Added an unmodified copy of SCons to third_party.

scons-2.0.1/engine/SCons/Action.py

+"""SCons.Action
+
+This encapsulates information about executing any sort of action that
+can build one or more target Nodes (typically files) from one or more
+source Nodes (also typically files) given a specific Environment.
+
+The base class here is ActionBase.  The base class supplies just a few
+OO utility methods and some generic methods for displaying information
+about an Action in response to the various commands that control printing.
+
+A second-level base class is _ActionAction.  This extends ActionBase
+by providing the methods that can be used to show and perform an
+action.  True Action objects will subclass _ActionAction; Action
+factory class objects will subclass ActionBase.
+
+The heavy lifting is handled by subclasses for the different types of
+actions we might execute:
+
+    CommandAction
+    CommandGeneratorAction
+    FunctionAction
+    ListAction
+
+The subclasses supply the following public interface methods used by
+other modules:
+
+    __call__()
+        THE public interface, "calling" an Action object executes the
+        command or Python function.  This also takes care of printing
+        a pre-substitution command for debugging purposes.
+
+    get_contents()
+        Fetches the "contents" of an Action for signature calculation
+        plus the varlist.  This is what gets MD5 checksummed to decide
+        if a target needs to be rebuilt because its action changed.
+
+    genstring()
+        Returns a string representation of the Action *without*
+        command substitution, but allows a CommandGeneratorAction to
+        generate the right action based on the specified target,
+        source and env.  This is used by the Signature subsystem
+        (through the Executor) to obtain an (imprecise) representation
+        of the Action operation for informative purposes.
+
+
+Subclasses also supply the following methods for internal use within
+this module:
+
+    __str__()
+        Returns a string approximation of the Action; no variable
+        substitution is performed.
+
+    execute()
+        The internal method that really, truly, actually handles the
+        execution of a command or Python function.  This is used so
+        that the __call__() methods can take care of displaying any
+        pre-substitution representations, and *then* execute an action
+        without worrying about the specific Actions involved.
+
+    get_presig()
+        Fetches the "contents" of a subclass for signature calculation.
+        The varlist is added to this to produce the Action's contents.
+
+    strfunction()
+        Returns a substituted string representation of the Action.
+        This is used by the _ActionAction.show() command to display the
+        command/function that will be executed to generate the target(s).
+
+There is a related independent ActionCaller class that looks like a
+regular Action, and which serves as a wrapper for arbitrary functions
+that we want to let the user specify the arguments to now, but actually
+execute later (when an out-of-date check determines that it's needed to
+be executed, for example).  Objects of this class are returned by an
+ActionFactory class that provides a __call__() method as a convenient
+way for wrapping up the functions.
+
+"""
+
+# Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 The SCons Foundation
+#
+# Permission is hereby granted, free of charge, to any person obtaining
+# a copy of this software and associated documentation files (the
+# "Software"), to deal in the Software without restriction, including
+# without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to
+# permit persons to whom the Software is furnished to do so, subject to
+# the following conditions:
+#
+# The above copyright notice and this permission notice shall be included
+# in all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
+# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
+# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+__revision__ = "src/engine/SCons/Action.py 5134 2010/08/16 23:02:40 bdeegan"
+
+import SCons.compat
+
+import dis
+import os
+# compat layer imports "cPickle" for us if it's available.
+import pickle
+import re
+import sys
+import subprocess
+
+from SCons.Debug import logInstanceCreation
+import SCons.Errors
+import SCons.Executor
+import SCons.Util
+import SCons.Subst
+
+# we use these a lot, so try to optimize them
+is_String = SCons.Util.is_String
+is_List = SCons.Util.is_List
+
+class _null(object):
+    pass
+
+print_actions = 1
+execute_actions = 1
+print_actions_presub = 0
+
+def rfile(n):
+    try:
+        return n.rfile()
+    except AttributeError:
+        return n
+
+def default_exitstatfunc(s):
+    return s
+
+try:
+    SET_LINENO = dis.SET_LINENO
+    HAVE_ARGUMENT = dis.HAVE_ARGUMENT
+except AttributeError:
+    remove_set_lineno_codes = lambda x: x
+else:
+    def remove_set_lineno_codes(code):
+        result = []
+        n = len(code)
+        i = 0
+        while i < n:
+            c = code[i]
+            op = ord(c)
+            if op >= HAVE_ARGUMENT:
+                if op != SET_LINENO:
+                    result.append(code[i:i+3])
+                i = i+3
+            else:
+                result.append(c)
+                i = i+1
+        return ''.join(result)
+
+strip_quotes = re.compile('^[\'"](.*)[\'"]$')
+
+
+def _callable_contents(obj):
+    """Return the signature contents of a callable Python object.
+    """
+    try:
+        # Test if obj is a method.
+        return _function_contents(obj.im_func)
+
+    except AttributeError:
+        try:
+            # Test if obj is a callable object.
+            return _function_contents(obj.__call__.im_func)
+
+        except AttributeError:
+            try:
+                # Test if obj is a code object.
+                return _code_contents(obj)
+
+            except AttributeError:
+                    # Test if obj is a function object.
+                    return _function_contents(obj)
+
+
+def _object_contents(obj):
+    """Return the signature contents of any Python object.
