Source code for SCons.Builder

# MIT License
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# Copyright The SCons Foundation
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"""
SCons.Builder

Builder object subsystem.

A Builder object is a callable that encapsulates information about how
to execute actions to create a target Node (file) from source Nodes
(files), and how to create those dependencies for tracking.

The main entry point here is the Builder() factory method.  This provides
a procedural interface that creates the right underlying Builder object
based on the keyword arguments supplied and the types of the arguments.

The goal is for this external interface to be simple enough that the
vast majority of users can create new Builders as necessary to support
building new types of files in their configurations, without having to
dive any deeper into this subsystem.

The base class here is BuilderBase.  This is a concrete base class which
does, in fact, represent the Builder objects that we (or users) create.

There is also a proxy that looks like a Builder:

    CompositeBuilder

        This proxies for a Builder with an action that is actually a
        dictionary that knows how to map file suffixes to a specific
        action.  This is so that we can invoke different actions
        (compilers, compile options) for different flavors of source
        files.

Builders and their proxies have the following public interface methods
used by other modules:

    - __call__()
        THE public interface.  Calling a Builder object (with the
        use of internal helper methods) sets up the target and source
        dependencies, appropriate mapping to a specific action, and the
        environment manipulation necessary for overridden construction
        variable.  This also takes care of warning about possible mistakes
        in keyword arguments.

    - add_emitter()
        Adds an emitter for a specific file suffix, used by some Tool
        modules to specify that (for example) a yacc invocation on a .y
        can create a .h *and* a .c file.

    - add_action()
        Adds an action for a specific file suffix, heavily used by
        Tool modules to add their specific action(s) for turning
        a source file into an object file to the global static
        and shared object file Builders.

There are the following methods for internal use within this module:

    - _execute()
        The internal method that handles the heavily lifting when a
        Builder is called.  This is used so that the __call__() methods
        can set up warning about possible mistakes in keyword-argument
        overrides, and *then* execute all of the steps necessary so that
        the warnings only occur once.

    - get_name()
        Returns the Builder's name within a specific Environment,
        primarily used to try to return helpful information in error
        messages.

    - adjust_suffix()
    - get_prefix()
    - get_suffix()
    - get_src_suffix()
    - set_src_suffix()
        Miscellaneous stuff for handling the prefix and suffix
        manipulation we use in turning source file names into target
        file names.

"""

from collections import UserDict, UserList

import SCons.Action
import SCons.Debug
from SCons.Debug import logInstanceCreation
from SCons.Errors import InternalError, UserError
import SCons.Executor
import SCons.Memoize
import SCons.Util
import SCons.Warnings

