nixos/test: Use retry() in all looping functions that need timeouts

nixos/lib/test-driver/test-driver.py

@@ -312,8 +312,13 @@ class Machine:
         self.monitor.send(message)
         return self.wait_for_monitor_prompt()
 
-    def wait_for_unit(self, unit: str, user: Optional[str] = None) -> bool:
-        while True:
+    def wait_for_unit(self, unit: str, user: Optional[str] = None) -> None:
+        """Wait for a systemd unit to get into "active" state.
+        Throws exceptions on "failed" and "inactive" states as well as
+        after timing out.
+        """
+
+        def check_active(_: Any) -> bool:
             info = self.get_unit_info(unit, user)
             state = info["ActiveState"]
             if state == "failed":
@@ -329,8 +334,10 @@ class Machine:
                                 'unit "{}" is inactive and there ' "are no pending jobs"
                             ).format(unit)
                         )
-            if state == "active":
-                return True
+
+            return state == "active"
+
+        retry(check_active)
 
     def get_unit_info(self, unit: str, user: Optional[str] = None) -> Dict[str, str]:
         status, lines = self.systemctl('--no-pager show "{}"'.format(unit), user)
@@ -421,18 +428,34 @@ class Machine:
                     )
 
     def wait_until_succeeds(self, command: str) -> str:
+        """Wait until a command returns success and return its output.
+        Throws an exception on timeout.
+        """
+        output = ""
+
+        def check_success(_: Any) -> bool:
+            nonlocal output
+            status, output = self.execute(command)
+            return status == 0
+
         with self.nested("waiting for success: {}".format(command)):
-            while True:
-                status, output = self.execute(command)
-                if status == 0:
-                    return output
+            retry(check_success)
+            return output
 
     def wait_until_fails(self, command: str) -> str:
+        """Wait until a command returns failure.
+        Throws an exception on timeout.
+        """
+        output = ""
+
+        def check_failure(_: Any) -> bool:
+            nonlocal output
+            status, output = self.execute(command)
+            return status != 0
+
         with self.nested("waiting for failure: {}".format(command)):
-            while True:
-                status, output = self.execute(command)
-                if status != 0:
-                    return output
+            retry(check_failure)
+            return output
 
     def wait_for_shutdown(self) -> None:
         if not self.booted:
@@ -453,25 +476,38 @@ class Machine:
         )
         return output
 
-    def wait_until_tty_matches(self, tty: str, regexp: str) -> bool:
+    def wait_until_tty_matches(self, tty: str, regexp: str) -> None:
+        """Wait until the visible output on the chosen TTY matches regular
+        expression. Throws an exception on timeout.
+        """
         matcher = re.compile(regexp)
+
+        def tty_matches(last: bool) -> bool:
+            text = self.get_tty_text(tty)
+            if last:
+                self.log(
+                    f"Last chance to match /{regexp}/ on TTY{tty}, "
+                    f"which currently contains: {text}"
+                )
+            return len(matcher.findall(text)) > 0
+
         with self.nested("waiting for {} to appear on tty {}".format(regexp, tty)):
-            while True:
-                text = self.get_tty_text(tty)
-                if len(matcher.findall(text)) > 0:
-                    return True
+            retry(tty_matches)
 
     def send_chars(self, chars: List[str]) -> None:
         with self.nested("sending keys ‘{}‘".format(chars)):
             for char in chars:
                 self.send_key(char)
 
-    def wait_for_file(self, filename: str) -> bool:
+    def wait_for_file(self, filename: str) -> None:
+        """Waits until the file exists in machine's file system."""
+
+        def check_file(_: Any) -> bool:
+            status, _ = self.execute("test -e {}".format(filename))
+            return status == 0
+
         with self.nested("waiting for file ‘{}‘".format(filename)):
-            while True:
-                status, _ = self.execute("test -e {}".format(filename))
-                if status == 0:
-                    return True
+            retry(check_file)
 
     def wait_for_open_port(self, port: int) -> None:
         def port_is_open(_: Any) -> bool:
@@ -494,8 +530,8 @@ class Machine:
     def stop_job(self, jobname: str, user: Optional[str] = None) -> Tuple[int, str]:
         return self.systemctl("stop {}".format(jobname), user)
 
-    def wait_for_job(self, jobname: str) -> bool:
-        return self.wait_for_unit(jobname)
+    def wait_for_job(self, jobname: str) -> None:
+        self.wait_for_unit(jobname)
 
     def connect(self) -> None:
         if self.connected:
@@ -700,18 +736,20 @@ class Machine:
         """Wait until it is possible to connect to the X server.  Note that
         testing the existence of /tmp/.X11-unix/X0 is insufficient.
         """
+
+        def check_x(_: Any) -> bool:
+            cmd = (
+                "journalctl -b SYSLOG_IDENTIFIER=systemd | "
+                + 'grep "Reached target Current graphical"'
+            )
+            status, _ = self.execute(cmd)
+            if status != 0:
+                return False
+            status, _ = self.execute("[ -e /tmp/.X11-unix/X0 ]")
+            return status == 0
+
         with self.nested("waiting for the X11 server"):
-            while True:
-                cmd = (
-                    "journalctl -b SYSLOG_IDENTIFIER=systemd | "
-                    + 'grep "Reached target Current graphical"'
-                )
-                status, _ = self.execute(cmd)
-                if status != 0:
-                    continue
-                status, _ = self.execute("[ -e /tmp/.X11-unix/X0 ]")
-                if status == 0:
-                    return
+            retry(check_x)
 
     def get_window_names(self) -> List[str]:
         return self.succeed(