+
+    We have to handle the case where object contains a code object
+    since it can be pickled directly.
+    """
+    try:
+        # Test if obj is a method.
+        return _function_contents(obj.im_func)
+
+    except AttributeError:
+        try:
+            # Test if obj is a callable object.
+            return _function_contents(obj.__call__.im_func)
+
+        except AttributeError:
+            try:
+                # Test if obj is a code object.
+                return _code_contents(obj)
+
+            except AttributeError:
+                try:
+                    # Test if obj is a function object.
+                    return _function_contents(obj)
+
+                except AttributeError:
+                    # Should be a pickable Python object.
+                    try:
+                        return pickle.dumps(obj)
+                    except (pickle.PicklingError, TypeError):
+                        # This is weird, but it seems that nested classes
+                        # are unpickable. The Python docs say it should
+                        # always be a PicklingError, but some Python
+                        # versions seem to return TypeError.  Just do
+                        # the best we can.
+                        return str(obj)
+
+
+def _code_contents(code):
+    """Return the signature contents of a code object.
+
+    By providing direct access to the code object of the
+    function, Python makes this extremely easy.  Hooray!
+
+    Unfortunately, older versions of Python include line
+    number indications in the compiled byte code.  Boo!
+    So we remove the line number byte codes to prevent
+    recompilations from moving a Python function.
+    """
+
+    contents = []
+
+    # The code contents depends on the number of local variables
+    # but not their actual names.
+    contents.append("%s,%s" % (code.co_argcount, len(code.co_varnames)))
+    try:
+        contents.append(",%s,%s" % (len(code.co_cellvars), len(code.co_freevars)))
+    except AttributeError:
+        # Older versions of Python do not support closures.
+        contents.append(",0,0")
+
+    # The code contents depends on any constants accessed by the
+    # function. Note that we have to call _object_contents on each
+    # constants because the code object of nested functions can
+    # show-up among the constants.
+    #
+    # Note that we also always ignore the first entry of co_consts
+    # which contains the function doc string. We assume that the
+    # function does not access its doc string.
+    contents.append(',(' + ','.join(map(_object_contents,code.co_consts[1:])) + ')')
+
+    # The code contents depends on the variable names used to
+    # accessed global variable, as changing the variable name changes
+    # the variable actually accessed and therefore changes the
+    # function result.
+    contents.append(',(' + ','.join(map(_object_contents,code.co_names)) + ')')
+
+
+    # The code contents depends on its actual code!!!
+    contents.append(',(' + str(remove_set_lineno_codes(code.co_code)) + ')')
+
+    return ''.join(contents)
+
+
+def _function_contents(func):
+    """Return the signature contents of a function."""
+
+    contents = [_code_contents(func.func_code)]
+
+    # The function contents depends on the value of defaults arguments
+    if func.func_defaults:
+        contents.append(',(' + ','.join(map(_object_contents,func.func_defaults)) + ')')
+    else:
+        contents.append(',()')
+
+    # The function contents depends on the closure captured cell values.
+    try:
+        closure = func.func_closure or []
+    except AttributeError:
+        # Older versions of Python do not support closures.
+        closure = []
+
+    #xxx = [_object_contents(x.cell_contents) for x in closure]
+    try:
+        xxx = [_object_contents(x.cell_contents) for x in closure]
+    except AttributeError:
+        xxx = []
+    contents.append(',(' + ','.join(xxx) + ')')
+
+    return ''.join(contents)
+
+
+def _actionAppend(act1, act2):
+    # This function knows how to slap two actions together.
+    # Mainly, it handles ListActions by concatenating into
+    # a single ListAction.
+    a1 = Action(act1)
+    a2 = Action(act2)
+    if a1 is None or a2 is None:
+        raise TypeError("Cannot append %s to %s" % (type(act1), type(act2)))
+    if isinstance(a1, ListAction):
+        if isinstance(a2, ListAction):
+            return ListAction(a1.list + a2.list)
+        else:
+            return ListAction(a1.list + [ a2 ])
+    else:
+        if isinstance(a2, ListAction):
+            return ListAction([ a1 ] + a2.list)
+        else:
+            return ListAction([ a1, a2 ])
+
+def _do_create_keywords(args, kw):
+    """This converts any arguments after the action argument into
+    their equivalent keywords and adds them to the kw argument.
+    """
+    v = kw.get('varlist', ())
+    # prevent varlist="FOO" from being interpreted as ['F', 'O', 'O']
+    if is_String(v): v = (v,)
+    kw['varlist'] = tuple(v)
+    if args:
+        # turn positional args into equivalent keywords
+        cmdstrfunc = args[0]
+        if cmdstrfunc is None or is_String(cmdstrfunc):
+            kw['cmdstr'] = cmdstrfunc
+        elif callable(cmdstrfunc):
+            kw['strfunction'] = cmdstrfunc
+        else:
+            raise SCons.Errors.UserError(
+                'Invalid command display variable type. '
+                'You must either pass a string or a callback which '
+                'accepts (target, source, env) as parameters.')
