nixos/test-driver: rework timeout for wait_for_console_text (#526952)

nixos/lib/test-driver/src/test_driver/machine/__init__.py

@@ -1164,24 +1164,25 @@ class QemuMachine(BaseMachine):
         # to match multiline regexes.
         console = io.StringIO()
 
-        def console_matches(_last_try: bool) -> bool:
+        def console_matches(_last_try: bool, block: bool = False) -> bool:
             nonlocal console
             try:
-                # This will return as soon as possible and
-                # sleep 1 second.
-                console.write(self.last_lines.get(block=False))
+                while True:
+                    # This will return as soon as possible and
+                    # sleep 1 second.
+                    console.write(self.last_lines.get(block=block))
+                    console.seek(0)
+                    matches = re.search(regex, console.read())
+                    if matches is not None:
+                        return True
             except queue.Empty:
-                pass
-            console.seek(0)
-            matches = re.search(regex, console.read())
-            return matches is not None
+                return False
 
         with self.nested(f"waiting for {regex} to appear on console"):
             if timeout is not None:
                 retry(console_matches, timeout)
             else:
-                while not console_matches(False):
-                    pass
+                console_matches(False, block=True)
 
     def get_console_log(self) -> str:
         """

nixos/tests/all-tests.nix

@@ -153,6 +153,7 @@ in
     console-log = runTest ./nixos-test-driver/console-log.nix;
     containers = runTest ./nixos-test-driver/containers.nix;
     skip-typecheck = runTest ./nixos-test-driver/skip-typecheck.nix;
+    console-timeout = runTest ./nixos-test-driver/console-timeout.nix;
     options-doc-regression = import ./nixos-test-driver/options-doc-regression.nix { inherit pkgs; };
     driver-timeout =
       pkgs.runCommand "ensure-timeout-induced-failure"

nixos/tests/nixos-test-driver/console-timeout.nix

@@ -0,0 +1,26 @@
+{ pkgs, lib, ... }:
+{
+  name = "console-timeout";
+
+  nodes.machine = {
+    systemd.services.generate-output.script = ''
+      echo "match that"
+      sleep 1
+
+      for i in $(seq 15); do
+        echo "line $i"
+      done
+
+      echo "match this"
+    '';
+  };
+
+  testScript = ''
+    machine.start()
+    machine.wait_for_unit("multi-user.target")
+
+    machine.systemctl("start generate-output")
+    machine.wait_for_console_text("match that")
+    machine.wait_for_console_text("match this", timeout=10)
+  '';
+}