[docs]class _Null: pass
_null = _Null
[docs]def match_splitext(path, suffixes = []): if suffixes: matchsuf = [S for S in suffixes if path[-len(S):] == S] if matchsuf: suf = max([(len(_f),_f) for _f in matchsuf])[1] return [path[:-len(suf)], path[-len(suf):]] return SCons.Util.splitext(path)
[docs]class DictCmdGenerator(SCons.Util.Selector): """This is a callable class that can be used as a command generator function. It holds on to a dictionary mapping file suffixes to Actions. It uses that dictionary to return the proper action based on the file suffix of the source file.""" def __init__(self, dict=None, source_ext_match=1): SCons.Util.Selector.__init__(self, dict) self.source_ext_match = source_ext_match
[docs] def src_suffixes(self): return list(self.keys())
[docs] def add_action(self, suffix, action): """Add a suffix-action pair to the mapping. """ self[suffix] = action
def __call__(self, target, source, env, for_signature): if not source: return [] if self.source_ext_match: suffixes = self.src_suffixes() ext = None for src in map(str, source): my_ext = match_splitext(src, suffixes)[1] if ext and my_ext != ext: raise UserError("While building `%s' from `%s': Cannot build multiple sources with different extensions: %s, %s" % (repr(list(map(str, target))), src, ext, my_ext)) ext = my_ext else: ext = match_splitext(str(source[0]), self.src_suffixes())[1] if not ext: #return ext raise UserError("While building `%s': " "Cannot deduce file extension from source files: %s" % (repr(list(map(str, target))), repr(list(map(str, source))))) try: ret = SCons.Util.Selector.__call__(self, env, source, ext) except KeyError as e: raise UserError("Ambiguous suffixes after environment substitution: %s == %s == %s" % (e.args[0], e.args[1], e.args[2])) if ret is None: raise UserError("While building `%s' from `%s': Don't know how to build from a source file with suffix `%s'. Expected a suffix in this list: %s." % \ (repr(list(map(str, target))), repr(list(map(str, source))), ext, repr(list(self.keys())))) return ret
[docs]class CallableSelector(SCons.Util.Selector): """A callable dictionary that will, in turn, call the value it finds if it can.""" def __call__(self, env, source): value = SCons.Util.Selector.__call__(self, env, source) if callable(value): value = value(env, source) return value
[docs]class DictEmitter(SCons.Util.Selector): """A callable dictionary that maps file suffixes to emitters. When called, it finds the right emitter in its dictionary for the suffix of the first source file, and calls that emitter to get the right lists of targets and sources to return. If there's no emitter for the suffix in its dictionary, the original target and source are returned. """ def __call__(self, target, source, env): emitter = SCons.Util.Selector.__call__(self, env, source) if emitter: target, source = emitter(target, source, env) return (target, source)
[docs]class ListEmitter(UserList): """A callable list of emitters that calls each in sequence, returning the result. """ def __call__(self, target, source, env): for e in self.data: target, source = e(target, source, env) return (target, source)
# These are a common errors when calling a Builder; # they are similar to the 'target' and 'source' keyword args to builders, # so we issue warnings when we see them. The warnings can, of course, # be disabled. misleading_keywords = { 'targets' : 'target', 'sources' : 'source', }
[docs]class OverrideWarner(UserDict): """A class for warning about keyword arguments that we use as overrides in a Builder call. This class exists to handle the fact that a single Builder call can actually invoke multiple builders. This class only emits the warnings once, no matter how many Builders are invoked. """ def __init__(self, dict): UserDict.__init__(self, dict) if SCons.Debug.track_instances: logInstanceCreation(self, 'Builder.OverrideWarner') self.already_warned = None
[docs] def warn(self): if self.already_warned: return for k in self.keys(): if k in misleading_keywords: alt = misleading_keywords[k] msg = "Did you mean to use `%s' instead of `%s'?" % (alt, k) SCons.Warnings.warn(SCons.Warnings.MisleadingKeywordsWarning, msg) self.already_warned = 1
