JezK
Edit File: test_contextvars.py
from __future__ import print_function import gc import sys from functools import partial from unittest import skipUnless from unittest import skipIf from greenlet import greenlet from greenlet import getcurrent from . import TestCase try: from contextvars import Context from contextvars import ContextVar from contextvars import copy_context # From the documentation: # # Important: Context Variables should be created at the top module # level and never in closures. Context objects hold strong # references to context variables which prevents context variables # from being properly garbage collected. ID_VAR = ContextVar("id", default=None) VAR_VAR = ContextVar("var", default=None) ContextVar = None except ImportError: Context = ContextVar = copy_context = None # We don't support testing if greenlet's built-in context var support is disabled. @skipUnless(Context is not None, "ContextVar not supported") class ContextVarsTests(TestCase): def _new_ctx_run(self, *args, **kwargs): return copy_context().run(*args, **kwargs) def _increment(self, greenlet_id, callback, counts, expect): ctx_var = ID_VAR if expect is None: self.assertIsNone(ctx_var.get()) else: self.assertEqual(ctx_var.get(), expect) ctx_var.set(greenlet_id) for _ in range(2): counts[ctx_var.get()] += 1 callback() def _test_context(self, propagate_by): ID_VAR.set(0) callback = getcurrent().switch counts = dict((i, 0) for i in range(5)) lets = [ greenlet(partial( partial( copy_context().run, self._increment ) if propagate_by == "run" else self._increment, greenlet_id=i, callback=callback, counts=counts, expect=( i - 1 if propagate_by == "share" else 0 if propagate_by in ("set", "run") else None ) )) for i in range(1, 5) ] for let in lets: if propagate_by == "set": let.gr_context = copy_context() elif propagate_by == "share": let.gr_context = getcurrent().gr_context for i in range(2): counts[ID_VAR.get()] += 1 for let in lets: let.switch() if propagate_by == "run": # Must leave each context.run() in reverse order of entry for let in reversed(lets): let.switch() else: # No context.run(), so fine to exit in any order. for let in lets: let.switch() for let in lets: self.assertTrue(let.dead) # When using run(), we leave the run() as the greenlet dies, # and there's no context "underneath". When not using run(), # gr_context still reflects the context the greenlet was # running in. if propagate_by == 'run': self.assertIsNone(let.gr_context) else: self.assertIsNotNone(let.gr_context) if propagate_by == "share": self.assertEqual(counts, {0: 1, 1: 1, 2: 1, 3: 1, 4: 6}) else: self.assertEqual(set(counts.values()), set([2])) def test_context_propagated_by_context_run(self): self._new_ctx_run(self._test_context, "run") def test_context_propagated_by_setting_attribute(self): self._new_ctx_run(self._test_context, "set") def test_context_not_propagated(self): self._new_ctx_run(self._test_context, None) def test_context_shared(self): self._new_ctx_run(self._test_context, "share") def test_break_ctxvars(self): let1 = greenlet(copy_context().run) let2 = greenlet(copy_context().run) let1.switch(getcurrent().switch) let2.switch(getcurrent().switch) # Since let2 entered the current context and let1 exits its own, the # interpreter emits: # RuntimeError: cannot exit context: thread state references a different context object let1.switch() def test_not_broken_if_using_attribute_instead_of_context_run(self): let1 = greenlet(getcurrent().switch) let2 = greenlet(getcurrent().switch) let1.gr_context = copy_context() let2.gr_context = copy_context() let1.switch() let2.switch() let1.switch() let2.switch() def test_context_assignment_while_running(self): # pylint:disable=too-many-statements ID_VAR.set(None) def target(): self.assertIsNone(ID_VAR.get()) self.assertIsNone(gr.gr_context) # Context is created on first use ID_VAR.set(1) self.assertIsInstance(gr.gr_context, Context) self.assertEqual(ID_VAR.get(), 1) self.assertEqual(gr.gr_context[ID_VAR], 