Restore dummy_threading and _dummy_thread, but deprecate them (bpo-31370) (#3648)
diff --git a/Lib/_dummy_thread.py b/Lib/_dummy_thread.py
new file mode 100644
index 0000000..a2cae54
--- /dev/null
+++ b/Lib/_dummy_thread.py
@@ -0,0 +1,163 @@
+"""Drop-in replacement for the thread module.
+
+Meant to be used as a brain-dead substitute so that threaded code does
+not need to be rewritten for when the thread module is not present.
+
+Suggested usage is::
+
+ try:
+ import _thread
+ except ImportError:
+ import _dummy_thread as _thread
+
+"""
+# Exports only things specified by thread documentation;
+# skipping obsolete synonyms allocate(), start_new(), exit_thread().
+__all__ = ['error', 'start_new_thread', 'exit', 'get_ident', 'allocate_lock',
+ 'interrupt_main', 'LockType']
+
+# A dummy value
+TIMEOUT_MAX = 2**31
+
+# NOTE: this module can be imported early in the extension building process,
+# and so top level imports of other modules should be avoided. Instead, all
+# imports are done when needed on a function-by-function basis. Since threads
+# are disabled, the import lock should not be an issue anyway (??).
+
+error = RuntimeError
+
+def start_new_thread(function, args, kwargs={}):
+ """Dummy implementation of _thread.start_new_thread().
+
+ Compatibility is maintained by making sure that ``args`` is a
+ tuple and ``kwargs`` is a dictionary. If an exception is raised
+ and it is SystemExit (which can be done by _thread.exit()) it is
+ caught and nothing is done; all other exceptions are printed out
+ by using traceback.print_exc().
+
+ If the executed function calls interrupt_main the KeyboardInterrupt will be
+ raised when the function returns.
+
+ """
+ if type(args) != type(tuple()):
+ raise TypeError("2nd arg must be a tuple")
+ if type(kwargs) != type(dict()):
+ raise TypeError("3rd arg must be a dict")
+ global _main
+ _main = False
+ try:
+ function(*args, **kwargs)
+ except SystemExit:
+ pass
+ except:
+ import traceback
+ traceback.print_exc()
+ _main = True
+ global _interrupt
+ if _interrupt:
+ _interrupt = False
+ raise KeyboardInterrupt
+
+def exit():
+ """Dummy implementation of _thread.exit()."""
+ raise SystemExit
+
+def get_ident():
+ """Dummy implementation of _thread.get_ident().
+
+ Since this module should only be used when _threadmodule is not
+ available, it is safe to assume that the current process is the
+ only thread. Thus a constant can be safely returned.
+ """
+ return 1
+
+def allocate_lock():
+ """Dummy implementation of _thread.allocate_lock()."""
+ return LockType()
+
+def stack_size(size=None):
+ """Dummy implementation of _thread.stack_size()."""
+ if size is not None:
+ raise error("setting thread stack size not supported")
+ return 0
+
+def _set_sentinel():
+ """Dummy implementation of _thread._set_sentinel()."""
+ return LockType()
+
+class LockType(object):
+ """Class implementing dummy implementation of _thread.LockType.
+
+ Compatibility is maintained by maintaining self.locked_status
+ which is a boolean that stores the state of the lock. Pickling of
+ the lock, though, should not be done since if the _thread module is
+ then used with an unpickled ``lock()`` from here problems could
+ occur from this class not having atomic methods.
+
+ """
+
+ def __init__(self):
+ self.locked_status = False
+
+ def acquire(self, waitflag=None, timeout=-1):
+ """Dummy implementation of acquire().
+
+ For blocking calls, self.locked_status is automatically set to
+ True and returned appropriately based on value of
+ ``waitflag``. If it is non-blocking, then the value is
+ actually checked and not set if it is already acquired. This
+ is all done so that threading.Condition's assert statements
+ aren't triggered and throw a little fit.
+
+ """
+ if waitflag is None or waitflag:
+ self.locked_status = True
+ return True
+ else:
+ if not self.locked_status:
+ self.locked_status = True
+ return True
+ else:
+ if timeout > 0:
+ import time
+ time.sleep(timeout)
+ return False
+
+ __enter__ = acquire
+
+ def __exit__(self, typ, val, tb):
+ self.release()
+
+ def release(self):
+ """Release the dummy lock."""
+ # XXX Perhaps shouldn't actually bother to test? Could lead
+ # to problems for complex, threaded code.
+ if not self.locked_status:
+ raise error
+ self.locked_status = False
+ return True
+
+ def locked(self):
+ return self.locked_status
+
+ def __repr__(self):
+ return "<%s %s.%s object at %s>" % (
+ "locked" if self.locked_status else "unlocked",
+ self.__class__.__module__,
+ self.__class__.__qualname__,
+ hex(id(self))
+ )
+
+# Used to signal that interrupt_main was called in a "thread"
+_interrupt = False
+# True when not executing in a "thread"
+_main = True
+
+def interrupt_main():
+ """Set _interrupt flag to True to have start_new_thread raise
+ KeyboardInterrupt upon exiting."""
+ if _main:
+ raise KeyboardInterrupt
+ else:
+ global _interrupt
+ _interrupt = True