GTTF: Print much better error message for dependency cycles.

pylib/gyp/input.py

 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from compiler.ast import Const
 from compiler.ast import Dict
 from compiler.ast import Discard
 from compiler.ast import List
 from compiler.ast import Module
 from compiler.ast import Node
@@ skipping 1425 matching lines @@
   """
 
   class CircularException(GypError):
     pass
 
   def __init__(self, ref):
     self.ref = ref
     self.dependencies = []
     self.dependents = []
 
+  def __repr__(self):
+    return '<DependencyGraphNode: %r>' % self.ref
+
   def FlattenToList(self):
     # flat_list is the sorted list of dependencies - actually, the list items
     # are the "ref" attributes of DependencyGraphNodes.  Every target will
     # appear in flat_list after all of its dependencies, and before all of its
     # dependents.
     flat_list = []
 
     # in_degree_zeros is the list of DependencyGraphNodes that have no
     # dependencies not in flat_list.  Initially, it is a copy of the children
     # of this node, because when the graph was built, nodes with no
@@ skipping 22 matching lines @@
             break
 
         if is_in_degree_zero:
           # All of the dependent's dependencies are already in flat_list.  Add
           # it to in_degree_zeros where it will be processed in a future
           # iteration of the outer loop.
           in_degree_zeros.add(node_dependent)
 
     return flat_list
 
+  def FindCycles(self, path=None):
+    """
+    Returns a list of cycles in the graph, where each cycle is its own list.
+    """
+    if path is None:
+      path = [self]
+
+    results = []
+    for node in self.dependents:
+      if node in path:
+        cycle = [node]
+        for part in path:
+          cycle.append(part)
+          if part == node:
+            break
+        results.append(tuple(cycle))
+      else:
+        results.extend(node.FindCycles([node] + path))
+
+    return list(set(results))
+
   def DirectDependencies(self, dependencies=None):
     """Returns a list of just direct dependencies."""
     if dependencies == None:
       dependencies = []
 
     for dependency in self.dependencies:
       # Check for None, corresponding to the root node.
       if dependency.ref != None and dependency.ref not in dependencies:
         dependencies.append(dependency.ref)
 
@@ skipping 212 matching lines @@
 
   flat_list = root_node.FlattenToList()
 
   # If there's anything left unvisited, there must be a circular dependency
   # (cycle).
   if len(flat_list) != len(dependency_nodes):
     bad_files = []
     for file in dependency_nodes.iterkeys():
       if not file in flat_list:
         bad_files.append(file)
+    common_path_prefix = os.path.commonprefix(dependency_nodes)
+    cycles = []
+    for cycle in root_node.FindCycles():
+      simplified_paths = []
+      for node in cycle:
+        assert(node.ref.startswith(common_path_prefix))
+        simplified_paths.append(node.ref[len(common_path_prefix):])
+      cycles.append('Cycle: %s' % ' -> '.join(simplified_paths))
     raise DependencyGraphNode.CircularException, \
-        'Some files not reachable, cycle in .gyp file dependency graph ' + \
-        'detected involving some or all of: ' + \
-        ' '.join(bad_files)
+        'Cycles in .gyp file dependency graph detected:\n' + '\n'.join(cycles)
 
 
 def DoDependentSettings(key, flat_list, targets, dependency_nodes):
   # key should be one of all_dependent_settings, direct_dependent_settings,
   # or link_settings.
 
   for target in flat_list:
     target_dict = targets[target]
     build_file = gyp.common.BuildFile(target)
 
@@ skipping 940 matching lines @@
     ValidateRunAsInTarget(target, target_dict, build_file)
     ValidateActionsInTarget(target, target_dict, build_file)
 
   # Generators might not expect ints.  Turn them into strs.
   TurnIntIntoStrInDict(data)
 
   # TODO(mark): Return |data| for now because the generator needs a list of
   # build files that came in.  In the future, maybe it should just accept
   # a list, and not the whole data dict.
   return [flat_list, targets, data]