[docs]def Builder(**kw): """A factory for builder objects.""" composite = None if 'generator' in kw: if 'action' in kw: raise UserError("You must not specify both an action and a generator.") kw['action'] = SCons.Action.CommandGeneratorAction(kw['generator'], {}) del kw['generator'] elif 'action' in kw: source_ext_match = kw.get('source_ext_match', 1) if 'source_ext_match' in kw: del kw['source_ext_match'] if SCons.Util.is_Dict(kw['action']): composite = DictCmdGenerator(kw['action'], source_ext_match) kw['action'] = SCons.Action.CommandGeneratorAction(composite, {}) kw['src_suffix'] = composite.src_suffixes() else: kw['action'] = SCons.Action.Action(kw['action']) if 'emitter' in kw: emitter = kw['emitter'] if SCons.Util.is_String(emitter): # This allows users to pass in an Environment # variable reference (like "$FOO") as an emitter. # We will look in that Environment variable for # a callable to use as the actual emitter. var = SCons.Util.get_environment_var(emitter) if not var: raise UserError("Supplied emitter '%s' does not appear to refer to an Environment variable" % emitter) kw['emitter'] = EmitterProxy(var) elif SCons.Util.is_Dict(emitter): kw['emitter'] = DictEmitter(emitter) elif SCons.Util.is_List(emitter): kw['emitter'] = ListEmitter(emitter) result = BuilderBase(**kw) if composite is not None: result = CompositeBuilder(result, composite) return result
[docs]def _node_errors(builder, env, tlist, slist): """Validate that the lists of target and source nodes are legal for this builder and environment. Raise errors or issue warnings as appropriate. """ # First, figure out if there are any errors in the way the targets # were specified. for t in tlist: if t.side_effect: raise UserError("Multiple ways to build the same target were specified for: %s" % t) if t.has_explicit_builder(): # Check for errors when the environments are different # No error if environments are the same Environment instance if (t.env is not None and t.env is not env and # Check OverrideEnvironment case - no error if wrapped Environments # are the same instance, and overrides lists match not (getattr(t.env, '__subject', 0) is getattr(env, '__subject', 1) and getattr(t.env, 'overrides', 0) == getattr(env, 'overrides', 1) and not builder.multi)): action = t.builder.action t_contents = t.builder.action.get_contents(tlist, slist, t.env) contents = builder.action.get_contents(tlist, slist, env) if t_contents == contents: msg = "Two different environments were specified for target %s,\n\tbut they appear to have the same action: %s" % (t, action.genstring(tlist, slist, t.env)) SCons.Warnings.warn(SCons.Warnings.DuplicateEnvironmentWarning, msg) else: try: msg = "Two environments with different actions were specified for the same target: %s\n(action 1: %s)\n(action 2: %s)" % (t,t_contents.decode('utf-8'),contents.decode('utf-8')) except UnicodeDecodeError: msg = "Two environments with different actions were specified for the same target: %s"%t raise UserError(msg) if builder.multi: if t.builder != builder: msg = "Two different builders (%s and %s) were specified for the same target: %s" % (t.builder.get_name(env), builder.get_name(env), t) raise UserError(msg) # TODO(batch): list constructed each time! if t.get_executor().get_all_targets() != tlist: msg = "Two different target lists have a target in common: %s (from %s and from %s)" % (t, list(map(str, t.get_executor().get_all_targets())), list(map(str, tlist))) raise UserError(msg) elif t.sources != slist: msg = "Multiple ways to build the same target were specified for: %s (from %s and from %s)" % (t, list(map(str, t.sources)), list(map(str, slist))) raise UserError(msg) if builder.single_source: if len(slist) > 1: raise UserError("More than one source given for single-source builder: targets=%s sources=%s" % (list(map(str,tlist)), list(map(str,slist))))
[docs]class EmitterProxy: """This is a callable class that can act as a Builder emitter. It holds on to a string that is a key into an Environment dictionary, and will look there at actual build time to see if it holds a callable. If so, we will call that as the actual emitter.""" def __init__(self, var): self.var = SCons.Util.to_String(var) def __call__(self, target, source, env): emitter = self.var # Recursively substitute the variable. # We can't use env.subst() because it deals only # in strings. Maybe we should change that? while SCons.Util.is_String(emitter) and emitter in env: emitter = env[emitter] if callable(emitter): target, source = emitter(target, source, env) elif SCons.Util.is_List(emitter): for e in emitter: target, source = e(target, source, env) return (target, source) def __eq__(self, other): return self.var == other.var def __lt__(self, other): return self.var < other.var
