Add a "dump-json" generator that dumps the dependency graph.

pylib/gyp/generator/dump-json.py

Index: pylib/gyp/generator/dump-json.py
diff --git a/pylib/gyp/generator/dump-json.py b/pylib/gyp/generator/dump-json.py
new file mode 100644
index 0000000000000000000000000000000000000000..f017db506f514cdfe25cc3a3dcf1ae3fa339258a
--- /dev/null
+++ b/pylib/gyp/generator/dump-json.py
@@ -0,0 +1,56 @@
+#!/usr/bin/python
+
+# Copyright (c) 2011 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.
+
+import collections
+import gyp
+import gyp.common
+import json
+
+generator_wants_flattened_static_libraries = False
+
+generator_default_variables = {
+  'OS': 'linux',
+}
+for dirname in ['INTERMEDIATE_DIR', 'SHARED_INTERMEDIATE_DIR', 'PRODUCT_DIR',
+                'LIB_DIR', 'SHARED_LIB_DIR']:
+  # Some gyp steps fail if these are empty(!).
+  generator_default_variables[dirname] = 'dir'
+for unused in ['RULE_INPUT_PATH', 'RULE_INPUT_ROOT', 'RULE_INPUT_NAME',
+               'RULE_INPUT_EXT',
+               'EXECUTABLE_PREFIX', 'EXECUTABLE_SUFFIX',
+               'STATIC_LIB_PREFIX', 'STATIC_LIB_SUFFIX',
+               'SHARED_LIB_PREFIX', 'SHARED_LIB_SUFFIX',
+               'LINKER_SUPPORTS_ICF']:
+  generator_default_variables[unused] = ''
+
+
+def CalculateVariables(default_variables, params):
+  generator_flags = params.get('generator_flags', {})
+  default_variables['OS'] = generator_flags.get('os', 'linux')
+
+
+def GenerateOutput(target_list, target_dicts, data, params):
+  # Map of target -> list of targets it depends on.
+  edges = {}
+
+  # Queue of targets we've yet to visit.

[Mark Mentovai, 2011/05/24 21:46:15]

You know how I feel about “we” in comments.

+  targets_to_visit = target_list[:]
+
+  while len(targets_to_visit) > 0:
+    target = targets_to_visit.pop()
+    if target in edges:
+      continue
+    edges[target] = []
+
+    for dep in target_dicts[target].get('dependencies', []):
+      edges[target].append(dep)
+      targets_to_visit.append(dep)
+
+  filename = 'dump.json'
+  f = open(filename, 'w')
+  json.dump(edges, f)
+  f.close()
+  print 'Wrote json to %s.' % filename