(env)
Takes a dict |env| whose values are strings that can refer to other keys,
  for example env['foo'] = '$(bar) and $(baz)'. Returns a list L of all keys of
  env such that key2 is after key1 in L if env[key2] refers to env[key1].

  Throws an Exception in case of dependency cycles.
Takes a dict |env| whose values are strings that can refer to other keys,
  for example env['foo'] = '$(bar) and $(baz)'. Returns a list L of all keys of
  env such that key2 is after key1 in L if env[key2] refers to env[key1].
Takes a dict |env| whose values are strings that can refer to other keys for example env [ foo ] = $ ( bar ) and $ ( baz ) . Returns a list L of all keys of env such that key2 is after key1 in L if env [ key2 ] refers to env [ key1 ] .
def _TopologicallySortedEnvVarKeys(env):
  """Takes a dict |env| whose values are strings that can refer to other keys,
  for example env['foo'] = '$(bar) and $(baz)'. Returns a list L of all keys of
  env such that key2 is after key1 in L if env[key2] refers to env[key1].

  Throws an Exception in case of dependency cycles.
  """
  # Since environment variables can refer to other variables, the evaluation
  # order is important. Below is the logic to compute the dependency graph
  # and sort it.
  regex = re.compile(r'\$\{([a-zA-Z0-9\-_]+)\}')
  def GetEdges(node):
    # Use a definition of edges such that user_of_variable -> used_varible.
    # This happens to be easier in this case, since a variable's
    # definition contains all variables it references in a single string.
    # We can then reverse the result of the topological sort at the end.
    # Since: reverse(topsort(DAG)) = topsort(reverse_edges(DAG))
    matches = set([v for v in regex.findall(env[node]) if v in env])
    for dependee in matches:
      assert '${' not in dependee, 'Nested variables not supported: ' + dependee
    return matches

  try:
    # Topologically sort, and then reverse, because we used an edge definition
    # that's inverted from the expected result of this function (see comment
    # above).
    order = gyp.common.TopologicallySorted(env.keys(), GetEdges)
    order.reverse()
    return order
  except gyp.common.CycleError, e:
    raise GypError(
        'Xcode environment variables are cyclically dependent: ' + str(e.nodes))
def _TopologicallySortedEnvVarKeys ( env ) : # Since environment variables can refer to other variables, the evaluation # order is important. Below is the logic to compute the dependency graph # and sort it. regex = re . compile ( r'\$\{([a-zA-Z0-9\-_]+)\}' ) def GetEdges ( node ) : # Use a definition of edges such that user_of_variable -> used_varible. # This happens to be easier in this case, since a variable's # definition contains all variables it references in a single string. # We can then reverse the result of the topological sort at the end. # Since: reverse(topsort(DAG)) = topsort(reverse_edges(DAG)) matches = set ( [ v for v in regex . findall ( env [ node ] ) if v in env ] ) for dependee in matches : assert '${' not in dependee , 'Nested variables not supported: ' + dependee return matches try : # Topologically sort, and then reverse, because we used an edge definition # that's inverted from the expected result of this function (see comment # above). order = gyp . common . TopologicallySorted ( env . keys ( ) , GetEdges ) order . reverse ( ) return order except gyp . common . CycleError , e : raise GypError ( 'Xcode environment variables are cyclically dependent: ' + str ( e . nodes ) )