Source code for SCons.Taskmaster

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"""Generic Taskmaster module for the SCons build engine.

This module contains the primary interface(s) between a wrapping user
interface and the SCons build engine.  There are two key classes here:

    This is the main engine for walking the dependency graph and
    calling things to decide what does or doesn't need to be built.

    This is the base class for allowing a wrapping interface to
    decide what does or doesn't actually need to be done.  The
    intention is for a wrapping interface to subclass this as
    appropriate for different types of behavior it may need.

    The canonical example is the SCons native Python interface,
    which has Task subclasses that handle its specific behavior,
    like printing "'foo' is up to date" when a top-level target
    doesn't need to be built, and handling the -c option by removing
    targets as its "build" action.  There is also a separate subclass
    for suppressing this output when the -q option is used.

    The Taskmaster instantiates a Task object for each (set of)
    target(s) that it decides need to be evaluated and/or built.
import io
import sys
from abc import ABC, abstractmethod
from itertools import chain
import logging

import SCons.Errors
import SCons.Node
import SCons.Warnings
from SCons.Util import DispatchingFormatter

StateString = SCons.Node.StateString
NODE_NO_STATE = SCons.Node.no_state
NODE_PENDING = SCons.Node.pending
NODE_EXECUTING = SCons.Node.executing
NODE_UP_TO_DATE = SCons.Node.up_to_date
NODE_EXECUTED = SCons.Node.executed
NODE_FAILED = SCons.Node.failed
print_prepare = False               # set by option --debug=prepare

# A subsystem for recording stats about how different Nodes are handled by
# the main Taskmaster loop.  There's no external control here (no need for
# a --debug= option); enable it by changing the value of CollectStats.

CollectStats = None

[docs]class Stats: """ A simple class for holding statistics about the disposition of a Node by the Taskmaster. If we're collecting statistics, each Node processed by the Taskmaster gets one of these attached, in which case the Taskmaster records its decision each time it processes the Node. (Ideally, that's just once per Node.) """ def __init__(self) -> None: """ Instantiates a Taskmaster.Stats object, initializing all appropriate counters to zero. """ self.considered = 0 self.already_handled = 0 self.problem = 0 self.child_failed = 0 self.not_built = 0 self.side_effects = 0 = 0
StatsNodes = [] fmt = "%(considered)3d "\ "%(already_handled)3d " \ "%(problem)3d " \ "%(child_failed)3d " \ "%(not_built)3d " \ "%(side_effects)3d " \ "%(build)3d "
[docs]def dump_stats() -> None: for n in sorted(StatsNodes, key=lambda a: str(a)): print((fmt % n.attributes.stats.__dict__) + str(n))
[docs]class Task(ABC): """ SCons build engine abstract task class. This controls the interaction of the actual building of node and the rest of the engine. This is expected to handle all of the normally-customizable aspects of controlling a build, so any given application *should* be able to do what it wants by sub-classing this class and overriding methods as appropriate. If an application needs to customize something by sub-classing Taskmaster (or some other build engine class), we should first try to migrate that functionality into this class. Note that it's generally a good idea for sub-classes to call these methods explicitly to update state, etc., rather than roll their own interaction with Taskmaster from scratch. """ LOGGER = None def __init__(self, tm, targets, top, node) -> None: = tm self.targets = targets = top self.node = node self.exc_clear()
[docs] def trace_message(self, node, description: str='node') -> None: # This grabs the name of the function which calls trace_message() method_name=sys._getframe(1).f_code.co_name+"():" Task.LOGGER.debug('%-15s %s %s' % (method_name, description,
[docs] def display(self, message) -> None: """ Hook to allow the calling interface to display a message. This hook gets called as part of preparing a task for execution (that is, a Node to be built). As part of figuring out what Node should be built next, the actual target list may be altered, along with a message describing the alteration. The calling interface can subclass Task and provide a concrete implementation of this method to see those messages. """ pass