+        if len(args) > 1:
+            kw['varlist'] = args[1:] + kw['varlist']
+    if kw.get('strfunction', _null) is not _null \
+                      and kw.get('cmdstr', _null) is not _null:
+        raise SCons.Errors.UserError(
+            'Cannot have both strfunction and cmdstr args to Action()')
+
+def _do_create_action(act, kw):
+    """This is the actual "implementation" for the
+    Action factory method, below.  This handles the
+    fact that passing lists to Action() itself has
+    different semantics than passing lists as elements
+    of lists.
+
+    The former will create a ListAction, the latter
+    will create a CommandAction by converting the inner
+    list elements to strings."""
+
+    if isinstance(act, ActionBase):
+        return act
+
+    if is_List(act):
+        return CommandAction(act, **kw)
+
+    if callable(act):
+        try:
+            gen = kw['generator']
+            del kw['generator']
+        except KeyError:
+            gen = 0
+        if gen:
+            action_type = CommandGeneratorAction
+        else:
+            action_type = FunctionAction
+        return action_type(act, kw)
+
+    if is_String(act):
+        var=SCons.Util.get_environment_var(act)
+        if var:
+            # This looks like a string that is purely an Environment
+            # variable reference, like "$FOO" or "${FOO}".  We do
+            # something special here...we lazily evaluate the contents
+            # of that Environment variable, so a user could put something
+            # like a function or a CommandGenerator in that variable
+            # instead of a string.
+            return LazyAction(var, kw)
+        commands = str(act).split('\n')
+        if len(commands) == 1:
+            return CommandAction(commands[0], **kw)
+        # The list of string commands may include a LazyAction, so we
+        # reprocess them via _do_create_list_action.
+        return _do_create_list_action(commands, kw)
+    return None
+
+def _do_create_list_action(act, kw):
+    """A factory for list actions.  Convert the input list into Actions
+    and then wrap them in a ListAction."""
+    acts = []
+    for a in act:
+        aa = _do_create_action(a, kw)
+        if aa is not None: acts.append(aa)
+    if not acts:
+        return ListAction([])
+    elif len(acts) == 1:
+        return acts[0]
+    else:
+        return ListAction(acts)
+
+def Action(act, *args, **kw):
+    """A factory for action objects."""
+    # Really simple: the _do_create_* routines do the heavy lifting.
+    _do_create_keywords(args, kw)
+    if is_List(act):
+        return _do_create_list_action(act, kw)
+    return _do_create_action(act, kw)
+
+class ActionBase(object):
+    """Base class for all types of action objects that can be held by
+    other objects (Builders, Executors, etc.)  This provides the
+    common methods for manipulating and combining those actions."""
+
+    def __cmp__(self, other):
+        return cmp(self.__dict__, other)
+
+    def no_batch_key(self, env, target, source):
+        return None
+
+    batch_key = no_batch_key
+
+    def genstring(self, target, source, env):
+        return str(self)
+
+    def get_contents(self, target, source, env):
+        result = [ self.get_presig(target, source, env) ]
+        # This should never happen, as the Action() factory should wrap
+        # the varlist, but just in case an action is created directly,
+        # we duplicate this check here.
+        vl = self.get_varlist(target, source, env)
+        if is_String(vl): vl = (vl,)
+        for v in vl:
+            result.append(env.subst('${'+v+'}'))
+        return ''.join(result)
+
+    def __add__(self, other):
+        return _actionAppend(self, other)
+
+    def __radd__(self, other):
+        return _actionAppend(other, self)
+
+    def presub_lines(self, env):
+        # CommandGeneratorAction needs a real environment
+        # in order to return the proper string here, since
+        # it may call LazyAction, which looks up a key
+        # in that env.  So we temporarily remember the env here,
+        # and CommandGeneratorAction will use this env
+        # when it calls its _generate method.
+        self.presub_env = env
+        lines = str(self).split('\n')
+        self.presub_env = None      # don't need this any more
+        return lines
+
+    def get_varlist(self, target, source, env, executor=None):
+        return self.varlist
+
+    def get_targets(self, env, executor):
+        """
+        Returns the type of targets ($TARGETS, $CHANGED_TARGETS) used
+        by this action.
+        """
+        return self.targets
+
+class _ActionAction(ActionBase):
+    """Base class for actions that create output objects."""
+    def __init__(self, cmdstr=_null, strfunction=_null, varlist=(),
+                       presub=_null, chdir=None, exitstatfunc=None,
+                       batch_key=None, targets='$TARGETS',
+                 **kw):
+        self.cmdstr = cmdstr
+        if strfunction is not _null:
+            if strfunction is None:
+                self.cmdstr = None
+            else:
+                self.strfunction = strfunction
+        self.varlist = varlist
+        self.presub = presub
+        self.chdir = chdir
+        if not exitstatfunc:
+            exitstatfunc = default_exitstatfunc
+        self.exitstatfunc = exitstatfunc
+
+        self.targets = targets
+
+        if batch_key:
+            if not callable(batch_key):
+                # They have set batch_key, but not to their own
+                # callable.  The default behavior here will batch
+                # *all* targets+sources using this action, separated
+                # for each construction environment.