[docs]class BuilderBase: """Base class for Builders, objects that create output nodes (files) from input nodes (files). """ def __init__(self, action = None, prefix = '', suffix = '', src_suffix = '', target_factory = None, source_factory = None, target_scanner = None, source_scanner = None, emitter = None, multi = 0, env = None, single_source = 0, name = None, chdir = _null, is_explicit = 1, src_builder = None, ensure_suffix = False, **overrides): if SCons.Debug.track_instances: logInstanceCreation(self, 'Builder.BuilderBase') self._memo = {} self.action = action self.multi = multi if SCons.Util.is_Dict(prefix): prefix = CallableSelector(prefix) self.prefix = prefix if SCons.Util.is_Dict(suffix): suffix = CallableSelector(suffix) self.env = env self.single_source = single_source if 'overrides' in overrides: msg = "The \"overrides\" keyword to Builder() creation has been removed;\n" +\ "\tspecify the items as keyword arguments to the Builder() call instead." raise TypeError(msg) if 'scanner' in overrides: msg = "The \"scanner\" keyword to Builder() creation has been removed;\n" +\ "\tuse: source_scanner or target_scanner as appropriate." raise TypeError(msg) self.overrides = overrides self.set_suffix(suffix) self.set_src_suffix(src_suffix) self.ensure_suffix = ensure_suffix self.target_factory = target_factory self.source_factory = source_factory self.target_scanner = target_scanner self.source_scanner = source_scanner self.emitter = emitter # Optional Builder name should only be used for Builders # that don't get attached to construction environments. if name: self.name = name self.executor_kw = {} if chdir is not _null: self.executor_kw['chdir'] = chdir self.is_explicit = is_explicit if src_builder is None: src_builder = [] elif not SCons.Util.is_List(src_builder): src_builder = [ src_builder ] self.src_builder = src_builder def __bool__(self): raise InternalError("Do not test for the Node.builder attribute directly; use Node.has_builder() instead")
[docs] def get_name(self, env): """Attempts to get the name of the Builder. Look at the BUILDERS variable of env, expecting it to be a dictionary containing this Builder, and return the key of the dictionary. If there's no key, then return a directly-configured name (if there is one) or the name of the class (by default).""" try: index = list(env['BUILDERS'].values()).index(self) return list(env['BUILDERS'].keys())[index] except (AttributeError, KeyError, TypeError, ValueError): try: return self.name except AttributeError: return str(self.__class__)
def __eq__(self, other): return self.__dict__ == other.__dict__
[docs] def splitext(self, path, env=None): if not env: env = self.env if env: suffixes = self.src_suffixes(env) else: suffixes = [] return match_splitext(path, suffixes)
[docs] def _adjustixes(self, files, pre, suf, ensure_suffix=False): if not files: return [] result = [] if not SCons.Util.is_List(files): files = [files] for f in files: if SCons.Util.is_String(f): f = SCons.Util.adjustixes(f, pre, suf, ensure_suffix) result.append(f) return result
[docs] def _create_nodes(self, env, target = None, source = None): """Create and return lists of target and source nodes. """ src_suf = self.get_src_suffix(env) target_factory = env.get_factory(self.target_factory) source_factory = env.get_factory(self.source_factory) source = self._adjustixes(source, None, src_suf) slist = env.arg2nodes(source, source_factory) pre = self.get_prefix(env, slist) suf = self.get_suffix(env, slist) if target is None: try: t_from_s = slist[0].target_from_source except AttributeError: raise UserError("Do not know how to create a target from source `%s'" % slist[0]) except IndexError: tlist = [] else: splitext = lambda S: self.splitext(S,env) tlist = [ t_from_s(pre, suf, splitext) ] else: # orig_target = target target = self._adjustixes(target, pre, suf, self.ensure_suffix) tlist = env.arg2nodes(target, target_factory, target=target, source=source) if self.emitter: # The emitter is going to do str(node), but because we're # being called *from* a builder invocation, the new targets # don't yet have a builder set on them and will look like # source files. Fool the emitter's str() calls by setting # up a temporary builder on the new targets. new_targets = [] for t in tlist: if not t.is_derived(): t.builder_set(self) new_targets.append(t) orig_tlist = tlist[:] orig_slist = slist[:] target, source = self.emitter(target=tlist, source=slist, env=env) # Now delete the temporary builders that we attached to any # new targets, so that _node_errors() doesn't do weird stuff # to them because it thinks they already have builders. for t in new_targets: if t.builder is self: # Only delete the temporary builder if the emitter # didn't change it on us. t.builder_set(None) # Have to call arg2nodes yet again, since it is legal for # emitters to spit out strings as well as Node instances. tlist = env.arg2nodes(target, target_factory, target=orig_tlist, source=orig_slist) slist = env.arg2nodes(source, source_factory, target=orig_tlist, source=orig_slist) return tlist, slist
