Correct the order in which OutputDirectory and IntermediateDirectory are defined.

pylib/gyp/xcode_emulation.py

Index: pylib/gyp/xcode_emulation.py
===================================================================
--- pylib/gyp/xcode_emulation.py	(revision 1364)
+++ pylib/gyp/xcode_emulation.py	(working copy)
@@ -968,7 +968,7 @@
   expansions dict. If the variable expands to something that references
   another variable, this variable is expanded as well if it's in env --
   until no variables present in env are left."""
-  for k in reversed(TopologicallySortedEnvVarKeys(expansions)):
+  for k in TopologicallySortedEnvVarKeys(expansions):
     string = string.replace('${' + k + '}', expansions[k])
     string = string.replace('$(' + k + ')', expansions[k])
     string = string.replace('$' + k, expansions[k])
@@ -978,7 +978,7 @@
 def TopologicallySortedEnvVarKeys(env):
   """Takes a dict |env| whose values are strings that can refer to other keys,
   for example env['foo'] = '$(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].
+  env such that key1 is after key2 in L if env[key2] refers to env[key1].
 
   Throws an Exception in case of dependency cycles.
   """
@@ -986,62 +986,20 @@
   # order is important. Below is the logic to compute the dependency graph
   # and sort it.
   regex = re.compile(r'\$\{([a-zA-Z0-9\-_]+)\}')
-
-  # First sort the list of keys.
-  key_list = sorted(env.keys())
-
-  # Phase 1: Create a set of edges of (DEPENDEE, DEPENDER) where in the graph,
-  # DEPENDEE -> DEPENDER. Also create sets of dependers and dependees.
-  edges = set()
-  dependees = set()
-  dependers = set()
-  for k in key_list:
-    matches = regex.findall(env[k])
-    if not len(matches):
-      continue
-
-    depends_on_other_var = False
+  def GetEdges(node):

[Nico, 2012/05/11 14:53:44]

This function is the wrong way round. We want an edge from a to b if a is needed
to define b (i.e. "b = $a"), not when a is defined in terms of b (i.e. "a =
$b"). This function builds the reverse of the DAG that was previously used.

I have convinced myself that reverse(toposort(graph)) is the same as
toposort(revert_dag(graph)), so be reverting the result of gyp.common.TopoSort
you will get the correct result. But I think that's not obvious, so either:

1.) Change GetEdges() to build the graph the right way round

2.) Put the reverse() call into this function instead of at the various call
sites, and add a comment that points out that the the reverse of the topological
sorting on a reversed DAG is equivalent to a topological sorting on the original
DAG

[bradn, 2012/05/11 18:57:23]

Done.

+    # Get all variable references for variable defined in env.
+    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
-      if dependee in env:
-        edges.add((dependee, k))
-        dependees.add(dependee)
-        depends_on_other_var = True
-    if depends_on_other_var:
-      dependers.add(k)
+    return matches
 
-  # Phase 2: Create a list of graph nodes with no incoming edges.
-  sorted_nodes = []
-  edgeless_nodes = dependees - dependers
+  try:
+    return gyp.common.TopologicallySorted(env.keys(), GetEdges)
+  except CycleError, e:
+    raise Exception(
+        'Xcode environment variables are cyclically dependent: ' + str(e.nodes))
 
-  # Phase 3: Perform Kahn topological sort.
-  while len(edgeless_nodes):
-    # Find a node with no incoming edges, add it to the sorted list, and
-    # remove it from the list of nodes that aren't part of the graph.
-    node = edgeless_nodes.pop()
-    sorted_nodes.append(node)
-    key_list.remove(node)
 
-    # Find all the edges between |node| and other nodes.
-    edges_to_node = [e for e in edges if e[0] == node]
-    for edge in edges_to_node:
-      edges.remove(edge)
-      # If the node connected to |node| by |edge| has no other incoming edges,
-      # add it to |edgeless_nodes|.
-      if not len([e for e in edges if e[1] == edge[1]]):
-        edgeless_nodes.add(edge[1])
-
-  # Any remaining edges indicate a cycle.
-  if len(edges):
-    raise Exception('Xcode environment variables are cyclically dependent: ' +
-        str(edges))
-
-  # Append the "nodes" not in the graph to those that were just sorted.
-  sorted_nodes.extend(key_list)
-
-  return sorted_nodes
-
-
 def GetSpecPostbuildCommands(spec, quiet=False):
   """Returns the list of postbuilds explicitly defined on |spec|, in a form
   executable by a shell."""