+                def default_batch_key(self, env, target, source):
+                    return (id(self), id(env))
+                batch_key = default_batch_key
+            SCons.Util.AddMethod(self, batch_key, 'batch_key')
+
+    def print_cmd_line(self, s, target, source, env):
+        sys.stdout.write(s + u"\n")
+
+    def __call__(self, target, source, env,
+                               exitstatfunc=_null,
+                               presub=_null,
+                               show=_null,
+                               execute=_null,
+                               chdir=_null,
+                               executor=None):
+        if not is_List(target):
+            target = [target]
+        if not is_List(source):
+            source = [source]
+
+        if presub is _null:
+            presub = self.presub
+            if presub is _null:
+                presub = print_actions_presub
+        if exitstatfunc is _null: exitstatfunc = self.exitstatfunc
+        if show is _null:  show = print_actions
+        if execute is _null:  execute = execute_actions
+        if chdir is _null: chdir = self.chdir
+        save_cwd = None
+        if chdir:
+            save_cwd = os.getcwd()
+            try:
+                chdir = str(chdir.abspath)
+            except AttributeError:
+                if not is_String(chdir):
+                    if executor:
+                        chdir = str(executor.batches[0].targets[0].dir)
+                    else:
+                        chdir = str(target[0].dir)
+        if presub:
+            if executor:
+                target = executor.get_all_targets()
+                source = executor.get_all_sources()
+            t = ' and '.join(map(str, target))
+            l = '\n  '.join(self.presub_lines(env))
+            out = u"Building %s with action:\n  %s\n" % (t, l)
+            sys.stdout.write(out)
+        cmd = None
+        if show and self.strfunction:
+            if executor:
+                target = executor.get_all_targets()
+                source = executor.get_all_sources()
+            try:
+                cmd = self.strfunction(target, source, env, executor)
+            except TypeError:
+                cmd = self.strfunction(target, source, env)
+            if cmd:
+                if chdir:
+                    cmd = ('os.chdir(%s)\n' % repr(chdir)) + cmd
+                try:
+                    get = env.get
+                except AttributeError:
+                    print_func = self.print_cmd_line
+                else:
+                    print_func = get('PRINT_CMD_LINE_FUNC')
+                    if not print_func:
+                        print_func = self.print_cmd_line
+                print_func(cmd, target, source, env)
+        stat = 0
+        if execute:
+            if chdir:
+                os.chdir(chdir)
+            try:
+                stat = self.execute(target, source, env, executor=executor)
+                if isinstance(stat, SCons.Errors.BuildError):
+                    s = exitstatfunc(stat.status)
+                    if s:
+                        stat.status = s
+                    else:
+                        stat = s
+                else:
+                    stat = exitstatfunc(stat)
+            finally:
+                if save_cwd:
+                    os.chdir(save_cwd)
+        if cmd and save_cwd:
+            print_func('os.chdir(%s)' % repr(save_cwd), target, source, env)
+
+        return stat
+
+
+def _string_from_cmd_list(cmd_list):
+    """Takes a list of command line arguments and returns a pretty
+    representation for printing."""
+    cl = []
+    for arg in map(str, cmd_list):
+        if ' ' in arg or '\t' in arg:
+            arg = '"' + arg + '"'
+        cl.append(arg)
+    return ' '.join(cl)
+
+# A fiddlin' little function that has an 'import SCons.Environment' which
+# can't be moved to the top level without creating an import loop.  Since
+# this import creates a local variable named 'SCons', it blocks access to
+# the global variable, so we move it here to prevent complaints about local
+# variables being used uninitialized.
+default_ENV = None
+def get_default_ENV(env):
+    global default_ENV
+    try:
+        return env['ENV']
+    except KeyError:
+        if not default_ENV:
+            import SCons.Environment
+            # This is a hideously expensive way to get a default shell
+            # environment.  What it really should do is run the platform
+            # setup to get the default ENV.  Fortunately, it's incredibly
+            # rare for an Environment not to have a shell environment, so
+            # we're not going to worry about it overmuch.
+            default_ENV = SCons.Environment.Environment()['ENV']
+        return default_ENV
+
+# This function is still in draft mode.  We're going to need something like
+# it in the long run as more and more places use subprocess, but I'm sure
+# it'll have to be tweaked to get the full desired functionality.
+# one special arg (so far?), 'error', to tell what to do with exceptions.
+def _subproc(scons_env, cmd, error = 'ignore', **kw):
+    """Do common setup for a subprocess.Popen() call"""
+    # allow std{in,out,err} to be "'devnull'"
+    io = kw.get('stdin')
+    if is_String(io) and io == 'devnull':
+        kw['stdin'] = open(os.devnull)
+    io = kw.get('stdout')
+    if is_String(io) and io == 'devnull':
+        kw['stdout'] = open(os.devnull, 'w')
+    io = kw.get('stderr')
+    if is_String(io) and io == 'devnull':
+        kw['stderr'] = open(os.devnull, 'w')
+
+    # Figure out what shell environment to use
+    ENV = kw.get('env', None)
+    if ENV is None: ENV = get_default_ENV(scons_env)
+
+    # Ensure that the ENV values are all strings:
+    new_env = {}
+    for key, value in ENV.items():
+        if is_List(value):
+            # If the value is a list, then we assume it is a path list,
+            # because that's a pretty common list-like value to stick
+            # in an environment variable:
+            value = SCons.Util.flatten_sequence(value)
+            new_env[key] = os.pathsep.join(map(str, value))
+        else:
+            # It's either a string or something else.  If it's a string,
+            # we still want to call str() because it might be a *Unicode*
+            # string, which makes subprocess.Popen() gag.  If it isn't a
+            # string or a list, then we just coerce it to a string, which
+            # is the proper way to handle Dir and File instances and will
+            # produce something reasonable for just about everything else:
+            new_env[key] = str(value)
+    kw['env'] = new_env
+
+    try:
+        #FUTURE return subprocess.Popen(cmd, **kw)
+        return subprocess.Popen(cmd, **kw)
+    except EnvironmentError, e:
+        if error == 'raise': raise
+        # return a dummy Popen instance that only returns error
+        class dummyPopen(object):
+            def __init__(self, e): self.exception = e
+            def communicate(self): return ('','')
+            def wait(self): return -self.exception.errno
+            stdin = None
+            class f(object):
+                def read(self): return ''
+                def readline(self): return ''
+            stdout = stderr = f()
+        return dummyPopen(e)
+
+class CommandAction(_ActionAction):
+    """Class for command-execution actions."""
