Implement the pwd builtin (#111)

With spec tests.

core/builtin.py

@@ -83,6 +83,7 @@
    "pushd": builtin_e.PUSHD,
    "popd": builtin_e.POPD,
    "dirs": builtin_e.DIRS,
    "pwd": builtin_e.PWD,

    "source": builtin_e.SOURCE,  # note that . alias is special

@@ -636,6 +637,25 @@ def Dirs(argv, home_dir, dir_stack):
  return 0


PWD_SPEC = _Register('pwd')
PWD_SPEC.ShortFlag('-L')
PWD_SPEC.ShortFlag('-P')


def Pwd(argv, mem):
  arg, i = PWD_SPEC.Parse(argv)

  pwd = mem.GetVar('PWD').s

  # `-L` is the default behavior; no need to check it
  # TODO: ensure that if multiple flags are provided, the *last* one overrides
  # the others
  if arg.P:
    pwd = os.path.realpath(pwd)
  print(pwd)
  return 0


EXPORT_SPEC = _Register('export')
EXPORT_SPEC.ShortFlag('-n')

core/cmd_exec.py

@@ -119,7 +119,7 @@ def __init__(self, mem, fd_state, status_lines, funcs, completion,
    """
    self.mem = mem
    self.fd_state = fd_state
    self.status_lines = status_lines  
    self.status_lines = status_lines
    # function space is different than var space.  Not hierarchical.
    self.funcs = funcs
    self.completion = completion
@@ -317,6 +317,9 @@ def _RunBuiltin(self, builtin_id, argv):
    elif builtin_id == builtin_e.DIRS:
      status = builtin.Dirs(argv, self.mem.GetVar('HOME'), self.dir_stack)

    elif builtin_id == builtin_e.PWD:
      status = builtin.Pwd(argv, self.mem)

    elif builtin_id in (builtin_e.SOURCE, builtin_e.DOT):
      status = self._Source(argv)

@@ -396,7 +399,7 @@ def _CheckStatus(self, status, node, argv0=None):
      elif node.tag == command_e.Assignment:
        span_id = self._SpanIdForAssignment(node)
        raise util.ErrExitFailure(
            '[%d] assignment exited with status %d', os.getpid(), 
            '[%d] assignment exited with status %d', os.getpid(),
            status, span_id=span_id, status=status)

      else:
@@ -863,7 +866,7 @@ def _Dispatch(self, node, fork_external):
          self.loop_level == 0):
        ok = False
        msg = 'Invalid control flow at top level'
      

      if ok:
        raise _ControlFlow(tok, arg)

@@ -1129,7 +1132,7 @@ def _Execute(self, node, fork_external=True):
    check_errexit = True

    if redirects is None:  # evaluation error
      status = 1  
      status = 1

    elif redirects:
      if self.fd_state.Push(redirects, self.waiter):
@@ -1411,7 +1414,7 @@ def RunFunc(self, func_node, argv):

class Tracer(object):
  """A tracer for this process.
  

  TODO: Connect it somehow to tracers for other processes.  So you can make an
  HTML report offline.

@@ -1421,7 +1424,7 @@ class Tracer(object):
    - argv and span ID of the SimpleCommand that corresponds to that
    - then print line number using arena
    - set -x doesn't print line numbers!  OH but you can do that with
      PS4=$LINENO 
      PS4=$LINENO
  """
  def __init__(self, exec_opts, mem, word_ev):
    """

core/runtime.asdl

@@ -67,6 +67,7 @@ module runtime
  | TEST | BRACKET | GETOPTS
  | COMMAND | TYPE | HELP
  | DECLARE | TYPESET
  | PWD

  -- word_eval.py: SliceParts is for ${a-} and ${a+}, Error is for ${a?}, and
  -- SliceAndAssign is for ${a=}.

spec/builtins.test.sh

@@ -28,6 +28,21 @@ echo "old: $OLDPWD"
cd -
# stdout-json: "old: /\n/\n"

### pwd
cd /
pwd
# stdout: /

### pwd -P
mkdir -p $TMP/symtarg
ln -s $TMP/symtarg $TMP/symlink
cd $TMP/symlink
basename $(pwd -P)
cd $TMP
rmdir $TMP/symtarg
rm $TMP/symlink
# stdout: symtarg

### cd with no arguments
HOME=$TMP/home
mkdir -p $HOME