[docs] def _execute(self, env, target, source, overwarn={}, executor_kw={}): # We now assume that target and source are lists or None. if self.src_builder: source = self.src_builder_sources(env, source, overwarn) if self.single_source and len(source) > 1 and target is None: result = [] if target is None: target = [None]*len(source) for tgt, src in zip(target, source): if tgt is not None: tgt = [tgt] if src is not None: src = [src] result.extend(self._execute(env, tgt, src, overwarn)) return SCons.Node.NodeList(result) overwarn.warn() tlist, slist = self._create_nodes(env, target, source) # If there is more than one target ensure that if we need to reset # the implicit list to new scan of dependency all targets implicit lists # are cleared. (SCons GH Issue #2811 and MongoDB SERVER-33111) if len(tlist) > 1: for t in tlist: t.target_peers = tlist # Check for errors with the specified target/source lists. _node_errors(self, env, tlist, slist) # The targets are fine, so find or make the appropriate Executor to # build this particular list of targets from this particular list of # sources. executor = None key = None if self.multi: try: executor = tlist[0].get_executor(create = 0) except (AttributeError, IndexError): pass else: executor.add_sources(slist) if executor is None: if not self.action: fmt = "Builder %s must have an action to build %s." raise UserError(fmt % (self.get_name(env or self.env), list(map(str,tlist)))) key = self.action.batch_key(env or self.env, tlist, slist) if key: try: executor = SCons.Executor.GetBatchExecutor(key) except KeyError: pass else: executor.add_batch(tlist, slist) if executor is None: executor = SCons.Executor.Executor(self.action, env, [], tlist, slist, executor_kw) if key: SCons.Executor.AddBatchExecutor(key, executor) # Now set up the relevant information in the target Nodes themselves. for t in tlist: t.cwd = env.fs.getcwd() t.builder_set(self) t.env_set(env) t.add_source(slist) t.set_executor(executor) t.set_explicit(self.is_explicit) return SCons.Node.NodeList(tlist)
def __call__(self, env, target=None, source=None, chdir=_null, **kw): # We now assume that target and source are lists or None. # The caller (typically Environment.BuilderWrapper) is # responsible for converting any scalar values to lists. if chdir is _null: ekw = self.executor_kw else: ekw = self.executor_kw.copy() ekw['chdir'] = chdir if 'chdir' in ekw and SCons.Util.is_String(ekw['chdir']): ekw['chdir'] = env.subst(ekw['chdir']) if kw: if 'srcdir' in kw: def prependDirIfRelative(f, srcdir=kw['srcdir']): import os.path if SCons.Util.is_String(f) and not os.path.isabs(f): f = os.path.join(srcdir, f) return f if not SCons.Util.is_List(source): source = [source] source = list(map(prependDirIfRelative, source)) del kw['srcdir'] if self.overrides: env_kw = self.overrides.copy() env_kw.update(kw) else: env_kw = kw else: env_kw = self.overrides # TODO if env_kw: then the following line. there's no purpose in calling if no overrides. env = env.Override(env_kw) return self._execute(env, target, source, OverrideWarner(kw), ekw)
[docs] def adjust_suffix(self, suff): if suff and not suff[0] in [ '.', '_', '$' ]: return '.' + suff return suff
[docs] def get_prefix(self, env, sources=[]): prefix = self.prefix if callable(prefix): prefix = prefix(env, sources) return env.subst(prefix)
[docs] def set_suffix(self, suffix): if not callable(suffix): suffix = self.adjust_suffix(suffix) self.suffix = suffix
[docs] def get_suffix(self, env, sources=[]): suffix = self.suffix if callable(suffix): suffix = suffix(env, sources) return env.subst(suffix)
[docs] def set_src_suffix(self, src_suffix): if not src_suffix: src_suffix = [] elif not SCons.Util.is_List(src_suffix): src_suffix = [ src_suffix ] self.src_suffix = [callable(suf) and suf or self.adjust_suffix(suf) for suf in src_suffix]
[docs] def get_src_suffix(self, env): """Get the first src_suffix in the list of src_suffixes.""" ret = self.src_suffixes(env) if not ret: return '' return ret[0]
[docs] def add_emitter(self, suffix, emitter): """Add a suffix-emitter mapping to this Builder. This assumes that emitter has been initialized with an appropriate dictionary type, and will throw a TypeError if not, so the caller is responsible for knowing that this is an appropriate method to call for the Builder in question. """ self.emitter[suffix] = emitter
[docs] def add_src_builder(self, builder): """ Add a new Builder to the list of src_builders. This requires wiping out cached values so that the computed lists of source suffixes get re-calculated. """ self._memo = {} self.src_builder.append(builder)