[docs] def prepare(self) -> None: """ Called just before the task is executed. This is mainly intended to give the target Nodes a chance to unlink underlying files and make all necessary directories before the Action is actually called to build the targets. """ global print_prepare T = if T: self.trace_message(self.node) # Now that it's the appropriate time, give the TaskMaster a # chance to raise any exceptions it encountered while preparing # this task. self.exception_raise() if self.display( = None # Let the targets take care of any necessary preparations. # This includes verifying that all of the necessary sources # and dependencies exist, removing the target file(s), etc. # # As of April 2008, the get_executor().prepare() method makes # sure that all of the aggregate sources necessary to build this # Task's target(s) exist in one up-front check. The individual # target t.prepare() methods check that each target's explicit # or implicit dependencies exists, and also initialize the # .sconsign info. executor = self.targets[0].get_executor() if executor is None: return executor.prepare() for t in executor.get_action_targets(): if print_prepare: print("Preparing target %s..."%t) for s in t.side_effects: print("...with side-effect %s..."%s) t.prepare() for s in t.side_effects: if print_prepare: print("...Preparing side-effect %s..."%s) s.prepare()
[docs] def get_target(self): """Fetch the target being built or updated by this task. """ return self.node
[docs] @abstractmethod def needs_execute(self): return
[docs] def execute(self): """ Called to execute the task. This method is called from multiple threads in a parallel build, so only do thread safe stuff here. Do thread unsafe stuff in prepare(), executed() or failed(). """ T = if T: self.trace_message(self.node) try: cached_targets = [] for t in self.targets: if not t.retrieve_from_cache(): break cached_targets.append(t) if len(cached_targets) < len(self.targets): # Remove targets before building. It's possible that we # partially retrieved targets from the cache, leaving # them in read-only mode. That might cause the command # to fail. # for t in cached_targets: try: t.fs.unlink(t.get_internal_path()) except OSError as e: SCons.Warnings.warn(SCons.Warnings.CacheCleanupErrorWarning, "Failed copying all target files from cache, Error while attempting to remove file %s retrieved from cache: %s" % (t.get_internal_path(), e)) self.targets[0].build() for t in self.targets: t.push_to_cache() else: for t in cached_targets: t.cached = 1 except SystemExit: exc_value = sys.exc_info()[1] raise SCons.Errors.ExplicitExit(self.targets[0], exc_value.code) except SCons.Errors.UserError: raise except SCons.Errors.BuildError: raise except Exception as e: buildError = SCons.Errors.convert_to_BuildError(e) buildError.node = self.targets[0] buildError.exc_info = sys.exc_info() raise buildError
[docs] def executed_without_callbacks(self) -> None: """ Called when the task has been successfully executed and the Taskmaster instance doesn't want to call the Node's callback methods. """ T = if T: self.trace_message(self.node) for t in self.targets: if t.get_state() == NODE_EXECUTING: for side_effect in t.side_effects: side_effect.set_state(NODE_NO_STATE) t.set_state(NODE_EXECUTED)
[docs] def executed_with_callbacks(self) -> None: """ Called when the task has been successfully executed and the Taskmaster instance wants to call the Node's callback methods. This may have been a do-nothing operation (to preserve build order), so we must check the node's state before deciding whether it was "built", in which case we call the appropriate Node method. In any event, we always call "visited()", which will handle any post-visit actions that must take place regardless of whether or not the target was an actual built target or a source Node. """ global print_prepare T = if T: self.trace_message(self.node) for t in self.targets: if t.get_state() == NODE_EXECUTING: for side_effect in t.side_effects: side_effect.set_state(NODE_NO_STATE) t.set_state(NODE_EXECUTED) t.built() t.visited() if (not print_prepare and (not hasattr(self, 'options') or not self.options.debug_includes)): t.release_target_info() else: t.visited()
executed = executed_with_callbacks
[docs] def failed(self) -> None: """ Default action when a task fails: stop the build. Note: Although this function is normally invoked on nodes in the executing state, it might also be invoked on up-to-date nodes when using Configure(). """ self.fail_stop()
