More cleanups to word_eval.

- Remove CompoundPartValue and UndefPartValue variants.
- Get rid of unused function
- Make method public

core/cmd_exec_test.py

@@ -85,12 +85,12 @@ def testVarOps(self):
    ev = InitEvaluator()  # initializes x=xxx and y=yyy
    unset_sub = ast.BracedVarSub(ast.token(Id.VSub_Name, 'unset'))
    part_vals = []
    ev.part_ev._EvalWordPart(unset_sub, part_vals)
    ev.part_ev.EvalWordPart(unset_sub, part_vals)
    print(part_vals)

    set_sub = ast.BracedVarSub(ast.token(Id.VSub_Name, 'x'))
    part_vals = []
    ev.part_ev._EvalWordPart(set_sub, part_vals)
    ev.part_ev.EvalWordPart(set_sub, part_vals)
    print(part_vals)

    # Now add some ops
@@ -101,11 +101,11 @@ def testVarOps(self):
    set_sub.suffix_op = test_op

    part_vals = []
    ev.part_ev._EvalWordPart(unset_sub, part_vals)
    ev.part_ev.EvalWordPart(unset_sub, part_vals)
    print(part_vals)

    part_vals = []
    ev.part_ev._EvalWordPart(set_sub, part_vals)
    ev.part_ev.EvalWordPart(set_sub, part_vals)
    print(part_vals)

core/runtime.asdl

@@ -8,19 +8,15 @@

module runtime
{
  -- A static word_part from os.asdl is evaluated to a dynamic part_value.
  -- A static word_part from osh.asdl is evaluated to a dynamic part_value.
  part_value = 
    -- UndefPartValue is for internal processing only.
    UndefPartValue
    -- Substitutions get split/elided/globbed.  Unquoted literals also get
    -- globbed.
  | StringPartValue(string s, bool do_split_glob)
    -- Substitutions and unquoted literals get split/elided/globbed.
    StringPartValue(string s, bool do_split_glob)
    -- "$@" or "${a[@]}" -- never split or globbed since double quoted.
  | ArrayPartValue(string* strs)
  | CompoundPartValue(part_value* children)

  -- A static word from osh.asdl is evaluted to a dynamic value.  value
  -- instances are stored in memory.
  -- instances are stored in state.Mem().
  value =
    -- Undef isn't visible at the language level.  We model it as a value
    -- rather than an error code because it's manipulated with ${a:-default}

core/word_eval.py

@@ -27,18 +27,20 @@


def _ValueToPartValue(val, quoted):
  """Helper for VarSub evaluation."""
  """Helper for VarSub evaluation.

  Called by _EvalBracedVarSub and _EvalWordPart for SimpleVarSub.
  """
  assert isinstance(val, runtime.value), val
  if val.tag == value_e.Undef:
    return runtime.UndefPartValue()

  elif val.tag == value_e.Str:
  if val.tag == value_e.Str:
    return runtime.StringPartValue(val.s, not quoted)

  elif val.tag == value_e.StrArray:
    return runtime.ArrayPartValue(val.strs)

  else:
    # Undef should be caught by _EmptyStrOrError().
    raise AssertionError


@@ -484,7 +486,7 @@ def _EvalDoubleQuotedPart(self, part, part_vals):
      return

    for p in part.parts:
      self._EvalWordPart(p, part_vals, quoted=True)
      self.EvalWordPart(p, part_vals, quoted=True)

  def _DecayArray(self, val):
    sep = _GetJoinChar(self.mem)
@@ -711,10 +713,12 @@ def _EvalBracedVarSub(self, part, part_vals, quoted):
    # No prefix or suffix ops
    val = self._EmptyStrOrError(val)

    # For example, ${a} evaluates to value_t.Str(), but we want a
    # part_value.StringPartValue.
    part_val = _ValueToPartValue(val, quoted)
    part_vals.append(part_val)

  def _EvalWordPart(self, part, part_vals, quoted=False):
  def EvalWordPart(self, part, part_vals, quoted=False):
    """Evaluate a word part.

    Args:
@@ -798,14 +802,6 @@ def _EvalWordPart(self, part, part_vals, quoted=False):
      raise AssertionError(part.__class__.__name__)


def _FlattenPartValues(part_vals, out):
  for pval in part_vals:
    if pval.tag == part_value_e.CompoundPartValue:
      _FlattenPartValues(pval.children, out)
    else:
      out.append(pval)


class _WordEvaluator:
  """Abstract base class for word evaluators.

@@ -834,7 +830,7 @@ def _EvalWordToParts(self, word, quoted, part_vals):
        "Expected CompoundWord, got %s" % word

    for p in word.parts:
      v = self.part_ev._EvalWordPart(p, part_vals, quoted=quoted)
      v = self.part_ev.EvalWordPart(p, part_vals, quoted=quoted)

  def EvalWordToString(self, word, do_fnmatch=False, decay=False):
    """
@@ -850,7 +846,7 @@ def EvalWordToString(self, word, do_fnmatch=False, decay=False):
    """
    part_vals = []
    for part in word.parts:
      self.part_ev._EvalWordPart(part, part_vals, quoted=False)
      self.part_ev.EvalWordPart(part, part_vals, quoted=False)

    strs = []
    for part_val in part_vals: