sable: Rely on SASL PLAIN instead of NickServ to check for services availability

irctest/controllers/sable.py

@@ -14,6 +14,7 @@ from irctest.basecontrollers import (
     NotImplementedByController,
 )
 from irctest.cases import BaseServerTestCase
+from irctest.client_mock import ClientMock
 from irctest.exceptions import NoMessageException
 from irctest.patma import ANYSTR
 
@@ -554,6 +555,42 @@ class SableServicesController(BaseServicesController):
 
     faketime_cmd: Sequence[str]
 
+    def wait_for_services(self) -> None:
+        """Overrides the default implementation, as it relies on
+        ``PRIVMSG NickServ: HELP``, which always succeeds on Sable.
+
+        Instead, this relies on SASL PLAIN availability."""
+        if self.services_up:
+            # Don't check again if they are already available
+            return
+        self.server_controller.wait_for_port()
+
+        c = ClientMock(name="chkSASL", show_io=True)
+        c.connect(self.server_controller.hostname, self.server_controller.port)
+
+        def wait() -> None:
+            while True:
+                c.sendLine("CAP LS 302")
+                for msg in c.getMessages(synchronize=False):
+                    if msg.command == "CAP":
+                        assert msg.params[-2] == "LS", msg
+                        for cap in msg.params[-1].split():
+                            if cap.startswith("sasl="):
+                                mechanisms = cap.split("=", 1)[1].split(",")
+                                if "PLAIN" in mechanisms:
+                                    return
+                        else:
+                            if msg.params[0] == "*":
+                                # End of CAP LS
+                                time.sleep(self.server_controller.sync_sleep_time)
+
+        wait()
+
+        c.sendLine("QUIT")
+        c.getMessages()
+        c.disconnect()
+        self.services_up = True
+
     def run(self, protocol: str, server_hostname: str, server_port: int) -> None:
         assert protocol == "sable"
         assert self.server_controller.directory is not None