Let a second copy yield to the instance already running

listen() was the whole of the single-instance check and it cannot be one:
a Windows named pipe takes a second server on the same name rather than
refusing it, and everywhere else removeServer() first takes the live socket
away from the instance holding it. Starting Dikte over a running Dikte then
left two whole copies up, two tray icons and all, and the newer one's
sweep() killed the whisper the older one was answering dictations with. On
a machine that sleeps instead of logging out, that is one Start Menu click
away, and it cost a real dictation before it was understood.

A QLockFile in the data directory closes the race on all three systems,
taken before the QApplication is even built, and behind it the probe is the
side-effect-free status verb: the Settings window opens as the sign of life
only when a bare second start deliberately asks for it, not as a byproduct
of a probe racing a forwarded toggle. The two Windows relaunch dances
collapse into one ipc.respawn.

The checkout installer and the packaged setup each kept an autostart the
other could not see, so a machine that tried both started two copies at
every sign-in: each autostart now removes the other's entry, the silent
every-start repair backs off from a Run value whose target still exists,
and each uninstaller deletes the shared dikte.cmd only when the shim
names its own install.

Co-Authored-By: Claude Fable 5 <[email protected]>

dikte/app.py

@@ -1122,6 +1122,15 @@ def _stay_out_of_the_dock():
 def run_app(args):
     command = args[0] if args else ""
 
+    # One Dikte per user, checked by asking rather than by listening: see
+    # ipc.already_serving. Before the QApplication, so a second copy costs a
+    # moment and not a second tray icon.
+    if ipc.already_serving():
+        print("dikte: already running; its Settings window has the attention")
+        if command:
+            ipc.send(command)
+        return 0
+
     app = QApplication(sys.argv)
     app.setApplicationName("Dikte")
     app.setDesktopFileName("dikte")

dikte/integrate.py

@@ -56,6 +56,17 @@ def packaged():
     return bool(getattr(sys, "frozen", False))
 
 
+def windowed_executable(executable=None):
+    """The windowed executable installed beside this one, or None.
+
+    Beside rather than at a known place, because the setup program lays the two
+    executables into the same directory wherever that directory was put: asking
+    from either of them finds the other without knowing where the install is.
+    """
+    windowed = pathlib.Path(executable or sys.executable).with_name(WINDOWS_APP)
+    return windowed if windowed.is_file() else None
+
+
 def target():
     """The file a launcher has to name to start this build again.
 
@@ -74,8 +85,8 @@ def target():
         # The windowed executable, whichever of the two is running: the console
         # one is what the `dikte` command names, and a sign-in that started
         # that one would open a console window nobody asked for.
-        windowed = executable.with_name(WINDOWS_APP)
+        windowed = windowed_executable(executable)
-        if windowed.is_file():
+        if windowed is not None:
             return windowed
     return executable
 
@@ -572,24 +583,60 @@ def _run_entry_name():
     return f"HKCU\\{RUN_KEY}\\{RUN_VALUE}"
 
 
+def _run_target(value):
+    """The executable a Run value names, out of the quoting the setup wrote.
+
+    Only the first word matters here: it is the file whose existence says
+    whether the entry still starts anything.
+    """
+    if value.startswith('"'):
+        closing = value.find('"', 1)
+        return value[1:closing] if closing > 0 else ""
+    return value.split(" ", 1)[0]
+
+
+def _startup_shortcut():
+    """Where install.ps1 -Autostart puts a checkout's sign-in entry."""
+    appdata = os.environ.get("APPDATA")
+    if not appdata:
+        return None
+    return (pathlib.Path(appdata) / "Microsoft" / "Windows" / "Start Menu"
+            / "Programs" / "Startup" / "Dikte.lnk")
+
+
 def _windows_install(app, force=False):
     """Point the autostart entry at this build. What changed.
 
