_mode_e.ARITH)
    self._NextNonSpace()

    self._Peek()
    if self.token_type == Id.Arith_Semi:  # for (( ; ; i++ ))
      cond_node = None
    else:
      cond_node = self._ReadArithExpr(do_next=False)
    self._Next(lex_mode_e.ARITH)
    self._NextNonSpace()

    self._Peek()
    if self.token_type == Id.Arith_RParen:  # for (( ; ; ))
      update_node = None
    else:
      update_node = self._ReadArithExpr(do_next=False)
    self._Next(lex_mode_e.ARITH)
    self._NextNonSpace()

    self._Peek()
    if self.token_type != Id.Arith_RParen:

spec/for-expr.test.sh

@@ -14,23 +14,22 @@ do
    break
  fi
  echo $a
done  # A construct borrowed from ksh93.
done
## status: 0
## STDOUT:
1
2
4
5
## N-I mksh status: 1
## N-I mksh stdout-json: ""
## END

#### For loop with and without semicolon
for ((a=1; a <= 3; a++)); do
  echo $a
done  # A construct borrowed from ksh93.
done
for ((a=1; a <= 3; a++)) do
  echo $a
done  # A construct borrowed from ksh93.
done
## status: 0
## STDOUT:
1
@@ -39,21 +38,46 @@ done  # A construct borrowed from ksh93.
1
2
3
## N-I mksh status: 1
## N-I mksh stdout-json: ""
## END

#### For loop with empty head
#### Empty init
i=1
for ((  ;i < 4;  i++ )); do
  echo $i
done
## status: 0
## STDOUT:
1
2
3
## END

#### Empty init and cond
i=1
for ((  ; ;  i++ )); do
  if test $i = 4; then
    break
  fi
  echo $i
done
## status: 0
## STDOUT:
1
2
3
## END

#### Infinite loop with ((;;))
a=1
for ((;;)); do
for ((  ;  ;  )); do
  if test $a = 4; then
    break
  fi
  echo $((a++))
done  # A construct borrowed from ksh93.
done
## status: 0
## STDOUT:
1
2
3
## N-I mksh status: 1
## N-I mksh stdout-json: ""
## END

test/spec.sh

@@ -591,7 +591,7 @@ let() {

for-expr() {
  sh-spec spec/for-expr.test.sh \
    $MKSH $BASH $OSH "$@"
    $BASH $ZSH $OSH "$@"
}

empty-bodies() {