+    def __init__(self, cmd, **kw):
+        # Cmd can actually be a list or a single item; if it's a
+        # single item it should be the command string to execute; if a
+        # list then it should be the words of the command string to
+        # execute.  Only a single command should be executed by this
+        # object; lists of commands should be handled by embedding
+        # these objects in a ListAction object (which the Action()
+        # factory above does).  cmd will be passed to
+        # Environment.subst_list() for substituting environment
+        # variables.
+        if __debug__: logInstanceCreation(self, 'Action.CommandAction')
+
+        _ActionAction.__init__(self, **kw)
+        if is_List(cmd):
+            if list(filter(is_List, cmd)):
+                raise TypeError("CommandAction should be given only " \
+                      "a single command")
+        self.cmd_list = cmd
+
+    def __str__(self):
+        if is_List(self.cmd_list):
+            return ' '.join(map(str, self.cmd_list))
+        return str(self.cmd_list)
+
+    def process(self, target, source, env, executor=None):
+        if executor:
+            result = env.subst_list(self.cmd_list, 0, executor=executor)
+        else:
+            result = env.subst_list(self.cmd_list, 0, target, source)
+        silent = None
+        ignore = None
+        while True:
+            try: c = result[0][0][0]
+            except IndexError: c = None
+            if c == '@': silent = 1
+            elif c == '-': ignore = 1
+            else: break
+            result[0][0] = result[0][0][1:]
+        try:
+            if not result[0][0]:
+                result[0] = result[0][1:]
+        except IndexError:
+            pass
+        return result, ignore, silent
+
+    def strfunction(self, target, source, env, executor=None):
+        if self.cmdstr is None:
+            return None
+        if self.cmdstr is not _null:
+            from SCons.Subst import SUBST_RAW
+            if executor:
+                c = env.subst(self.cmdstr, SUBST_RAW, executor=executor)
+            else:
+                c = env.subst(self.cmdstr, SUBST_RAW, target, source)
+            if c:
+                return c
+        cmd_list, ignore, silent = self.process(target, source, env, executor)
+        if silent:
+            return ''
+        return _string_from_cmd_list(cmd_list[0])
+
+    def execute(self, target, source, env, executor=None):
+        """Execute a command action.
+
+        This will handle lists of commands as well as individual commands,
+        because construction variable substitution may turn a single
+        "command" into a list.  This means that this class can actually
+        handle lists of commands, even though that's not how we use it
+        externally.
+        """
+        escape_list = SCons.Subst.escape_list
+        flatten_sequence = SCons.Util.flatten_sequence
+
+        try:
+            shell = env['SHELL']
+        except KeyError:
+            raise SCons.Errors.UserError('Missing SHELL construction variable.')
+
+        try:
+            spawn = env['SPAWN']
+        except KeyError:
+            raise SCons.Errors.UserError('Missing SPAWN construction variable.')
+        else:
+            if is_String(spawn):
+                spawn = env.subst(spawn, raw=1, conv=lambda x: x)
+
+        escape = env.get('ESCAPE', lambda x: x)
+
+        ENV = get_default_ENV(env)
+
+        # Ensure that the ENV values are all strings:
+        for key, value in ENV.items():
+            if not is_String(value):
+                if is_List(value):
+                    # If the value is a list, then we assume it is a
+                    # path list, because that's a pretty common list-like
+                    # value to stick in an environment variable:
+                    value = flatten_sequence(value)
+                    ENV[key] = os.pathsep.join(map(str, value))
+                else:
+                    # If it isn't a string or a list, then we just coerce
+                    # it to a string, which is the proper way to handle
+                    # Dir and File instances and will produce something
+                    # reasonable for just about everything else:
+                    ENV[key] = str(value)
+
+        if executor:
+            target = executor.get_all_targets()
+            source = executor.get_all_sources()
+        cmd_list, ignore, silent = self.process(target, list(map(rfile, source)), env, executor)
+
+        # Use len() to filter out any "command" that's zero-length.
+        for cmd_line in filter(len, cmd_list):
+            # Escape the command line for the interpreter we are using.