[docs] def fail_stop(self) -> None: """ Explicit stop-the-build failure. This sets failure status on the target nodes and all of their dependent parent nodes. Note: Although this function is normally invoked on nodes in the executing state, it might also be invoked on up-to-date nodes when using Configure(). """ T = if T: self.trace_message(self.node) # Invoke will_not_build() to clean-up the pending children # list., lambda n: n.set_state(NODE_FAILED)) # Tell the taskmaster to not start any new tasks # We're stopping because of a build failure, but give the # calling Task class a chance to postprocess() the top-level # target under which the build failure occurred. self.targets = [] = 1
[docs] def fail_continue(self) -> None: """ Explicit continue-the-build failure. This sets failure status on the target nodes and all of their dependent parent nodes. Note: Although this function is normally invoked on nodes in the executing state, it might also be invoked on up-to-date nodes when using Configure(). """ T = if T: self.trace_message(self.node), lambda n: n.set_state(NODE_FAILED))
[docs] def make_ready_all(self) -> None: """ Marks all targets in a task ready for execution. This is used when the interface needs every target Node to be visited--the canonical example being the "scons -c" option. """ T = if T: self.trace_message(self.node) self.out_of_date = self.targets[:] for t in self.targets: t.disambiguate().set_state(NODE_EXECUTING) for s in t.side_effects: # add disambiguate here to mirror the call on targets above s.disambiguate().set_state(NODE_EXECUTING)
[docs] def make_ready_current(self): """ Marks all targets in a task ready for execution if any target is not current. This is the default behavior for building only what's necessary. """ global print_prepare T = if T:'\n') # Prefix message with new line. This is a hack self.trace_message(self.node) self.out_of_date = [] needs_executing = False for t in self.targets: try: t.disambiguate().make_ready() is_up_to_date = not t.has_builder() or \ (not t.always_build and t.is_up_to_date()) except OSError as e: raise SCons.Errors.BuildError(node=t, errstr=e.strerror, filename=e.filename) if not is_up_to_date: self.out_of_date.append(t) needs_executing = True if needs_executing: for t in self.targets: t.set_state(NODE_EXECUTING) for s in t.side_effects: # add disambiguate here to mirror the call on targets in first loop above s.disambiguate().set_state(NODE_EXECUTING) else: for t in self.targets: # We must invoke visited() to ensure that the node # information has been computed before allowing the # parent nodes to execute. (That could occur in a # parallel build...) t.visited() t.set_state(NODE_UP_TO_DATE) if (not print_prepare and (not hasattr(self, 'options') or not self.options.debug_includes)): t.release_target_info()
make_ready = make_ready_current
[docs] def postprocess(self) -> None: """ Post-processes a task after it's been executed. This examines all the targets just built (or not, we don't care if the build was successful, or even if there was no build because everything was up-to-date) to see if they have any waiting parent Nodes, or Nodes waiting on a common side effect, that can be put back on the candidates list. """ T = if T: self.trace_message(self.node) # We may have built multiple targets, some of which may have # common parents waiting for this build. Count up how many # targets each parent was waiting for so we can subtract the # values later, and so we *don't* put waiting side-effect Nodes # back on the candidates list if the Node is also a waiting # parent. targets = set(self.targets) pending_children = parents = {} for t in targets: # A node can only be in the pending_children set if it has # some waiting_parents. if t.waiting_parents: if T: self.trace_message(t, 'removing') pending_children.discard(t) for p in t.waiting_parents: parents[p] = parents.get(p, 0) + 1 t.waiting_parents = set() for t in targets: if t.side_effects is not None: for s in t.side_effects: if s.get_state() == NODE_EXECUTING: s.set_state(NODE_NO_STATE) # The side-effects may have been transferred to # NODE_NO_STATE by executed_with{,out}_callbacks, but was # not taken out of the waiting parents/pending children # data structures. Check for that now. if s.get_state() == NODE_NO_STATE and s.waiting_parents: pending_children.discard(s) for p in s.waiting_parents: parents[p] = parents.get(p, 0) + 1 s.waiting_parents = set() for p in s.waiting_s_e: if p.ref_count == 0: for p, subtract in parents.items(): p.ref_count = p.ref_count - subtract if T: self.trace_message(p, 'adjusted parent ref count') if p.ref_count == 0: for t in targets: t.postprocess()
