Really handle lack of the threading.py module when run by non-threaded Pythons.

5 files changed, 158 insertions, 109 deletions

diff --git a/src/CHANGES.txt b/src/CHANGES.txt
index bb32ad8..d7a4aec 100644
--- a/src/CHANGES.txt
+++ b/src/CHANGES.txt
@@ -132,6 +132,9 @@ RELEASE X.XX - XXX
     the one being checked for.  (Prototype code contributed by Gerard
     Patel and Niall Douglas).
 
+  - Supply a warning when -j is used and threading isn't built in to
+    the current version of Python.
+
   From Clark McGrew:
 
   - Generalize the action for .tex files so that it will decide whether
diff --git a/src/engine/SCons/Job.py b/src/engine/SCons/Job.py
index d26b73c..ee84e34 100644
--- a/src/engine/SCons/Job.py
+++ b/src/engine/SCons/Job.py
@@ -43,12 +43,23 @@ class Jobs:
         If 'num' is 1 or less, then a serial job will be used,
         otherwise a parallel job with 'num' worker threads will
         be used.
+
+        The 'num_jobs' attribute will be set to the actual number of jobs
+        allocated.  If more than one job is requested but the Parallel
+        class can't do it, it gets reset to 1.  Wrapping interfaces that
+        care should check the value of 'num_jobs' after initialization.
         """
 
+        self.job = None
         if num > 1:
-            self.job = Parallel(taskmaster, num)
-        else:
+            try:
+                self.job = Parallel(taskmaster, num)
+                self.num_jobs = num
+            except NameError:
+                pass
+        if self.job is None:
             self.job = Serial(taskmaster)
+            self.num_jobs = 1
 
     def run(self):
         """run the job"""
@@ -116,127 +127,127 @@ try:
     import threading
 except ImportError:
     pass
+else:
+    class Worker(threading.Thread):
+        """A worker thread waits on a task to be posted to its request queue,
+        dequeues the task, executes it, and posts a tuple including the task
+        and a boolean indicating whether the task executed successfully. """
+
+        def __init__(self, requestQueue, resultsQueue):
+            threading.Thread.__init__(self)
+            self.setDaemon(1)
+            self.requestQueue = requestQueue
+            self.resultsQueue = resultsQueue
+            self.start()
+
+        def run(self):
+            while 1:
+                task = self.requestQueue.get()
 
-class Worker(threading.Thread):
-    """A worker thread waits on a task to be posted to its request queue,
-    dequeues the task, executes it, and posts a tuple including the task
-    and a boolean indicating whether the task executed successfully. """
-
-    def __init__(self, requestQueue, resultsQueue):
-        threading.Thread.__init__(self)
-        self.setDaemon(1)
-        self.requestQueue = requestQueue
-        self.resultsQueue = resultsQueue
-        self.start()
-
-    def run(self):
-        while 1:
-            task = self.requestQueue.get()
-
-            try:
-                task.execute()
-            except KeyboardInterrupt:
-                # be explicit here for test/interrupts.py
-                ok = False
-            except:
-                ok = 0
-            else:
-                ok = 1
-
-            self.resultsQueue.put((task, ok))
-
-class ThreadPool:
-    """This class is responsible for spawning and managing worker threads."""
+                try:
+                    task.execute()
+                except KeyboardInterrupt:
+                    # be explicit here for test/interrupts.py
+                    ok = False
+                except:
+                    ok = 0
+                else:
+                    ok = 1
 
-    def __init__(self, num):
-        """Create the request and reply queues, and 'num' worker threads."""
-        self.requestQueue = Queue.Queue(0)
-        self.resultsQueue = Queue.Queue(0)
+                self.resultsQueue.put((task, ok))
 
-        # Create worker threads
-        for i in range(num):
-            worker = Worker(self.requestQueue, self.resultsQueue)
+    class ThreadPool:
+        """This class is responsible for spawning and managing worker threads."""
 