     Only `force`, which is what typing `dikte integrate` means, creates one.
     The call on every start repairs an entry that is already there and names an
-    executable somewhere else, which is what an installation moved to another
+    executable that is gone, which is what an installation moved to another
-    drive or reinstalled into another directory leaves behind; somebody who
+    drive or reinstalled into another directory leaves behind. An entry naming
-    unticked the box in the wizard, or turned it off since, is not asked again
+    an executable that still exists is another installation that still works,
-    by every start.
+    and is stood aside for the way the Linux half stands aside for another
+    menu entry; somebody who unticked the box in the wizard, or turned it off
+    since, is not asked again by every start either.
     """
     command = f'"{app}"'
     current = _run_entry()
+    changed = []
+    if force:
+        # install.ps1 -Autostart wrote this for a checkout. The Run value
+        # written below replaces it, and both left in place would be two
+        # Diktes at every sign-in. Only on force: the silent call on every
+        # start has not been asked to move the machine off its checkout.
+        shortcut = _startup_shortcut()
+        if shortcut is not None and shortcut.is_file():
+            shortcut.unlink()
+            changed.append(shortcut)
     if not current and not force:
-        return []
+        return changed
-    if current == command:
+    if current != command:
-        return []
+        theirs = _run_target(current) if current else ""
-    _write_run_entry(command)
+        if not force and theirs and theirs != str(app) and os.path.exists(theirs):
-    return [_run_entry_name()]
+            return changed
+        _write_run_entry(command)
+        changed.append(_run_entry_name())
+    return changed
 
 
 def _windows_remove():

dikte/ipc.py

@@ -11,11 +11,14 @@ shortcut may still send.
 import json
 import os
 import shlex
+import subprocess
 import sys
 
+from PyQt6.QtCore import QLockFile
 from PyQt6.QtNetwork import QLocalSocket
 
 from . import integrate
+from . import paths
 
 SERVER_NAME = "dikte-" + (
     str(os.getuid()) if hasattr(os, "getuid")
@@ -54,10 +57,9 @@ def launcher():
     if not getattr(sys, "frozen", False):
         return [sys.executable, script_path()]
     if sys.platform == "win32":
-        windowed = os.path.join(os.path.dirname(sys.executable),
+        windowed = integrate.windowed_executable()
-                                integrate.WINDOWS_APP)
+        if windowed is not None:
-        if os.path.isfile(windowed):
+            return [str(windowed)]
-            return [windowed]
     return [os.environ.get("APPIMAGE") or sys.executable]
 
 
@@ -72,6 +74,60 @@ def command_for(verb):
     return shlex.join(launcher() + ([verb] if verb else []))
 
 
+def already_serving():
+    """Whether a running instance answers on this user's name.
+
+    Asked before an instance opens a server of its own, because listen() is
+    not the check: a Windows named pipe takes a second server on the same name
+    rather than refusing it, and everywhere else removeServer() would first
+    take the live socket away from the instance holding it. Either way two
+    whole Diktes then run, and the newer one's sweep() kills the whisper the
+    older one is answering dictations with. The probe is "status" and nothing
+    else: a verb with a side effect here would fire it during the relaunch a
+    slow-to-answer instance provokes, on top of the verb being forwarded.
+    """
+    return send("status") is not None
+
+
+def instance_lock():
+    """This user's one-Dikte lock, taken before anything else is built.
+
+    The probe above has a hole: two copies started in the same moment both ask
+    before either listens, and both come up. A lock file closes it, and
+    QLockFile writes the holder's pid into it, so a lock a killed instance
+    left behind identifies itself as stale and clears. None when the data
+    directory cannot be made, which a start should survive: the probe still
+    stands guard, just without the simultaneous-start case.
+    """
+    try:
+        paths.DATA_DIR.mkdir(parents=True, exist_ok=True)
+    except OSError:
+        return None
+    lock = QLockFile(str(paths.DATA_DIR / "dikte.lock"))
+    # Never presume a lock is stale by age alone; the pid check is the truth.
+    lock.setStaleLockTime(0)
+    return lock
+
+
+def respawn(arguments):
+    """Start this installation again with `arguments`, leaving this process.
+
+    execv everywhere it works the way it says: the new process takes this
+    pid and nothing is left behind. On Windows execv mangles arguments with
+    spaces and leaves the two processes sharing a console, so the replacement
+    is started detached instead and the caller exits on its own.
+    """
+    args = launcher() + list(arguments)
+    if sys.platform == "win32":
+        # By value where the names are missing, so the Windows half of this is
+        # testable from the suite's other platforms too.
+        detached = (getattr(subprocess, "DETACHED_PROCESS", 0x00000008)
+                    | getattr(subprocess, "CREATE_NEW_PROCESS_GROUP", 0x00000200))
+        subprocess.Popen(args, creationflags=detached, close_fds=True)
+        return
+    os.execv(args[0], args)
+
+
 def send(cmd, wait=False, timeout=0, **args):
     """Send one request; the reply, or None when no instance is running.
 

install.ps1

@@ -23,9 +23,20 @@ $autostartLink = Join-Path $startup "Dikte.lnk"
 $cmdShim = Join-Path $env:LOCALAPPDATA "Microsoft\WindowsApps\dikte.cmd"
 
 if ($Uninstall) {
-    foreach ($path in @($shortcut, $autostartLink, $cmdShim)) {
+    foreach ($path in @($shortcut, $autostartLink)) {
         if (Test-Path $path) { Remove-Item $path -Force; Write-Host "removed: $path" }
     }
+    # The packaged install writes the same shim, naming its own dikte-cli.exe.
+    # Only the one naming this checkout is ours to delete; taking the other
+    # would break the `dikte` command of an install this script never made.
+    if (Test-Path $cmdShim) {
+        if ((Get-Content $cmdShim -Raw).Contains($entry)) {
+            Remove-Item $cmdShim -Force
+            Write-Host "removed: $cmdShim"
+        } else {
+            Write-Host "left alone: $cmdShim (it names another install, not this checkout)"
+        }
+    }
     Write-Host "Dikte's shortcuts are gone. The repository and your settings are not."
     exit 0
 }
@@ -65,6 +76,15 @@ foreach ($path in @($shortcut) + $(if ($Autostart) { @($autostartLink) } else {
     Write-Host "shortcut: $path"
 }
 
+if ($Autostart) {
+    # The packaged build keeps its sign-in entry in the registry. Left there
+    # beside the shortcut written above, both would start a Dikte at sign-in,
+    # and this install is the one being asked for.
+    Remove-ItemProperty -Path "HKCU:\Software\Microsoft\Windows\CurrentVersion\Run" `
+        -Name "Dikte" -ErrorAction SilentlyContinue
+    Write-Host "autostart: the Startup shortcut replaces any registry Run entry a packaged install left"
+}
+
 # --- the dikte command ------------------------------------------------------
 # The interpreter by its full path rather than by name: the one checked above is
 # the one the command line should run, whatever a later PATH change puts first.

packaging/dikte.iss

@@ -59,6 +59,13 @@ Name: "autostart"; Description: "Start Dikte when I sign in"
 [Files]
 Source: "{#Source}\*"; DestDir: "{app}"; Flags: recursesubdirs ignoreversion
 
+[InstallDelete]
+; A checkout's install.ps1 -Autostart is a shortcut in the Startup folder. The
+; registry entry this setup writes replaces it, and both left in place would be
+; two Diktes at every sign-in. Only under the autostart task: somebody who
+; unticked the box has not asked for their checkout's entry to go.
+Type: files; Name: "{userstartup}\Dikte.lnk"; Tasks: autostart
+
 [Icons]
 Name: "{autoprograms}\Dikte"; Filename: "{app}\Dikte.exe"
 