# Exception handling subsystem. # # Exceptions that occur while walking the DAG or examining Nodes # must be raised, but must be raised at an appropriate time and in # a controlled manner so we can, if necessary, recover gracefully, # possibly write out signature information for Nodes we've updated, # etc. This is done by having the Taskmaster tell us about the # exception, and letting
[docs] def exc_info(self): """ Returns info about a recorded exception. """ return self.exception
[docs] def exc_clear(self) -> None: """ Clears any recorded exception. This also changes the "exception_raise" attribute to point to the appropriate do-nothing method. """ self.exception = (None, None, None) self.exception_raise = self._no_exception_to_raise
[docs] def exception_set(self, exception=None) -> None: """ Records an exception to be raised at the appropriate time. This also changes the "exception_raise" attribute to point to the method that will, in fact """ if not exception: exception = sys.exc_info() self.exception = exception self.exception_raise = self._exception_raise
[docs] def _no_exception_to_raise(self) -> None: pass
[docs] def _exception_raise(self): """ Raises a pending exception that was recorded while getting a Task ready for execution. """ exc = self.exc_info()[:] try: exc_type, exc_value, exc_traceback = exc except ValueError: exc_type, exc_value = exc # pylint: disable=unbalanced-tuple-unpacking exc_traceback = None # raise exc_type(exc_value).with_traceback(exc_traceback) if isinstance(exc_value, Exception): #hasattr(exc_value, 'with_traceback'): # If exc_value is an exception, then just reraise raise exc_value.with_traceback(exc_traceback) else: # else we'll create an exception using the value and raise that raise exc_type(exc_value).with_traceback(exc_traceback)
# raise e.__class__, e.__class__(e), sys.exc_info()[2] # exec("raise exc_type(exc_value).with_traceback(exc_traceback)")
[docs]class AlwaysTask(Task):
[docs] def needs_execute(self) -> bool: """ Always returns True (indicating this Task should always be executed). Subclasses that need this behavior (as opposed to the default of only executing Nodes that are out of date w.r.t. their dependencies) can use this as follows: class MyTaskSubclass(SCons.Taskmaster.Task): needs_execute = SCons.Taskmaster.AlwaysTask.needs_execute """ return True
[docs]class OutOfDateTask(Task):
[docs] def needs_execute(self): """ Returns True (indicating this Task should be executed) if this Task's target state indicates it needs executing, which has already been determined by an earlier up-to-date check. """ return self.targets[0].get_state() == SCons.Node.executing
[docs]def find_cycle(stack, visited): if stack[-1] in visited: return None visited.add(stack[-1]) for n in stack[-1].waiting_parents: stack.append(n) if stack[0] == stack[-1]: return stack if find_cycle(stack, visited): return stack stack.pop() return None
[docs]class Taskmaster: """ The Taskmaster for walking the dependency DAG. """ def __init__(self, targets=[], tasker=None, order=None, trace=None) -> None: self.original_top = targets self.top_targets_left = targets[:] self.top_targets_left.reverse() self.candidates = [] if tasker is None: tasker = OutOfDateTask self.tasker = tasker if not order: order = lambda l: l self.order = order self.message = None self.next_candidate = self.find_next_candidate self.pending_children = set() self.trace = False self.configure_trace(trace)
[docs] def configure_trace(self, trace=None) -> None: """ This handles the command line option --taskmastertrace= It can be: - : output to stdout <filename> : output to a file False/None : Do not trace """ if not trace: self.trace = False return # TODO: May want to switch format to something like this. # log_format = ( # '%(relativeCreated)05dms' # ':%(relfilename)s' # ':%(funcName)s' # '#%(lineno)s' # ': %(message)s' # ) tm_formatter = logging.Formatter('Taskmaster: %(message)s') if isinstance(trace, io.StringIO): log_handler = logging.StreamHandler(trace) elif trace == '-': log_handler = logging.StreamHandler(sys.stdout) elif trace: log_handler = logging.FileHandler(filename=trace) logger = logging.getLogger('Taskmaster') logger.setLevel(level=logging.DEBUG) logger.addHandler(log_handler) self.trace = logger logger.log_handler = log_handler # Now setup Task's logger. tl = logging.getLogger("Task") tl.setLevel(level=logging.DEBUG) tl.addHandler(log_handler) task_formatter = logging.Formatter('%(name)s.%(message)s') Task.LOGGER = tl self.trace.log_handler = log_handler log_handler.setFormatter(DispatchingFormatter( formatters={ 'Taskmaster': tm_formatter, 'Task': task_formatter, 'Job': task_formatter, }, default_formatter=logging.Formatter('%(message)s') ))