+            cmd_line = escape_list(cmd_line, escape)
+            result = spawn(shell, escape, cmd_line[0], cmd_line, ENV)
+            if not ignore and result:
+                msg = "Error %s" % result
+                return SCons.Errors.BuildError(errstr=msg,
+                                               status=result,
+                                               action=self,
+                                               command=cmd_line)
+        return 0
+
+    def get_presig(self, target, source, env, executor=None):
+        """Return the signature contents of this action's command line.
+
+        This strips $(-$) and everything in between the string,
+        since those parts don't affect signatures.
+        """
+        from SCons.Subst import SUBST_SIG
+        cmd = self.cmd_list
+        if is_List(cmd):
+            cmd = ' '.join(map(str, cmd))
+        else:
+            cmd = str(cmd)
+        if executor:
+            return env.subst_target_source(cmd, SUBST_SIG, executor=executor)
+        else:
+            return env.subst_target_source(cmd, SUBST_SIG, target, source)
+
+    def get_implicit_deps(self, target, source, env, executor=None):
+        icd = env.get('IMPLICIT_COMMAND_DEPENDENCIES', True)
+        if is_String(icd) and icd[:1] == '$':
+            icd = env.subst(icd)
+        if not icd or icd in ('0', 'None'):
+            return []
+        from SCons.Subst import SUBST_SIG
+        if executor:
+            cmd_list = env.subst_list(self.cmd_list, SUBST_SIG, executor=executor)
+        else:
+            cmd_list = env.subst_list(self.cmd_list, SUBST_SIG, target, source)
+        res = []
+        for cmd_line in cmd_list:
+            if cmd_line:
+                d = str(cmd_line[0])
+                m = strip_quotes.match(d)
+                if m:
+                    d = m.group(1)
+                d = env.WhereIs(d)
+                if d:
+                    res.append(env.fs.File(d))
+        return res
+
+class CommandGeneratorAction(ActionBase):
+    """Class for command-generator actions."""
+    def __init__(self, generator, kw):
+        if __debug__: logInstanceCreation(self, 'Action.CommandGeneratorAction')
+        self.generator = generator
+        self.gen_kw = kw
+        self.varlist = kw.get('varlist', ())
+        self.targets = kw.get('targets', '$TARGETS')
+
+    def _generate(self, target, source, env, for_signature, executor=None):
+        # ensure that target is a list, to make it easier to write
+        # generator functions:
+        if not is_List(target):
+            target = [target]
+
+        if executor:
+            target = executor.get_all_targets()
+            source = executor.get_all_sources()
+        ret = self.generator(target=target,
+                             source=source,
+                             env=env,
+                             for_signature=for_signature)
+        gen_cmd = Action(ret, **self.gen_kw)
+        if not gen_cmd:
+            raise SCons.Errors.UserError("Object returned from command generator: %s cannot be used to create an Action." % repr(ret))
+        return gen_cmd
+
+    def __str__(self):
+        try:
+            env = self.presub_env
+        except AttributeError:
+            env = None
+        if env is None:
+            env = SCons.Defaults.DefaultEnvironment()
+        act = self._generate([], [], env, 1)
+        return str(act)
+
+    def batch_key(self, env, target, source):
+        return self._generate(target, source, env, 1).batch_key(env, target, source)
+
+    def genstring(self, target, source, env, executor=None):
+        return self._generate(target, source, env, 1, executor).genstring(target, source, env)
+
+    def __call__(self, target, source, env, exitstatfunc=_null, presub=_null,
+                 show=_null, execute=_null, chdir=_null, executor=None):
+        act = self._generate(target, source, env, 0, executor)
+        if act is None:
+            raise UserError("While building `%s': "
+                            "Cannot deduce file extension from source files: %s"
+                % (repr(list(map(str, target))), repr(list(map(str, source)))))
+        return act(target, source, env, exitstatfunc, presub,
+                   show, execute, chdir, executor)
+
+    def get_presig(self, target, source, env, executor=None):
+        """Return the signature contents of this action's command line.
+
+        This strips $(-$) and everything in between the string,
+        since those parts don't affect signatures.
+        """
+        return self._generate(target, source, env, 1, executor).get_presig(target, source, env)
+
+    def get_implicit_deps(self, target, source, env, executor=None):
+        return self._generate(target, source, env, 1, executor).get_implicit_deps(target, source, env)
+
+    def get_varlist(self, target, source, env, executor=None):
+        return self._generate(target, source, env, 1, executor).get_varlist(target, source, env, executor)
+
+    def get_targets(self, env, executor):
+        return self._generate(None, None, env, 1, executor).get_targets(env, executor)
+
+
+
+# A LazyAction is a kind of hybrid generator and command action for
+# strings of the form "$VAR".  These strings normally expand to other
+# strings (think "$CCCOM" to "$CC -c -o $TARGET $SOURCE"), but we also
+# want to be able to replace them with functions in the construction
+# environment.  Consequently, we want lazy evaluation and creation of
+# an Action in the case of the function, but that's overkill in the more
+# normal case of expansion to other strings.
+#
+# So we do this with a subclass that's both a generator *and*
+# a command action.  The overridden methods all do a quick check
+# of the construction variable, and if it's a string we just call
+# the corresponding CommandAction method to do the heavy lifting.
+# If not, then we call the same-named CommandGeneratorAction method.