@@ -111,7 +118,14 @@ begin
 end;
 
 procedure CurUninstallStepChanged(CurUninstallStep: TUninstallStep);
+var
+  Shim: AnsiString;
 begin
+  { Only the shim this setup wrote, which is the one naming its dikte-cli.exe.
+    install.ps1 writes the same file for a checkout, naming that checkout's
+    Python, and a shim somebody else wrote is not this uninstaller's to take. }
   if CurUninstallStep = usUninstall then
-    DeleteFile(ShimPath());
+    if LoadStringFromFile(ShimPath(), Shim)
+       and (Pos(ExpandConstant('{app}\dikte-cli.exe'), Shim) > 0) then
+      DeleteFile(ShimPath());
 end;

tests/test_integrate.py

@@ -475,6 +475,17 @@ class Windows(unittest.TestCase):
         self.installed = pathlib.Path(self.tmp.name).resolve()
         self.app = self.installed / "Dikte.exe"
         self.app.write_text("")
+        # APPDATA pointed into the sandbox, so that the Startup folder these
+        # tests delete from is never the machine's own.
+        appdata = mock.patch.dict(os.environ,
+                                  {"APPDATA": str(self.installed / "Roaming")})
+        appdata.start()
+        self.addCleanup(appdata.stop)
+
+    def startup_shortcut(self):
+        """Where install.ps1 -Autostart puts a checkout's sign-in entry."""
+        return (self.installed / "Roaming" / "Microsoft" / "Windows"
+                / "Start Menu" / "Programs" / "Startup" / "Dikte.lnk")
 
     def _write(self, command):
         self.value = command
@@ -510,6 +521,45 @@ class Windows(unittest.TestCase):
         self.assertEqual(len(self.install()), 1)
         self.assertEqual(self.value, f'"{self.app}"')
 
+    def test_an_entry_for_another_working_install_is_left_alone(self):
+        """The same courtesy the Linux half pays another menu entry: an entry
+        naming an executable that still exists is an installation that still
+        works, and a start of this one has no business redirecting it."""
+        other = self.installed / "Elsewhere" / "Dikte.exe"
+        other.parent.mkdir()
+        other.write_text("")
+        self.value = f'"{other}"'
+        self.assertEqual(self.install(), [])
+        self.assertEqual(self.value, f'"{other}"')
+
+    def test_asking_outright_overrules_a_working_other_install(self):
+        other = self.installed / "Elsewhere" / "Dikte.exe"
+        other.parent.mkdir()
+        other.write_text("")
+        self.value = f'"{other}"'
+        self.assertEqual(self.install(force=True), [integrate._run_entry_name()])
+        self.assertEqual(self.value, f'"{self.app}"')
+
+    def test_typing_it_sweeps_away_a_checkout_startup_shortcut(self):
+        """install.ps1 -Autostart writes it, the Run value replaces it, and
+        both left in place would be two Diktes at every sign-in."""
+        shortcut = self.startup_shortcut()
+        shortcut.parent.mkdir(parents=True)
+        shortcut.write_text("")
+        changed = self.install(force=True)
+        self.assertIn(shortcut, changed)
+        self.assertFalse(shortcut.exists())
+
+    def test_a_start_leaves_a_checkout_startup_shortcut_alone(self):
+        """The silent call on every start has not been asked to move the
+        machine off its checkout."""
+        shortcut = self.startup_shortcut()
+        shortcut.parent.mkdir(parents=True)
+        shortcut.write_text("")
+        self.value = f'"{self.app}"'
+        self.assertEqual(self.install(), [])
+        self.assertTrue(shortcut.exists())
+
     def test_running_it_again_changes_nothing(self):
         self.install(force=True)
         self.assertEqual(self.install(), [])
@@ -521,6 +571,31 @@ class Windows(unittest.TestCase):
         self.assertEqual(self.remove(), [])
 
 
+class WindowedExecutable(unittest.TestCase):
+    """The windowed executable, looked up beside whichever one is running.
+
+    Beside rather than at a known place: the setup lays both executables into
+    one directory wherever that directory was put, so either can find the
+    other without knowing where the install is.
+    """
+
+    def setUp(self):
+        self.tmp = tempfile.TemporaryDirectory()
+        self.addCleanup(self.tmp.cleanup)
+        self.installed = pathlib.Path(self.tmp.name).resolve()
+
+    def test_found_beside_the_named_executable(self):
+        windowed = self.installed / "Dikte.exe"
+        windowed.write_text("")
+        self.assertEqual(
+            integrate.windowed_executable(str(self.installed / "dikte-cli.exe")),
+            windowed)
+
+    def test_none_when_no_setup_installed_one(self):
+        self.assertIsNone(
+            integrate.windowed_executable(str(self.installed / "dikte-cli.exe")))
+
+
 class WindowsExecutableNames(unittest.TestCase):
     """The two Windows executables, read out of the files that name them.
 