[docs] def find_next_candidate(self): """ Returns the next candidate Node for (potential) evaluation. The candidate list (really a stack) initially consists of all of the top-level (command line) targets provided when the Taskmaster was initialized. While we walk the DAG, visiting Nodes, all the children that haven't finished processing get pushed on to the candidate list. Each child can then be popped and examined in turn for whether *their* children are all up-to-date, in which case a Task will be created for their actual evaluation and potential building. Here is where we also allow candidate Nodes to alter the list of Nodes that should be examined. This is used, for example, when invoking SCons in a source directory. A source directory Node can return its corresponding build directory Node, essentially saying, "Hey, you really need to build this thing over here instead." """ try: return self.candidates.pop() except IndexError: pass try: node = self.top_targets_left.pop() except IndexError: return None self.current_top = node alt, message = node.alter_targets() if alt: self.message = message self.candidates.append(node) self.candidates.extend(self.order(alt)) node = self.candidates.pop() return node
[docs] def no_next_candidate(self): """ Stops Taskmaster processing by not returning a next candidate. Note that we have to clean-up the Taskmaster candidate list because the cycle detection depends on the fact all nodes have been processed somehow. """ while self.candidates: candidates = self.candidates self.candidates = [] self.will_not_build(candidates) return None
[docs] def _validate_pending_children(self) -> None: """ Validate the content of the pending_children set. Assert if an internal error is found. This function is used strictly for debugging the taskmaster by checking that no invariants are violated. It is not used in normal operation. The pending_children set is used to detect cycles in the dependency graph. We call a "pending child" a child that is found in the "pending" state when checking the dependencies of its parent node. A pending child can occur when the Taskmaster completes a loop through a cycle. For example, let's imagine a graph made of three nodes (A, B and C) making a cycle. The evaluation starts at node A. The Taskmaster first considers whether node A's child B is up-to-date. Then, recursively, node B needs to check whether node C is up-to-date. This leaves us with a dependency graph looking like:: Next candidate \ \ Node A (Pending) --> Node B(Pending) --> Node C (NoState) ^ | | | +-------------------------------------+ Now, when the Taskmaster examines the Node C's child Node A, it finds that Node A is in the "pending" state. Therefore, Node A is a pending child of node C. Pending children indicate that the Taskmaster has potentially loop back through a cycle. We say potentially because it could also occur when a DAG is evaluated in parallel. For example, consider the following graph:: Node A (Pending) --> Node B(Pending) --> Node C (Pending) --> ... | ^ | | +----------> Node D (NoState) --------+ / Next candidate / The Taskmaster first evaluates the nodes A, B, and C and starts building some children of node C. Assuming, that the maximum parallel level has not been reached, the Taskmaster will examine Node D. It will find that Node C is a pending child of Node D. In summary, evaluating a graph with a cycle will always involve a pending child at one point. A pending child might indicate either a cycle or a diamond-shaped DAG. Only a fraction of the nodes ends-up being a "pending child" of another node. This keeps the pending_children set small in practice. We can differentiate between the two cases if we wait until the end of the build. At this point, all the pending children nodes due to a diamond-shaped DAG will have been properly built (or will have failed to build). But, the pending children involved in a cycle will still be in the pending state. The taskmaster removes nodes from the pending_children set as soon as a pending_children node moves out of the pending state. This also helps to keep the pending_children set small. """ for n in self.pending_children: assert n.state in (NODE_PENDING, NODE_EXECUTING), \ (str(n), StateString[n.state]) assert len(n.waiting_parents) != 0, (str(n), len(n.waiting_parents)) for p in n.waiting_parents: assert p.ref_count > 0, (str(n), str(p), p.ref_count)