+# The CommandGeneratorAction methods work by using the overridden
+# _generate() method, that is, our own way of handling "generation" of
+# an action based on what's in the construction variable.
+
+class LazyAction(CommandGeneratorAction, CommandAction):
+
+    def __init__(self, var, kw):
+        if __debug__: logInstanceCreation(self, 'Action.LazyAction')
+        #FUTURE CommandAction.__init__(self, '${'+var+'}', **kw)
+        CommandAction.__init__(self, '${'+var+'}', **kw)
+        self.var = SCons.Util.to_String(var)
+        self.gen_kw = kw
+
+    def get_parent_class(self, env):
+        c = env.get(self.var)
+        if is_String(c) and not '\n' in c:
+            return CommandAction
+        return CommandGeneratorAction
+
+    def _generate_cache(self, env):
+        if env:
+            c = env.get(self.var, '')
+        else:
+            c = ''
+        gen_cmd = Action(c, **self.gen_kw)
+        if not gen_cmd:
+            raise SCons.Errors.UserError("$%s value %s cannot be used to create an Action." % (self.var, repr(c)))
+        return gen_cmd
+
+    def _generate(self, target, source, env, for_signature, executor=None):
+        return self._generate_cache(env)
+
+    def __call__(self, target, source, env, *args, **kw):
+        c = self.get_parent_class(env)
+        return c.__call__(self, target, source, env, *args, **kw)
+
+    def get_presig(self, target, source, env):
+        c = self.get_parent_class(env)
+        return c.get_presig(self, target, source, env)
+
+    def get_varlist(self, target, source, env, executor=None):
+        c = self.get_parent_class(env)
+        return c.get_varlist(self, target, source, env, executor)
+
+
+class FunctionAction(_ActionAction):
+    """Class for Python function actions."""
+
+    def __init__(self, execfunction, kw):
+        if __debug__: logInstanceCreation(self, 'Action.FunctionAction')
+
+        self.execfunction = execfunction
+        try:
+            self.funccontents = _callable_contents(execfunction)
+        except AttributeError:
+            try:
+                # See if execfunction will do the heavy lifting for us.
+                self.gc = execfunction.get_contents
+            except AttributeError:
+                # This is weird, just do the best we can.
+                self.funccontents = _object_contents(execfunction)
+
+        _ActionAction.__init__(self, **kw)
+
+    def function_name(self):
+        try:
+            return self.execfunction.__name__
+        except AttributeError:
+            try:
+                return self.execfunction.__class__.__name__
+            except AttributeError:
+                return "unknown_python_function"
+
+    def strfunction(self, target, source, env, executor=None):
+        if self.cmdstr is None:
+            return None
+        if self.cmdstr is not _null:
+            from SCons.Subst import SUBST_RAW
+            if executor:
+                c = env.subst(self.cmdstr, SUBST_RAW, executor=executor)
+            else:
+                c = env.subst(self.cmdstr, SUBST_RAW, target, source)
+            if c:
+                return c
+        def array(a):
+            def quote(s):
+                try:
+                    str_for_display = s.str_for_display
+                except AttributeError:
+                    s = repr(s)
+                else:
+                    s = str_for_display()
+                return s
+            return '[' + ", ".join(map(quote, a)) + ']'
+        try:
+            strfunc = self.execfunction.strfunction
+        except AttributeError:
+            pass
+        else:
+            if strfunc is None:
+                return None
+            if callable(strfunc):
+                return strfunc(target, source, env)
+        name = self.function_name()
+        tstr = array(target)
+        sstr = array(source)
+        return "%s(%s, %s)" % (name, tstr, sstr)
+
+    def __str__(self):
+        name = self.function_name()
+        if name == 'ActionCaller':
+            return str(self.execfunction)
+        return "%s(target, source, env)" % name
+
+    def execute(self, target, source, env, executor=None):
+        exc_info = (None,None,None)
+        try:
+            if executor:
+                target = executor.get_all_targets()
+                source = executor.get_all_sources()
+            rsources = list(map(rfile, source))
+            try:
+                result = self.execfunction(target=target, source=rsources, env=env)
+            except KeyboardInterrupt, e:
+                raise
+            except SystemExit, e:
+                raise
+            except Exception, e:
+                result = e
+                exc_info = sys.exc_info()
+
+            if result:
+                result = SCons.Errors.convert_to_BuildError(result, exc_info)
+                result.node=target
+                result.action=self
+                try:
+                    result.command=self.strfunction(target, source, env, executor)
+                except TypeError:
+                    result.command=self.strfunction(target, source, env)
+
+                # FIXME: This maintains backward compatibility with respect to
+                # which type of exceptions were returned by raising an
+                # exception and which ones were returned by value. It would
+                # probably be best to always return them by value here, but
+                # some codes do not check the return value of Actions and I do
+                # not have the time to modify them at this point.
+                if (exc_info[1] and
+                    not isinstance(exc_info[1],EnvironmentError)):
+                    raise result
+
+            return result
+        finally:
+            # Break the cycle between the traceback object and this
+            # function stack frame. See the sys.exc_info() doc info for
+            # more information about this issue.
+            del exc_info
+
+
+    def get_presig(self, target, source, env):
+        """Return the signature contents of this callable action."""
