Stop using twisted.internet.defer.returnValue

`defer.returnValue` was only needed in Python 2; in Python 3, a simple
`return` is fine.

`twisted.internet.defer.returnValue` is deprecated as of Twisted 24.7.0.

autobahn/twisted/cryptosign.py

@@ -27,7 +27,7 @@
 
 from autobahn.wamp.cryptosign import HAS_CRYPTOSIGN, CryptosignKey
 
-from twisted.internet.defer import inlineCallbacks, returnValue
+from twisted.internet.defer import inlineCallbacks
 
 __all__ = [
     'HAS_CRYPTOSIGN_SSHAGENT'
@@ -118,7 +118,7 @@ def on_connect(agent):
 
                 if key_data:
                     key = signing.VerifyKey(key_data)
-                    returnValue(cls(key, key_comment, reactor))
+                    return cls(key, key_comment, reactor)
                 else:
                     raise Exception("Ed25519 key not held in ssh-agent")
 
@@ -147,6 +147,6 @@ def on_connect(agent):
 
                 agent.transport.loseConnection()
 
-                returnValue(signature)
+                return signature
 
             return d.addCallback(on_connect)

autobahn/twisted/wamp.py

@@ -596,19 +596,7 @@ def add2(a, b):
               return a + b
 
         If the function `yields` (is a co-routine), the `@inlineCallbacks` decorator
-        will be applied automatically to it. In that case, if you wish to return something,
-        you should use `returnValue`:
-
-        :Example:
-
-        .. code-block:: python
-
-           from twisted.internet.defer import returnValue
-
-           @app.register('com.myapp.add2')
-           def add2(a, b):
-              res = yield stuff(a, b)
-              returnValue(res)
+        will be applied automatically to it.
 
         :param uri: The URI of the procedure to register under.
         :type uri: unicode

autobahn/wamp/test/test_wamp_protocol.py

@@ -29,7 +29,7 @@
 
 if os.environ.get('USE_TWISTED', False):
 
-    from twisted.internet.defer import inlineCallbacks, Deferred, returnValue
+    from twisted.internet.defer import inlineCallbacks, Deferred
     from twisted.internet.defer import succeed, fail, DeferredList
     from twisted.trial import unittest
     import twisted
@@ -814,7 +814,7 @@ def bing(details=None):
                 for i in range(10):
                     details.progress(i)
                     yield succeed(i)
-                returnValue(42)
+                return 42
 
             progressive = list(map(lambda _: Deferred(), range(10)))
 
@@ -850,7 +850,7 @@ def bing(arg, details=None, key=None):
                 self.assertEqual('arg', arg)
                 details.progress('life', something='nothing')
                 yield succeed('meaning of')
-                returnValue(42)
+                return 42
 
             got_progress = Deferred()
             progress_error = NameError('foo')
@@ -899,7 +899,7 @@ def bing(details=None):
                 self.assertTrue(details.progress is not None)
                 details.progress()
                 yield succeed(True)
-                returnValue(42)
+                return 42
 
             got_progress = Deferred()
 
@@ -931,7 +931,7 @@ def bing(details=None):
                 self.assertTrue(details.progress is not None)
                 details.progress(key='word')
                 yield succeed(True)
-                returnValue(42)
+                return 42
 
             got_progress = Deferred()
 

docs/asynchronous-programming.rst

@@ -246,13 +246,13 @@ Now, when converted to ``inlineCallbacks``, the code becomes:
    :emphasize-lines: 5,7,8
 
    from twisted.internet import reactor
-   from twisted.internet.defer import inlineCallbacks, returnValue
+   from twisted.internet.defer import inlineCallbacks
    from autobahn.twisted.util import sleep
 
    @inlineCallbacks
    def slow_square(x):
       yield sleep(1)
-      returnValue(x * x)
+      return x * x
 
    @inlineCallbacks
    def test():
@@ -268,11 +268,6 @@ Have a look at the highlighted lines - here is what we do:
 
 1. Decorating our squaring function with ``inlineCallbacks`` (line 5). Doing so marks the function as a coroutine which allows us to use this sequential looking coding style.
 2. Inside the function, we simulate the slow execution by sleeping for a second (line 7). However, we are sleeping in a non-blocking way (``autobahn.twisted.util.sleep``). The ``yield`` will put the coroutine aside until the sleep returns.
-3. To return values from Twisted coroutines, we need to use ``returnValue`` (line 8).
-
-.. note::
-
-   The reason ``returnValue`` is necessary goes deep into implementation details of Twisted and Python. In short: co-routines in Python 2 with Twisted are simulated using exceptions. Only Python 3.3+ has gotten native support for co-routines using the new yield from statement, Python 3.5+ use await statement and it is the new recommended method.
 
 In above, we are using a little helper ``autobahn.twisted.util.sleep`` for sleeping "inline". The helper is really trivial:
 
@@ -374,8 +369,7 @@ Now, when converted to ``asyncio.coroutine``, the code becomes:
 The main differences (on surface) are:
 
 1. The declaration of the function with ``async`` keyword (line 3) in asyncio versus the decorator ``@defer.inlineCallbacks`` with Twisted
-2. The use of ``defer.returnValue`` in Twisted for returning values whereas in asyncio, you can use plain returns (line 6)
-3. The use of ``await`` in asyncio, versus ``yield`` in Twisted (line 5)
-4. The auxiliary code to get the event loop started and stopped
+2. The use of ``await`` in asyncio, versus ``yield`` in Twisted (line 5)
+3. The auxiliary code to get the event loop started and stopped
 
 Most of the examples that follow will show code for both Twisted and asyncio, unless the conversion is trivial.

docs/listings/programming.py

@@ -1,7 +1,7 @@
 from autobahn.twisted.component import Component, run
 from autobahn.twisted.util import sleep
 from autobahn.wamp.types import RegisterOptions
-from twisted.internet.defer import inlineCallbacks, returnValue
+from twisted.internet.defer import inlineCallbacks
 
 # to see how this works on the Crossbar.io side, see the example
 # router configuration in:
@@ -61,7 +61,7 @@ def foo(*args, **kw):
         print("  returning in {}".format(x))
         yield sleep(1)
     print("returning '42'")
-    returnValue(42)
+    return 42
 
 
 if __name__ == "__main__":

docs/listings/tx_complete.py

@@ -1,7 +1,7 @@
 from autobahn.twisted.component import Component, run
 from autobahn.twisted.util import sleep
 from autobahn.wamp.types import RegisterOptions
-from twisted.internet.defer import inlineCallbacks, returnValue
+from twisted.internet.defer import inlineCallbacks
 
 # to see how this works on the Crossbar.io side, see the example
 # router configuration in:
@@ -61,7 +61,7 @@ def foo(*args, **kw):
         print("  returning in {}".format(x))
         yield sleep(1)
     print("returning '42'")
-    returnValue(42)
+    return 42
 
 
 if __name__ == "__main__":

docs/work/apps.rst

@@ -80,16 +80,14 @@ a more convincing demo.
 If you use "yield" inside any of the callbacks, `@inlineCallbacks` will
 be applied automatically. It means every yielded line will be be added in
 a Deferred so they execute sequentially, in regards to the other yielded
-lines in the same function. In that case, you should not `return`, but use
-`returnValue`.
+lines in the same function.
 
 :Example:
 
 .. code-block:: python
 
    from autobahn.twisted.wamp import Application
 
-   from twisted.internet.defer import returnValue
    from twisted.web.client import Agent
 
    app = Application()
@@ -106,9 +104,7 @@ lines in the same function. In that case, you should not `return`, but use
       # Asynchronous GET request on the url
       d = yield agent.request('GET', url)
 
-      # Using returnValue and not return because the whole
-      # procedure is a coroutine since we used yield.
-      returnValue(d.code)
+      return d.code
 
    @app.signal('onjoin')
    def entry_point():

examples/run-all-examples.py

@@ -22,7 +22,7 @@
 from colorama import Fore
 
 from twisted.internet.protocol import ProcessProtocol
-from twisted.internet.defer import inlineCallbacks, Deferred, returnValue
+from twisted.internet.defer import inlineCallbacks, Deferred
 from twisted.internet.error import ProcessExitedAlready
 from twisted.internet import reactor
 from twisted.internet.task import react
@@ -108,7 +108,7 @@ def start_crossbar():
     else:
         DELAY = 2.
     yield sleep(DELAY)
-    returnValue(protocol)
+    return protocol
 
 
 @inlineCallbacks
@@ -124,7 +124,7 @@ def start_example(py_fname, color, prefix='', exe=sys.executable):
     reactor.spawnProcess(protocol, exe, args, path='.', env=env)
 
     yield launched
-    returnValue(protocol)
+    return protocol
 
 
 def print_banner(title):
@@ -232,8 +232,8 @@ def main(reactor):
         print()
         print("Success!")
         print("  ...all the examples neither crashed nor burned...")
-        returnValue(0)
-    returnValue(5)
+        return 0
+    return 5
 
 
 if __name__ == '__main__':

examples/twisted/wamp/app/crochet/example2/server.py

@@ -30,7 +30,6 @@
 # this MUST be called _before_ any Autobahn or Twisted imports!
 setup()
 
-from twisted.internet.defer import returnValue  # noqa
 from autobahn.twisted.util import sleep  # noqa
 from autobahn.twisted.wamp import Application  # noqa
 
@@ -50,7 +49,7 @@ def square(x):
 def slowsquare(x):
     print("slowsquare() called with {}".format(x))
     yield sleep(2)
-    returnValue(x * x)
+    return x * x
 
 
 # the following are synchronous wrappers around the asynchronous WAMP code

examples/twisted/wamp/app/hello/hello.py

@@ -25,7 +25,6 @@
 ###############################################################################
 
 from os import environ
-from twisted.internet.defer import returnValue
 from autobahn.twisted.wamp import Application
 
 
@@ -42,7 +41,7 @@ def add2(a, b):
 def hello():
     print("hello() called")
     res = yield app.session.call('com.example.add2', 2, 3)
-    returnValue("Hello {}".format(res))
+    return "Hello {}".format(res)
 
 
 @app.signal('onjoined')

examples/twisted/wamp/app/klein/example1/server_web.py

@@ -24,7 +24,7 @@
 #
 ###############################################################################
 
-from twisted.internet.defer import inlineCallbacks, returnValue
+from twisted.internet.defer import inlineCallbacks
 from klein import Klein
 from autobahn.twisted.wamp import Application
 
@@ -37,7 +37,7 @@
 def square_submit(request):
     x = int(request.args.get('x', [0])[0])
     res = yield wampapp.session.call('com.example.square', x)
-    returnValue("{} squared is {}".format(x, res))
+    return "{} squared is {}".format(x, res)
 
 
 if __name__ == "__main__":

examples/twisted/wamp/app/klein/example2/server.py

@@ -27,7 +27,7 @@
 import jinja2
 from klein import Klein
 
-from twisted.internet.defer import inlineCallbacks, returnValue
+from twisted.internet.defer import inlineCallbacks
 from autobahn.twisted.wamp import Application
 
 
@@ -62,8 +62,7 @@ def home(request):
 def square(request, x):
     result = yield wampapp.session.call('com.example.square', x)
     page = webapp.templates.get_template('result.html')
-    content = page.render(x=x, result=result)
-    returnValue(content)
+    return page.render(x=x, result=result)
 
 
 @webapp.route('/square/submit', methods=['POST'])

examples/twisted/wamp/component/backend.py

@@ -3,7 +3,7 @@
 from autobahn.twisted.component import Component, run
 from autobahn.twisted.util import sleep
 from autobahn.wamp.types import RegisterOptions
-from twisted.internet.defer import inlineCallbacks, returnValue
+from twisted.internet.defer import inlineCallbacks
 from twisted.internet._sslverify import OpenSSLCertificateAuthorities
 from twisted.internet.ssl import CertificateOptions
 from twisted.internet.ssl import optionsForClientTLS, Certificate
@@ -73,7 +73,7 @@ def foo(*args, **kw):
         print("  returning in {}".format(x))
         yield sleep(1)
     print("returning '42'")
-    returnValue(42)
+    return 42
 
 
 if __name__ == "__main__":

examples/twisted/wamp/rpc/progress/backend.py

@@ -25,7 +25,7 @@
 ###############################################################################
 
 from os import environ
-from twisted.internet.defer import inlineCallbacks, returnValue
+from twisted.internet.defer import inlineCallbacks
 
 from autobahn.wamp.types import RegisterOptions
 from autobahn.twisted.util import sleep
@@ -51,7 +51,7 @@ def longop(n, details=None):
             else:
                 # process like a normal call (not producing progressive results)
                 yield sleep(1 * n)
-            returnValue(n)
+            return n
 
         yield self.register(longop, 'com.myapp.longop', RegisterOptions(details_arg='details'))
 

examples/twisted/wamp/rpc/slowsquare/backend.py

@@ -25,8 +25,7 @@
 ###############################################################################
 
 from os import environ
-from twisted.internet.defer import inlineCallbacks, \
-    returnValue
+from twisted.internet.defer import inlineCallbacks
 
 from autobahn.twisted.wamp import ApplicationSession, ApplicationRunner
 from autobahn.twisted.util import sleep
@@ -49,7 +48,7 @@ def square(x):
         @inlineCallbacks
         def slowsquare(x, delay=1):
             yield sleep(delay)
-            returnValue(x * x)
+            return x * x
 
         yield self.register(slowsquare, 'com.math.slowsquare')
 

examples/twisted/websocket/slowsquare/server.py

@@ -29,8 +29,7 @@
 
 import json
 from twisted.internet.defer import Deferred, \
-    inlineCallbacks, \
-    returnValue
+    inlineCallbacks
 
 
 def sleep(delay):
@@ -47,7 +46,7 @@ def slowsquare(self, x):
             raise Exception("number too large")
         else:
             yield sleep(1)
-            returnValue(x * x)
+            return x * x
 
     @inlineCallbacks
     def onMessage(self, payload, isBinary):