1) # Clearing the context makes it get re-created as another # empty context when next used old_context = gr.gr_context gr.gr_context = None # assign None while running self.assertIsNone(ID_VAR.get()) self.assertIsNone(gr.gr_context) ID_VAR.set(2) self.assertIsInstance(gr.gr_context, Context) self.assertEqual(ID_VAR.get(), 2) self.assertEqual(gr.gr_context[ID_VAR], 2) new_context = gr.gr_context getcurrent().parent.switch((old_context, new_context)) # parent switches us back to old_context self.assertEqual(ID_VAR.get(), 1) gr.gr_context = new_context # assign non-None while running self.assertEqual(ID_VAR.get(), 2) getcurrent().parent.switch() # parent switches us back to no context self.assertIsNone(ID_VAR.get()) self.assertIsNone(gr.gr_context) gr.gr_context = old_context self.assertEqual(ID_VAR.get(), 1) getcurrent().parent.switch() # parent switches us back to no context self.assertIsNone(ID_VAR.get()) self.assertIsNone(gr.gr_context) gr = greenlet(target) with self.assertRaisesRegex(AttributeError, "can't delete context attribute"): del gr.gr_context self.assertIsNone(gr.gr_context) old_context, new_context = gr.switch() self.assertIs(new_context, gr.gr_context) self.assertEqual(old_context[ID_VAR], 1) self.assertEqual(new_context[ID_VAR], 2) self.assertEqual(new_context.run(ID_VAR.get), 2) gr.gr_context = old_context # assign non-None while suspended gr.switch() self.assertIs(gr.gr_context, new_context) gr.gr_context = None # assign None while suspended gr.switch() self.assertIs(gr.gr_context, old_context) gr.gr_context = None gr.switch() self.assertIsNone(gr.gr_context) # Make sure there are no reference leaks gr = None gc.collect() self.assertEqual(sys.getrefcount(old_context), 2) self.assertEqual(sys.getrefcount(new_context), 2) def test_context_assignment_different_thread(self): import threading VAR_VAR.set(None) ctx = Context() is_running = threading.Event() should_suspend = threading.Event() did_suspend = threading.Event() should_exit = threading.Event() holder = [] def greenlet_in_thread_fn(): VAR_VAR.set(1) is_running.set() should_suspend.wait(10) VAR_VAR.set(2) getcurrent().parent.switch() holder.append(VAR_VAR.get()) def thread_fn(): gr = greenlet(greenlet_in_thread_fn) gr.gr_context = ctx holder.append(gr) gr.switch() did_suspend.set() should_exit.wait(10) gr.switch() del gr greenlet() # trigger cleanup thread = threading.Thread(target=thread_fn, daemon=True) thread.start() is_running.wait(10) gr = holder[0] # Can't access or modify context if the greenlet is running # in a different thread with self.assertRaisesRegex(ValueError, "running in a different"): getattr(gr, 'gr_context') with self.assertRaisesRegex(ValueError, "running in a different"): gr.gr_context = None should_suspend.set() did_suspend.wait(10) # OK to access and modify context if greenlet is suspended self.assertIs(gr.gr_context, ctx) self.assertEqual(gr.gr_context[VAR_VAR], 2) gr.gr_context = None should_exit.set() thread.join(10) self.assertEqual(holder, [gr, None]) # Context can still be accessed/modified when greenlet is dead: self.assertIsNone(gr.gr_context) gr.gr_context = ctx self.assertIs(gr.gr_context, ctx) # Otherwise we leak greenlets on some platforms. # XXX: Should be able to do this automatically del holder[:] gr = None thread = None def test_context_assignment_wrong_type(self): g = greenlet() with self.assertRaisesRegex(TypeError, "greenlet context must be a contextvars.Context or None"): g.gr_context = self @skipIf(Context is not None, "ContextVar supported") class NoContextVarsTests(TestCase): def test_contextvars_errors(self): let1 = greenlet(getcurrent().switch) self.assertFalse(hasattr(let1, 'gr_context')) with self.assertRaises(AttributeError): getattr(let1, 'gr_context') with self.assertRaises(AttributeError): let1.gr_context = None let1.switch() with self.assertRaises(AttributeError): getattr(let1, 'gr_context') with self.assertRaises(AttributeError): let1.gr_context = None del let1