[docs] def _get_sdict(self, env): """ Returns a dictionary mapping all of the source suffixes of all src_builders of this Builder to the underlying Builder that should be called first. This dictionary is used for each target specified, so we save a lot of extra computation by memoizing it for each construction environment. Note that this is re-computed each time, not cached, because there might be changes to one of our source Builders (or one of their source Builders, and so on, and so on...) that we can't "see." The underlying methods we call cache their computed values, though, so we hope repeatedly aggregating them into a dictionary like this won't be too big a hit. We may need to look for a better way to do this if performance data show this has turned into a significant bottleneck. """ sdict = {} for bld in self.get_src_builders(env): for suf in bld.src_suffixes(env): sdict[suf] = bld return sdict
[docs] def src_builder_sources(self, env, source, overwarn={}): sdict = self._get_sdict(env) src_suffixes = self.src_suffixes(env) lengths = list(set(map(len, src_suffixes))) def match_src_suffix(name, src_suffixes=src_suffixes, lengths=lengths): node_suffixes = [name[-l:] for l in lengths] for suf in src_suffixes: if suf in node_suffixes: return suf return None result = [] for s in SCons.Util.flatten(source): if SCons.Util.is_String(s): match_suffix = match_src_suffix(env.subst(s)) if not match_suffix and '.' not in s: src_suf = self.get_src_suffix(env) s = self._adjustixes(s, None, src_suf)[0] else: match_suffix = match_src_suffix(s.name) if match_suffix: try: bld = sdict[match_suffix] except KeyError: result.append(s) else: tlist = bld._execute(env, None, [s], overwarn) # If the subsidiary Builder returned more than one # target, then filter out any sources that this # Builder isn't capable of building. if len(tlist) > 1: tlist = [t for t in tlist if match_src_suffix(t.name)] result.extend(tlist) else: result.append(s) source_factory = env.get_factory(self.source_factory) return env.arg2nodes(result, source_factory)
[docs] def _get_src_builders_key(self, env): return id(env)
[docs] @SCons.Memoize.CountDictCall(_get_src_builders_key) def get_src_builders(self, env): """ Returns the list of source Builders for this Builder. This exists mainly to look up Builders referenced as strings in the 'BUILDER' variable of the construction environment and cache the result. """ memo_key = id(env) try: memo_dict = self._memo['get_src_builders'] except KeyError: memo_dict = {} self._memo['get_src_builders'] = memo_dict else: try: return memo_dict[memo_key] except KeyError: pass builders = [] for bld in self.src_builder: if SCons.Util.is_String(bld): try: bld = env['BUILDERS'][bld] except KeyError: continue builders.append(bld) memo_dict[memo_key] = builders return builders
[docs] def _subst_src_suffixes_key(self, env): return id(env)
[docs] @SCons.Memoize.CountDictCall(_subst_src_suffixes_key) def subst_src_suffixes(self, env): """ The suffix list may contain construction variable expansions, so we have to evaluate the individual strings. To avoid doing this over and over, we memoize the results for each construction environment. """ memo_key = id(env) try: memo_dict = self._memo['subst_src_suffixes'] except KeyError: memo_dict = {} self._memo['subst_src_suffixes'] = memo_dict else: try: return memo_dict[memo_key] except KeyError: pass suffixes = [env.subst(x) for x in self.src_suffix] memo_dict[memo_key] = suffixes return suffixes
[docs] def src_suffixes(self, env): """ Returns the list of source suffixes for all src_builders of this Builder. This is essentially a recursive descent of the src_builder "tree." (This value isn't cached because there may be changes in a src_builder many levels deep that we can't see.) """ sdict = {} suffixes = self.subst_src_suffixes(env) for s in suffixes: sdict[s] = 1 for builder in self.get_src_builders(env): for s in builder.src_suffixes(env): if s not in sdict: sdict[s] = 1 suffixes.append(s) return suffixes
[docs]class CompositeBuilder(SCons.Util.Proxy): """A Builder Proxy whose main purpose is to always have a DictCmdGenerator as its action, and to provide access to the DictCmdGenerator's add_action() method. """ def __init__(self, builder, cmdgen): if SCons.Debug.track_instances: logInstanceCreation(self, 'Builder.CompositeBuilder') SCons.Util.Proxy.__init__(self, builder) # cmdgen should always be an instance of DictCmdGenerator. self.cmdgen = cmdgen self.builder = builder __call__ = SCons.Util.Delegate('__call__')
[docs] def add_action(self, suffix, action): self.cmdgen.add_action(suffix, action) self.set_src_suffix(self.cmdgen.src_suffixes())
[docs]def is_a_Builder(obj): """"Returns True if the specified obj is one of our Builder classes. The test is complicated a bit by the fact that CompositeBuilder is a proxy, not a subclass of BuilderBase. """ return (isinstance(obj, BuilderBase) or isinstance(obj, CompositeBuilder) or callable(obj))
# Local Variables: # tab-width:4 # indent-tabs-mode:nil # End: # vim: set expandtab tabstop=4 shiftwidth=4: