Merge pull request #1281 from exarkun/4002.reuse-chutney

Use an existing Chutney, if there is one

Fixes: ticket:4002

integration/conftest.py

@@ -1,6 +1,9 @@
 """
 Ported to Python 3.
 """
+
+from __future__ import annotations
+
 import sys
 import shutil
 from time import sleep
@@ -19,6 +22,7 @@ from eliot import (
     log_call,
 )
 
+from twisted.python.filepath import FilePath
 from twisted.python.procutils import which
 from twisted.internet.defer import DeferredList
 from twisted.internet.error import (
@@ -104,7 +108,7 @@ def reactor():
 
 @pytest.fixture(scope='session')
 @log_call(action_type=u"integration:temp_dir", include_args=[])
-def temp_dir(request):
+def temp_dir(request) -> str:
     """
     Invoke like 'py.test --keep-tempdir ...' to avoid deleting the temp-dir
     """
@@ -446,7 +450,23 @@ def bob(reactor, temp_dir, introducer_furl, flog_gatherer, storage_nodes, reques
 @pytest.fixture(scope='session')
 @pytest.mark.skipif(sys.platform.startswith('win'),
                     'Tor tests are unstable on Windows')
-def chutney(reactor, temp_dir):
+def chutney(reactor, temp_dir: str) -> tuple[str, dict[str, str]]:
+    # Try to find Chutney already installed in the environment.
+    try:
+        import chutney
+    except ImportError:
+        # Nope, we'll get our own in a moment.
+        pass
+    else:
+        # We already have one, just use it.
+        return (
+            # from `checkout/lib/chutney/__init__.py` we want to get back to
+            # `checkout` because that's the parent of the directory with all
+            # of the network definitions.  So, great-grand-parent.
+            FilePath(chutney.__file__).parent().parent().parent().path,
+            # There's nothing to add to the environment.
+            {},
+        )
 
     chutney_dir = join(temp_dir, 'chutney')
     mkdir(chutney_dir)
@@ -488,88 +508,58 @@ def chutney(reactor, temp_dir):
     )
     pytest_twisted.blockon(proto.done)
 
-    return chutney_dir
+    return (chutney_dir, {"PYTHONPATH": join(chutney_dir, "lib")})
 
 
 @pytest.fixture(scope='session')
 @pytest.mark.skipif(sys.platform.startswith('win'),
                     reason='Tor tests are unstable on Windows')
 def tor_network(reactor, temp_dir, chutney, request):
+    """
+    Build a basic Tor network.
 
-    # this is the actual "chutney" script at the root of a chutney checkout
-    chutney_dir = chutney
-    chut = join(chutney_dir, 'chutney')
+    :param chutney: The root directory of a Chutney checkout and a dict of
+        additional environment variables to set so a Python process can use
+        it.
+
+    :return: None
+    """
+    chutney_root, chutney_env = chutney
+    basic_network = join(chutney_root, 'networks', 'basic')
+
+    env = environ.copy()
+    env.update(chutney_env)
+    chutney_argv = (sys.executable, '-m', 'chutney.TorNet')
+    def chutney(argv):
+        proto = _DumpOutputProtocol(None)
+        reactor.spawnProcess(
+            proto,
+            sys.executable,
+            chutney_argv + argv,
+            path=join(chutney_root),
+            env=env,
+        )
+        return proto.done
 
     # now, as per Chutney's README, we have to create the network
     # ./chutney configure networks/basic
     # ./chutney start networks/basic
-
-    env = environ.copy()
-    env.update({"PYTHONPATH": join(chutney_dir, "lib")})
-    proto = _DumpOutputProtocol(None)
-    reactor.spawnProcess(
-        proto,
-        sys.executable,
-        (
-            sys.executable, '-m', 'chutney.TorNet', 'configure',
-            join(chutney_dir, 'networks', 'basic'),
-        ),
-        path=join(chutney_dir),
-        env=env,
-    )
-    pytest_twisted.blockon(proto.done)
-
-    proto = _DumpOutputProtocol(None)
-    reactor.spawnProcess(
-        proto,
-        sys.executable,
-        (
-            sys.executable, '-m', 'chutney.TorNet', 'start',
-            join(chutney_dir, 'networks', 'basic'),
-        ),
-        path=join(chutney_dir),
-        env=env,
-    )
-    pytest_twisted.blockon(proto.done)
+    pytest_twisted.blockon(chutney(("configure", basic_network)))
+    pytest_twisted.blockon(chutney(("start", basic_network)))
 
     # print some useful stuff
-    proto = _CollectOutputProtocol()
-    reactor.spawnProcess(
-        proto,
-        sys.executable,
-        (
-            sys.executable, '-m', 'chutney.TorNet', 'status',
-            join(chutney_dir, 'networks', 'basic'),
-        ),
-        path=join(chutney_dir),
-        env=env,
-    )
     try:
-        pytest_twisted.blockon(proto.done)
+        pytest_twisted.blockon(chutney(("status", basic_network)))
     except ProcessTerminated:
-        print("Chutney.TorNet status failed (continuing):")
-        print(proto.output.getvalue())
+        print("Chutney.TorNet status failed (continuing)")
 
     def cleanup():
         print("Tearing down Chutney Tor network")
-        proto = _CollectOutputProtocol()
-        reactor.spawnProcess(
-            proto,
-            sys.executable,
-            (
-                sys.executable, '-m', 'chutney.TorNet', 'stop',
-                join(chutney_dir, 'networks', 'basic'),
-            ),
-            path=join(chutney_dir),
-            env=env,
-        )
         try:
-            block_with_timeout(proto.done, reactor)
+            block_with_timeout(chutney(("stop", basic_network)), reactor)
         except ProcessTerminated:
             # If this doesn't exit cleanly, that's fine, that shouldn't fail
             # the test suite.
             pass
 
     request.addfinalizer(cleanup)
-
-    return chut