-    def put(self, obj):
-        """Put task into request queue."""
-        self.requestQueue.put(obj)
+        def __init__(self, num):
+            """Create the request and reply queues, and 'num' worker threads."""
+            self.requestQueue = Queue.Queue(0)
+            self.resultsQueue = Queue.Queue(0)
 
-    def get(self, block = 1):
-        """Remove and return a result tuple from the results queue."""
-        return self.resultsQueue.get(block)
-        
-    def get_nowait(self):
-        """Remove and result a result tuple from the results queue 
-        without blocking."""
-        return self.get(0)
+            # Create worker threads
+            for i in range(num):
+                worker = Worker(self.requestQueue, self.resultsQueue)
 
-class Parallel:
-    """This class is used to execute tasks in parallel, and is somewhat 
-    less efficient than Serial, but is appropriate for parallel builds.
+        def put(self, obj):
+            """Put task into request queue."""
+            self.requestQueue.put(obj)
 
-    This class is thread safe.
-    """
+        def get(self, block = 1):
+            """Remove and return a result tuple from the results queue."""
+            return self.resultsQueue.get(block)
+            
+        def get_nowait(self):
+            """Remove and result a result tuple from the results queue 
+            without blocking."""
+            return self.get(0)
 
-    def __init__(self, taskmaster, num):
-        """Create a new parallel job given a taskmaster.
+    class Parallel:
+        """This class is used to execute tasks in parallel, and is somewhat 
+        less efficient than Serial, but is appropriate for parallel builds.
 
-        The taskmaster's next_task() method should return the next task
-        that needs to be executed, or None if there are no more tasks. The
-        taskmaster's executed() method will be called for each task when it
-        is successfully executed or failed() will be called if the task
-        failed to execute (i.e. execute() raised an exception).  The
-        taskmaster's is_blocked() method should return true iff there are
-        more tasks, but they can't be executed until one or more other
-        tasks have been executed. next_task() will be called iff
-        is_blocked() returned false.
-
-        Note: calls to taskmaster are serialized, but calls to execute() on
-        distinct tasks are not serialized, because that is the whole point
-        of parallel jobs: they can execute multiple tasks
-        simultaneously. """
+        This class is thread safe.
+        """
 
-        self.taskmaster = taskmaster
-        self.tp = ThreadPool(num)
+        def __init__(self, taskmaster, num):
+            """Create a new parallel job given a taskmaster.
 
-        self.jobs = 0
-        self.maxjobs = num
+            The taskmaster's next_task() method should return the next task
+            that needs to be executed, or None if there are no more tasks. The
+            taskmaster's executed() method will be called for each task when it
+            is successfully executed or failed() will be called if the task
+            failed to execute (i.e. execute() raised an exception).  The
+            taskmaster's is_blocked() method should return true iff there are
+            more tasks, but they can't be executed until one or more other
+            tasks have been executed. next_task() will be called iff
+            is_blocked() returned false.
 
-    def start(self):
-        """Start the job. This will begin pulling tasks from the
-        taskmaster and executing them, and return when there are no
-        more tasks. If a task fails to execute (i.e. execute() raises
-        an exception), then the job will stop."""
+            Note: calls to taskmaster are serialized, but calls to execute() on
+            distinct tasks are not serialized, because that is the whole point
+            of parallel jobs: they can execute multiple tasks
+            simultaneously. """
 
-        while 1:
-            if self.jobs < self.maxjobs:
-                task = self.taskmaster.next_task()
-                if task is None:
-                    break
+            self.taskmaster = taskmaster
+            self.tp = ThreadPool(num)
 
-                # prepare task for execution
-                try:
-                    task.prepare()
-                except KeyboardInterrupt:
-                    raise
-                except:
-                    # Let the failed() callback function arrange for the
-                    # build to stop if that's appropriate.
-                    task.failed()
+            self.jobs = 0
+            self.maxjobs = num
 
-                # dispatch task
-                self.tp.put(task)
-                self.jobs = self.jobs + 1
+        def start(self):
+            """Start the job. This will begin pulling tasks from the
+            taskmaster and executing them, and return when there are no
+            more tasks. If a task fails to execute (i.e. execute() raises
+            an exception), then the job will stop."""
 
             while 1:
-                try:
-                    task, ok = self.tp.get_nowait()
-                except Queue.Empty:
-                    if not (self.jobs is self.maxjobs or self.taskmaster.is_blocked()):
+                if self.jobs < self.maxjobs:
+                    task = self.taskmaster.next_task()
+                    if task is None:
                         break
-                    task, ok = self.tp.get()
 
