Dropping in software construction toolkit.

site_scons/site_tools/defer.py

Index: site_scons/site_tools/defer.py
===================================================================
--- site_scons/site_tools/defer.py	(revision 0)
+++ site_scons/site_tools/defer.py	(revision 0)
@@ -0,0 +1,178 @@
+#!/usr/bin/python2.4
+# Copyright 2008, Google Inc.
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Defer tool for SCons."""
+
+
+import os
+import sys
+import types
+
+
+__defer_groups = {}
+
+
+def _InitializeDefer(self):
+  """Re-initializes deferred function handling.
+
+  Args:
+    self: Parent environment
+  """
+  # Clear the list of deferred groups
+  __defer_groups.clear()
+
+
+def _ExecuteDefer(self):
+  """Executes deferred functions.
+
+  Args:
+    self: Parent environment
+  """
+  # Save directory, so SConscript functions can occur in the right subdirs
+  oldcwd = os.getcwd()
+
+  # Loop through deferred functions
+  while __defer_groups:
+    did_work = False
+    for name, group in __defer_groups.items():
+      if group.after.intersection(__defer_groups.keys()):
+        continue        # Still have dependencies
+      if group.func_env_cwd:
+        # Run all the functions in our named group
+        for func, env, cwd in group.func_env_cwd:
+          os.chdir(cwd)
+          func(env)
+      did_work = True
+      del __defer_groups[name]
+      break
+    if not did_work:
+      print 'Error in _ExecuteDefer: dependency cycle detected.'
+      for name, group in __defer_groups.items():
+        print '   %s after: %s' % (name, group.after)
+      # TODO(rspangler): should throw exception?
+      sys.exit(1)
+
+  # Restore directory
+  os.chdir(oldcwd)
+
+
+class DeferFunc(object):
+  """Named list of functions to be deferred."""
+
+  def __init__(self):
+    """Initialize deferred function object."""
+    object.__init__(self)
+    self.func_env_cwd = []
+    self.after = set()
+
+
+def Defer(self, *args, **kwargs):
+  """Adds a deferred function or modifies defer dependencies.
+
+  Args:
+    self: Environment in which Defer() was called
+    args: Positional arguments
+    kwargs: Named arguments
+
+  The deferred function will be passed the environment used to call Defer(),
+  and will be executed in the same working directory as the calling SConscript.
+
+  All deferred functions run after all SConscripts.  Additional dependencies
+  may be specified with the after= keyword.
+
+  Usage:
+
+    env.Defer(func)
+      # Defer func() until after all SConscripts
+
+    env.Defer(func, after=otherfunc)
+      # Defer func() until otherfunc() runs
+
+    env.Defer(func, 'bob')
+      # Defer func() until after SConscripts, put in group 'bob'
+
+    env.Defer(func2, after='bob')
+      # Defer func2() until after all funcs in 'bob' group have run
+
+    env.Defer(func3, 'sam')
+      # Defer func3() until after SConscripts, put in group 'sam'
+
+    env.Defer('bob', after='sam')
+      # Defer all functions in group 'bob' until after all functions in group
+      # 'sam' have run.
+
+    env.Defer(func4, after=['bob', 'sam'])
+      # Defer func4() until after all functions in groups 'bob' and 'sam' have
+      # run.
+  """
+  # Get name of group to defer and/or the a function
+  name = None
+  func = None
+  for a in args:
+    if isinstance(a, str):
+      name = a
+    elif isinstance(a, types.FunctionType):
+      func = a
+  if func and not name:
+    name = func.__name__
+
+  # Get list of names and/or functions this function should defer until after
+  after = []
+  for a in self.Flatten(kwargs.get('after')):
+    if isinstance(a, str):
+      after.append(a)
+    elif isinstance(a, types.FunctionType):
+      after.append(a.__name__)
+    elif a is not None:
+      # Deferring
+      # TODO(rspangler): should throw an exception
+      print ('Warning: Defer can only wait for functions or names; ignoring'
+             'after = ', a)
+
+  # Find the deferred function
+  if name not in __defer_groups:
+    __defer_groups[name] = DeferFunc()
+  group = __defer_groups[name]
+
+  # If we were given a function, also save environment and current directory
+  if func:
+    group.func_env_cwd.append((func, self, os.getcwd()))
+
+  # Add dependencies for the function
+  group.after.update(after)
+
+
+def generate(env):
+  # NOTE: SCons requires the use of this name, which fails gpylint.
+  """SCons entry point for this tool."""
+
+  env.AddMethod(_InitializeDefer)
+  env.AddMethod(_ExecuteDefer)
+  env.AddMethod(Defer)