tests/test_ipc.py

@@ -14,6 +14,7 @@ import unittest
 from unittest import mock
 
 from dikte import ipc
+from tests.support import DikteTest
 
 
 class FakeSocket:
@@ -185,5 +186,74 @@ class Send(unittest.TestCase):
         self.assertTrue(sock.disconnected)
 
 
+class AlreadyServing(unittest.TestCase):
+    """The single-instance check, which listen() cannot be: a Windows pipe
+    takes a second server on the same name rather than refusing it."""
+
+    def probe(self, socket):
+        with mock.patch.object(ipc, "QLocalSocket", return_value=socket):
+            return ipc.already_serving()
+
+    def test_nothing_running_means_go_ahead(self):
+        self.assertFalse(self.probe(FakeSocket(connected=False)))
+
+    def test_an_answer_means_yield(self):
+        self.assertTrue(self.probe(FakeSocket(reply=b'{"ok": true}\n')))
+
+    def test_the_probe_has_no_side_effect(self):
+        """A probe that opened a window would open it during the relaunch a
+        slow instance provokes, on top of the verb being forwarded."""
+        sock = FakeSocket(reply=b'{"ok": true}\n')
+        self.probe(sock)
+        self.assertEqual(sock.written.decode("utf-8").strip(), "status")
+
+    def test_an_instance_too_old_to_answer_still_counts_as_running(self):
+        self.assertTrue(self.probe(FakeSocket(reply=b"")))
+
+
+class InstanceLock(DikteTest):
+    def setUp(self):
+        super().setUp()
+        # The lock derives its home from paths, which DikteTest's cfg patches
+        # do not cover; without this the test would write into the real one.
+        from dikte import paths
+        self.patch_attr(paths, "DATA_DIR", self.path("data"))
+
+    def test_one_holder_at_a_time(self):
+        first = ipc.instance_lock()
+        self.assertIsNotNone(first)
+        self.assertTrue(first.tryLock(0))
+        second = ipc.instance_lock()
+        self.assertFalse(second.tryLock(0))
+        first.unlock()
+        self.assertTrue(second.tryLock(0))
+        second.unlock()
+
+    def test_the_lock_lives_in_the_data_directory(self):
+        from dikte import paths
+        lock = ipc.instance_lock()
+        self.assertTrue(lock.tryLock(0))
+        self.assertTrue((paths.DATA_DIR / "dikte.lock").exists())
+        lock.unlock()
+
+
+class Respawn(unittest.TestCase):
+    def test_windows_starts_a_detached_process_and_returns(self):
+        with mock.patch.object(sys, "platform", "win32"), \
+                mock.patch.object(ipc, "launcher", return_value=["py", "x"]), \
+                mock.patch.object(ipc.subprocess, "Popen") as popen:
+            ipc.respawn(["--gui"])
+        self.assertEqual(popen.call_args.args[0], ["py", "x", "--gui"])
+        self.assertEqual(popen.call_args.kwargs["creationflags"],
+                         0x00000008 | 0x00000200)
+
+    def test_everywhere_else_the_process_is_replaced(self):
+        with mock.patch.object(sys, "platform", "linux"), \
+                mock.patch.object(ipc, "launcher", return_value=["py", "x"]), \
+                mock.patch.object(ipc.os, "execv") as execv:
+            ipc.respawn(["toggle", "--gui"])
+        execv.assert_called_once_with("py", ["py", "x", "toggle", "--gui"])
+
+
 if __name__ == "__main__":
     unittest.main()