[docs] def tm_trace_node(self, node) -> str: return('<%-10s %-3s %s>' % (StateString[node.get_state()], node.ref_count, repr(str(node))))
[docs] def _find_next_ready_node(self): """ Finds the next node that is ready to be built. This is *the* main guts of the DAG walk. We loop through the list of candidates, looking for something that has no un-built children (i.e., that is a leaf Node or has dependencies that are all leaf Nodes or up-to-date). Candidate Nodes are re-scanned (both the target Node itself and its sources, which are always scanned in the context of a given target) to discover implicit dependencies. A Node that must wait for some children to be built will be put back on the candidates list after the children have finished building. A Node that has been put back on the candidates list in this way may have itself (or its sources) re-scanned, in order to handle generated header files (e.g.) and the implicit dependencies therein. Note that this method does not do any signature calculation or up-to-date check itself. All of that is handled by the Task class. This is purely concerned with the dependency graph walk. """ self.ready_exc = None T = self.trace if T:'\n') # Prefix message with new line. This is a hack self.trace.debug('Looking for a node to evaluate') while True: node = self.next_candidate() if node is None: if T: self.trace.debug('No candidate anymore.') return None node = node.disambiguate() state = node.get_state() # For debugging only: # # try: # self._validate_pending_children() # except: # self.ready_exc = sys.exc_info() # return node if CollectStats: if not hasattr(node.attributes, 'stats'): node.attributes.stats = Stats() StatsNodes.append(node) S = node.attributes.stats S.considered = S.considered + 1 else: S = None if T: self.trace.debug(' Considering node %s and its children:' % self.tm_trace_node(node)) if state == NODE_NO_STATE: # Mark this node as being on the execution stack: node.set_state(NODE_PENDING) elif state > NODE_PENDING: # Skip this node if it has already been evaluated: if S: S.already_handled = S.already_handled + 1 if T: self.trace.debug(' already handled (executed)') continue executor = node.get_executor() try: children = executor.get_all_children() except SystemExit: exc_value = sys.exc_info()[1] e = SCons.Errors.ExplicitExit(node, exc_value.code) self.ready_exc = (SCons.Errors.ExplicitExit, e) if T: self.trace.debug(' SystemExit') return node except Exception as e: # We had a problem just trying to figure out the # children (like a child couldn't be linked in to a # VariantDir, or a Scanner threw something). Arrange to # raise the exception when the Task is "executed." self.ready_exc = sys.exc_info() if S: S.problem = S.problem + 1 if T: self.trace.debug(' exception %s while scanning children.' % e) return node children_not_visited = [] children_pending = set() children_not_ready = [] children_failed = False for child in chain(executor.get_all_prerequisites(), children): childstate = child.get_state() if T: self.trace.debug(' ' + self.tm_trace_node(child)) if childstate == NODE_NO_STATE: children_not_visited.append(child) elif childstate == NODE_PENDING: children_pending.add(child) elif childstate == NODE_FAILED: children_failed = True if childstate <= NODE_EXECUTING: children_not_ready.append(child) # These nodes have not even been visited yet. Add # them to the list so that on some next pass we can # take a stab at evaluating them (or their children). if children_not_visited: if len(children_not_visited) > 1: children_not_visited.reverse() self.candidates.extend(self.order(children_not_visited)) # if T and children_not_visited: # self.trace.debug(' adding to candidates: %s' % map(str, children_not_visited)) # self.trace.debug(' candidates now: %s\n' % map(str, self.candidates)) # Skip this node if any of its children have failed. # # This catches the case where we're descending a top-level # target and one of our children failed while trying to be # built by a *previous* descent of an earlier top-level # target. # # It can also occur if a node is reused in multiple # targets. One first descends though the one of the # target, the next time occurs through the other target. # # Note that we can only have failed_children if the # --keep-going flag was used, because without it the build # will stop before diving in the other branch. # # Note that even if one of the children fails, we still # added the other children to the list of candidate nodes # to keep on building (--keep-going). if children_failed: for n in executor.get_action_targets(): n.set_state(NODE_FAILED) if S: S.child_failed = S.child_failed + 1 if T: self.trace.debug('****** %s' % self.tm_trace_node(node)) continue if children_not_ready: for child in children_not_ready: # We're waiting on one or more derived targets # that have not yet finished building. if S: S.not_built = S.not_built + 1 # Add this node to the waiting parents lists of # anything we're waiting on, with a reference # count so we can be put back on the list for # re-evaluation when they've all finished. node.ref_count = node.ref_count + child.add_to_waiting_parents(node) if T: self.trace.debug(' adjusted ref count: %s, child %s' % (self.tm_trace_node(node), repr(str(child)))) if T: for pc in children_pending: self.trace.debug(' adding %s to the pending children set' % self.tm_trace_node(pc)) self.pending_children = self.pending_children | children_pending continue # Skip this node if it has side-effects that are # currently being built: wait_side_effects = False for se in executor.get_action_side_effects(): if se.get_state() == NODE_EXECUTING: se.add_to_waiting_s_e(node) wait_side_effects = True if wait_side_effects: if S: S.side_effects = S.side_effects + 1 continue # The default when we've gotten through all of the checks above: # this node is ready to be built. if S: = + 1 if T: self.trace.debug('Evaluating %s' % self.tm_trace_node(node)) # For debugging only: # # try: # self._validate_pending_children() # except: # self.ready_exc = sys.exc_info() # return node return node return None
[docs] def next_task(self): """ Returns the next task to be executed. This simply asks for the next Node to be evaluated, and then wraps it in the specific Task subclass with which we were initialized. """ node = self._find_next_ready_node() if node is None: return None executor = node.get_executor() if executor is None: return None tlist = executor.get_all_targets() task = self.tasker(self, tlist, node in self.original_top, node) try: task.make_ready() except Exception as e : # We had a problem just trying to get this task ready (like # a child couldn't be linked to a VariantDir when deciding # whether this node is current). Arrange to raise the # exception when the Task is "executed." self.ready_exc = sys.exc_info() if self.ready_exc: task.exception_set(self.ready_exc) self.ready_exc = None return task
[docs] def will_not_build(self, nodes, node_func=lambda n: None) -> None: """ Perform clean-up about nodes that will never be built. Invokes a user defined function on all of these nodes (including all of their parents). """ T = self.trace pending_children = self.pending_children to_visit = set(nodes) pending_children = pending_children - to_visit if T: for n in nodes: self.trace.debug(' removing node %s from the pending children set\n' % self.tm_trace_node(n)) try: while len(to_visit): node = to_visit.pop() node_func(node) # Prune recursion by flushing the waiting children # list immediately. parents = node.waiting_parents node.waiting_parents = set() to_visit = to_visit | parents pending_children = pending_children - parents for p in parents: p.ref_count = p.ref_count - 1 if T: self.trace.debug(' removing parent %s from the pending children set\n' % self.tm_trace_node(p)) except KeyError: # The container to_visit has been emptied. pass # We have the stick back the pending_children list into the # taskmaster because the python 1.5.2 compatibility does not # allow us to use in-place updates self.pending_children = pending_children
[docs] def stop(self) -> None: """ Stops the current build completely. """ self.next_candidate = self.no_next_candidate
[docs] def cleanup(self): """ Check for dependency cycles. """ if not self.pending_children: return nclist = [(n, find_cycle([n], set())) for n in self.pending_children] genuine_cycles = [ node for node,cycle in nclist if cycle or node.get_state() != NODE_EXECUTED ] if not genuine_cycles: # All of the "cycles" found were single nodes in EXECUTED state, # which is to say, they really weren't cycles. Just return. return desc = 'Found dependency cycle(s):\n' for node, cycle in nclist: if cycle: desc = desc + " " + " -> ".join(map(str, cycle)) + "\n" else: desc = desc + \ " Internal Error: no cycle found for node %s (%s) in state %s\n" % \ (node, repr(node), StateString[node.get_state()]) raise SCons.Errors.UserError(desc)
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