-                self.jobs = self.jobs - 1
-                if ok:
-                    task.executed()
-                else:
-                    task.failed()
+                    # prepare task for execution
+                    try:
+                        task.prepare()
+                    except KeyboardInterrupt:
+                        raise
+                    except:
+                        # Let the failed() callback function arrange for the
+                        # build to stop if that's appropriate.
+                        task.failed()
+
+                    # dispatch task
+                    self.tp.put(task)
+                    self.jobs = self.jobs + 1
+
+                while 1:
+                    try:
+                        task, ok = self.tp.get_nowait()
+                    except Queue.Empty:
+                        if not (self.jobs is self.maxjobs or self.taskmaster.is_blocked()):
+                            break
+                        task, ok = self.tp.get()
+
+                    self.jobs = self.jobs - 1
+                    if ok:
+                        task.executed()
+                    else:
+                        task.failed()
diff --git a/src/engine/SCons/JobTests.py b/src/engine/SCons/JobTests.py
index 1b09fd6..1b0128b 100644
--- a/src/engine/SCons/JobTests.py
+++ b/src/engine/SCons/JobTests.py
@@ -190,7 +190,7 @@ class Taskmaster:
 class ParallelTestCase(unittest.TestCase):
     def runTest(self):
         "test parallel jobs"
-        
+
         try:
             import threading
         except:
@@ -226,6 +226,31 @@ class SerialTestCase(unittest.TestCase):
         self.failIf(taskmaster.num_failed,
                     "some task(s) failed to execute") 
 
+class NoParallelTestCase(unittest.TestCase):
+    def runTest(self):
+        "test handling lack of parallel support"
+        def NoParallel(tm, num):
+            raise NameError
+        save_Parallel = SCons.Job.Parallel
+        SCons.Job.Parallel = NoParallel
+        try:
+            taskmaster = Taskmaster(num_tasks, self, Task)
+            jobs = SCons.Job.Jobs(2, taskmaster)
+            self.failUnless(jobs.num_jobs == 1, 
+                            "unexpected number of jobs %d" % jobs.num_jobs)
+            jobs.run()
+            self.failUnless(taskmaster.tasks_were_serial(),
+                            "the tasks were not executed in series")
+            self.failUnless(taskmaster.all_tasks_are_executed(),
+                            "all the tests were not executed")
+            self.failUnless(taskmaster.all_tasks_are_iterated(),
+                            "all the tests were not iterated over")
+            self.failIf(taskmaster.num_failed,
+                        "some task(s) failed to execute") 
+        finally:
+            SCons.Job.Parallel = save_Parallel
+
+
 class SerialExceptionTestCase(unittest.TestCase):
     def runTest(self):
         "test a serial job with tasks that raise exceptions"
@@ -261,6 +286,7 @@ def suite():
     suite = unittest.TestSuite()
     suite.addTest(ParallelTestCase())
     suite.addTest(SerialTestCase())
+    suite.addTest(NoParallelTestCase())
     suite.addTest(SerialExceptionTestCase())
     suite.addTest(ParallelExceptionTestCase())
     return suite
diff --git a/src/engine/SCons/Script/__init__.py b/src/engine/SCons/Script/__init__.py
index 03cb6d8..a533c29 100644
--- a/src/engine/SCons/Script/__init__.py
+++ b/src/engine/SCons/Script/__init__.py
@@ -703,6 +703,7 @@ def _main(args, parser):
     SCons.Warnings._warningOut = _scons_internal_warning
     SCons.Warnings.enableWarningClass(SCons.Warnings.DeprecatedWarning)
     SCons.Warnings.enableWarningClass(SCons.Warnings.CorruptSConsignWarning)
+    SCons.Warnings.enableWarningClass(SCons.Warnings.NoParallelSupportWarning)
 
     global ssoptions
     ssoptions = SConscriptSettableOptions(options)
@@ -964,7 +965,12 @@ def _main(args, parser):
     progress_display("scons: " + opening_message)
     taskmaster = SCons.Taskmaster.Taskmaster(nodes, task_class, calc, order)
 
-    jobs = SCons.Job.Jobs(ssoptions.get('num_jobs'), taskmaster)
+    nj = ssoptions.get('num_jobs')
+    jobs = SCons.Job.Jobs(nj, taskmaster)
+    if nj > 1 and jobs.num_jobs == 1:
+        msg = "parallel builds are unsupported by this version of Python;\n" + \
+              "\tignoring -j or num_jobs option.\n"
+        SCons.Warnings.warn(SCons.Warnings.NoParallelSupportWarning, msg)
 
     try:
         jobs.run()
diff --git a/src/engine/SCons/Warnings.py b/src/engine/SCons/Warnings.py
index 436e663..cb78205 100644
--- a/src/engine/SCons/Warnings.py
+++ b/src/engine/SCons/Warnings.py
@@ -49,6 +49,9 @@ class ReservedVariableWarning(Warning):
 class CacheWriteErrorWarning(Warning):
     pass
 
+class NoParallelSupportWarning(Warning):
+    pass
+
 _warningAsException = 0
 
 # The below is a list of 2-tuples.  The first element is a class object.