+        try:
+            return self.gc(target, source, env)
+        except AttributeError:
+            return self.funccontents
+
+    def get_implicit_deps(self, target, source, env):
+        return []
+
+class ListAction(ActionBase):
+    """Class for lists of other actions."""
+    def __init__(self, actionlist):
+        if __debug__: logInstanceCreation(self, 'Action.ListAction')
+        def list_of_actions(x):
+            if isinstance(x, ActionBase):
+                return x
+            return Action(x)
+        self.list = list(map(list_of_actions, actionlist))
+        # our children will have had any varlist
+        # applied; we don't need to do it again
+        self.varlist = ()
+        self.targets = '$TARGETS'
+
+    def genstring(self, target, source, env):
+        return '\n'.join([a.genstring(target, source, env) for a in self.list])
+
+    def __str__(self):
+        return '\n'.join(map(str, self.list))
+
+    def presub_lines(self, env):
+        return SCons.Util.flatten_sequence(
+            [a.presub_lines(env) for a in self.list])
+
+    def get_presig(self, target, source, env):
+        """Return the signature contents of this action list.
+
+        Simple concatenation of the signatures of the elements.
+        """
+        return "".join([x.get_contents(target, source, env) for x in self.list])
+
+    def __call__(self, target, source, env, exitstatfunc=_null, presub=_null,
+                 show=_null, execute=_null, chdir=_null, executor=None):
+        if executor:
+            target = executor.get_all_targets()
+            source = executor.get_all_sources()
+        for act in self.list:
+            stat = act(target, source, env, exitstatfunc, presub,
+                       show, execute, chdir, executor)
+            if stat:
+                return stat
+        return 0
+
+    def get_implicit_deps(self, target, source, env):
+        result = []
+        for act in self.list:
+            result.extend(act.get_implicit_deps(target, source, env))
+        return result
+
+    def get_varlist(self, target, source, env, executor=None):
+        result = SCons.Util.OrderedDict()
+        for act in self.list:
+            for var in act.get_varlist(target, source, env, executor):
+                result[var] = True
+        return list(result.keys())
+
+class ActionCaller(object):
+    """A class for delaying calling an Action function with specific
+    (positional and keyword) arguments until the Action is actually
+    executed.
+
+    This class looks to the rest of the world like a normal Action object,
+    but what it's really doing is hanging on to the arguments until we
+    have a target, source and env to use for the expansion.
+    """
+    def __init__(self, parent, args, kw):
+        self.parent = parent
+        self.args = args
+        self.kw = kw
+
+    def get_contents(self, target, source, env):
+        actfunc = self.parent.actfunc
+        try:
+            # "self.actfunc" is a function.
+            contents = str(actfunc.func_code.co_code)
+        except AttributeError:
+            # "self.actfunc" is a callable object.
+            try:
+                contents = str(actfunc.__call__.im_func.func_code.co_code)
+            except AttributeError:
+                # No __call__() method, so it might be a builtin
+                # or something like that.  Do the best we can.
+                contents = str(actfunc)
+        contents = remove_set_lineno_codes(contents)
+        return contents
+
+    def subst(self, s, target, source, env):
+        # If s is a list, recursively apply subst()
+        # to every element in the list
+        if is_List(s):
+            result = []
+            for elem in s:
+                result.append(self.subst(elem, target, source, env))
+            return self.parent.convert(result)
+
+        # Special-case hack:  Let a custom function wrapped in an
+        # ActionCaller get at the environment through which the action
+        # was called by using this hard-coded value as a special return.
+        if s == '$__env__':
+            return env
+        elif is_String(s):
+            return env.subst(s, 1, target, source)
+        return self.parent.convert(s)
+
+    def subst_args(self, target, source, env):
+        return [self.subst(x, target, source, env) for x in self.args]
+
+    def subst_kw(self, target, source, env):
+        kw = {}
+        for key in self.kw.keys():
+            kw[key] = self.subst(self.kw[key], target, source, env)
+        return kw
+
+    def __call__(self, target, source, env, executor=None):
+        args = self.subst_args(target, source, env)
+        kw = self.subst_kw(target, source, env)
+        return self.parent.actfunc(*args, **kw)
+
+    def strfunction(self, target, source, env):
+        args = self.subst_args(target, source, env)
+        kw = self.subst_kw(target, source, env)
+        return self.parent.strfunc(*args, **kw)
+
+    def __str__(self):
+        return self.parent.strfunc(*self.args, **self.kw)
+
+class ActionFactory(object):
+    """A factory class that will wrap up an arbitrary function
+    as an SCons-executable Action object.
+
+    The real heavy lifting here is done by the ActionCaller class.
+    We just collect the (positional and keyword) arguments that we're
+    called with and give them to the ActionCaller object we create,
+    so it can hang onto them until it needs them.
+    """
+    def __init__(self, actfunc, strfunc, convert=lambda x: x):
+        self.actfunc = actfunc
+        self.strfunc = strfunc
+        self.convert = convert
+
+    def __call__(self, *args, **kw):
+        ac = ActionCaller(self, args, kw)
+        action = Action(ac, strfunction=ac.strfunction)
+        return action
+
+# Local Variables:
+# tab-width:4
+# indent-tabs-mode:nil
+# End:
+# vim: set expandtab tabstop=4 shiftwidth=4: