fix(worker): narrow AlarmAckWriter ArgumentException interop filter

Resolve the operator user, password and comment before the interop try
blocks, and match ArgumentException as an MXAccess failure only when it
carries E_INVALIDARG and is not ArgumentNullException or
ArgumentOutOfRangeException. A programming error inside the try blocks
now propagates instead of being reported as an authentication or write
failure.

Fixes #164

Claude-Session: https://claude.ai/code/session_016J6isfcgqy4SB2RK3ZvFvT

docs/Grpc.md

@@ -115,7 +115,7 @@ The worker calls `AuthenticateUser` as the operator, then writes `operator_comme
 | `AuthenticateUser` failed with a server-gone HRESULT (`RPC_E_DISCONNECTED`, `RPC_S_SERVER_UNAVAILABLE`, `RPC_E_SERVERFAULT`); the writer tears down its MXAccess registration and re-registers on the next ack | `MXACCESS_FAILURE` | that HRESULT |
 | `AddItem`, `Advise` or `Write` on the `AckMsg` item raised an MXAccess error (`COMException`, or `ArgumentException` for `E_INVALIDARG`); the item is dropped and re-added on the next ack, and a server-gone HRESULT also tears down the registration | `MXACCESS_FAILURE` | the exception's HRESULT |
 | Write rejected (`OnWriteComplete` non-OK) | `MXACCESS_FAILURE` | the `detail` of the `OnWriteComplete` `MXSTATUS_PROXY`, or `-1` when `detail` is `0` |
-| Any other exception escaping the ack (e.g. the ack writer's MXAccess `Register` failing, or the monitor's worker session having no active alarm subscription — `InvalidOperationException`) | `MXACCESS_FAILURE` | the exception's `HResult`; the diagnostic names only the exception type and HRESULT |
+| Any other exception escaping the ack (e.g. the ack writer's MXAccess `Register` failing, the monitor's worker session having no active alarm subscription — `InvalidOperationException` — or an argument error that is not the interop's `E_INVALIDARG`: `ArgumentNullException`, `ArgumentOutOfRangeException`, or an `ArgumentException` with another HRESULT, which signal a bug rather than an MXAccess failure) | `MXACCESS_FAILURE` | the exception's `HResult`; the diagnostic names only the exception type and HRESULT |
 
 `reply.Statuses` carries the `OnWriteComplete` `MxStatusProxy` rows when they were observed. Because an unconfirmed write also returns `OK`, a client that must be certain should watch for the resulting transition on `StreamAlarms`. `AcknowledgeAlarm` stays under the `invoke:write` scope; see [Authorization](./Authorization.md).
 

src/ZB.MOM.WW.MxGateway.Worker.Tests/MxAccess/AlarmAckWriterTests.cs

@@ -187,6 +187,70 @@ public sealed class AlarmAckWriterTests
         Assert.DoesNotContain("Unregister", server.Operations);
     }
 
+    [Fact]
+    public void Acknowledge_WhenAuthenticateUserThrowsArgumentExceptionWithEInvalidArg_ReturnsAuthenticationFailed()
+    {
+        // The HRESULT is what the narrowed filter keys on; set it explicitly so the
+        // test does not depend on ArgumentException's default HResult.
+        RecordingAckServer server = new RecordingAckServer
+        {
+            AuthenticateResult = 5,
+            AuthenticateException = new HResultArgumentException("bad credentials", unchecked((int)0x80070057)),
+        };
+        using AlarmAckWriter writer = new AlarmAckWriter(server, new MxAccessWriteCompletionCache(), () => { }, TimeSpan.FromMilliseconds(10), "MxGateway");
+
+        AlarmAckResult result = writer.Acknowledge("T.A.AckMsg", "one", Alice());
+
+        Assert.Equal(AlarmAckOutcome.AuthenticationFailed, result.Outcome);
+        Assert.Equal(unchecked((int)0x80070057), result.NativeStatus);
+    }
+
+    [Fact]
+    public void Acknowledge_WhenAuthenticateUserThrowsArgumentNullException_Propagates()
+    {
+        // A programming error is a bug, not an operator authentication failure.
+        RecordingAckServer server = new RecordingAckServer
+        {
+            AuthenticateResult = 5,
+            AuthenticateException = new ArgumentNullException("verifyUser"),
+        };
+        using AlarmAckWriter writer = new AlarmAckWriter(server, new MxAccessWriteCompletionCache(), () => { }, TimeSpan.FromMilliseconds(10), "MxGateway");
+
+        Assert.Throws<ArgumentNullException>(() => writer.Acknowledge("T.A.AckMsg", "one", Alice()));
+    }
+
+    [Fact]
+    public void Acknowledge_WhenAuthenticateUserThrowsArgumentExceptionWithOtherHResult_Propagates()
+    {
+        RecordingAckServer server = new RecordingAckServer
+        {
+            AuthenticateResult = 5,
+            AuthenticateException = new HResultArgumentException("not interop", unchecked((int)0x80131500)),
+        };
+        using AlarmAckWriter writer = new AlarmAckWriter(server, new MxAccessWriteCompletionCache(), () => { }, TimeSpan.FromMilliseconds(10), "MxGateway");
+
+        Assert.Throws<HResultArgumentException>(() => writer.Acknowledge("T.A.AckMsg", "one", Alice()));
+    }
+
+    [Fact]
+    public void Acknowledge_WhenWriteThrowsArgumentOutOfRangeException_Propagates()
+    {
+        RecordingAckServer server = new RecordingAckServer { AuthenticateResult = 5, WriteException = new ArgumentOutOfRangeException("value") };
+        using AlarmAckWriter writer = new AlarmAckWriter(server, new MxAccessWriteCompletionCache(), () => { }, TimeSpan.FromMilliseconds(10), "MxGateway");
+
+        Assert.Throws<ArgumentOutOfRangeException>(() => writer.Acknowledge("T.A.AckMsg", "one", Alice()));
+    }
+
+    [Fact]
+    public void Acknowledge_WhenOperatorUserNameIsNull_ThrowsBeforeAuthenticating()
+    {
+        RecordingAckServer server = new RecordingAckServer { AuthenticateResult = 5 };
+        using AlarmAckWriter writer = new AlarmAckWriter(server, new MxAccessWriteCompletionCache(), () => { }, TimeSpan.FromMilliseconds(10), "MxGateway");
+
+        Assert.Throws<ArgumentException>(() => writer.Acknowledge("T.A.AckMsg", "one", new AlarmAckOperator { UserName = null! }));
+        Assert.DoesNotContain(server.Operations, op => op.StartsWith("AuthenticateUser", StringComparison.Ordinal));
+    }
+
     [Fact]
     public void Acknowledge_WhenWriteThrowsArgumentException_RejectsAndDropsItem()
     {
@@ -290,6 +354,16 @@ public sealed class AlarmAckWriterTests
     }
 }
 
+/// <summary>ArgumentException with an explicit HRESULT (the setter is protected on net48).</summary>
+internal sealed class HResultArgumentException : ArgumentException
+{
+    public HResultArgumentException(string message, int hresult)
+        : base(message)
+    {
+        HResult = hresult;
+    }
+}
+
 internal sealed class RecordingAckServer : IMxAccessServer
 {
     private int nextItemHandle = 100;

src/ZB.MOM.WW.MxGateway.Worker/MxAccess/AlarmAckWriter.cs

@@ -34,6 +34,9 @@ public sealed class AlarmAckWriter : IAlarmAckWriter
     /// </summary>
     public const int DefaultMaxCachedItems = 256;
 
+    /// <summary>E_INVALIDARG, which the interop raises as ArgumentException.</summary>
+    private const int EInvalidArg = unchecked((int)0x80070057);
+
     private readonly IMxAccessComObjectFactory? factory;
     private readonly MxAccessWriteCompletionCache completionCache;
     private readonly Action pumpStep;
@@ -104,12 +107,20 @@ public sealed class AlarmAckWriter : IAlarmAckWriter
         if (string.IsNullOrWhiteSpace(itemAddress)) throw new ArgumentException("Ack item address is required.", nameof(itemAddress));
         if (ackOperator is null) throw new ArgumentNullException(nameof(ackOperator));
 
+        // Resolve every argument before the interop try blocks: their catch
+        // filters accept E_INVALIDARG ArgumentExceptions as MXAccess failures, so
+        // an argument error raised by this code must fail before reaching them.
+        if (ackOperator.UserName is null) throw new ArgumentException("Operator user name is required.", nameof(ackOperator));
+        string verifyUser = ackOperator.VerifyUser;
+        string password = ackOperator.Password ?? string.Empty;
+        string commentValue = comment ?? string.Empty;
+
         IMxAccessServer mx = EnsureRegistered();
 
         int userId;
         try
         {
-            userId = mx.AuthenticateUser(serverHandle, ackOperator.VerifyUser, ackOperator.Password ?? string.Empty);
+            userId = mx.AuthenticateUser(serverHandle, verifyUser, password);
         }
         catch (Exception ex) when (IsInteropFailure(ex))
         {
@@ -130,7 +141,7 @@ public sealed class AlarmAckWriter : IAlarmAckWriter
             return AlarmAckResult.Create(
                 AlarmAckOutcome.AuthenticationFailed,
                 ex.HResult,
-                $"Operator authentication failed for '{ackOperator.VerifyUser}' (HRESULT 0x{ex.HResult:X8}).");
+                $"Operator authentication failed for '{verifyUser}' (HRESULT 0x{ex.HResult:X8}).");
         }
 
         if (userId == 0)
@@ -138,7 +149,7 @@ public sealed class AlarmAckWriter : IAlarmAckWriter
             return AlarmAckResult.Create(
                 AlarmAckOutcome.AuthenticationFailed,
                 -1,
-                $"Operator authentication failed for '{ackOperator.VerifyUser}' (no user id returned).");
+                $"Operator authentication failed for '{verifyUser}' (no user id returned).");
         }
 
         ulong baselineVersion = 0;
@@ -177,7 +188,7 @@ public sealed class AlarmAckWriter : IAlarmAckWriter
             pumpStep();
             step = "Write";
             baselineVersion = completionCache.CurrentVersion(serverHandle, itemHandle);
-            mx.Write(serverHandle, itemHandle, comment ?? string.Empty, userId);
+            mx.Write(serverHandle, itemHandle, commentValue, userId);
         }
         catch (Exception ex) when (IsInteropFailure(ex))
         {
@@ -249,10 +260,23 @@ public sealed class AlarmAckWriter : IAlarmAckWriter
     ///     ArgumentException, E_ACCESSDENIED to UnauthorizedAccessException) and
     ///     the rest to COMException. Each carries the HRESULT in Exception.HResult.
     /// </summary>
+    /// <remarks>
+    ///     The ArgumentException arm exists because a wrong password or unknown
+    ///     user makes <c>AuthenticateUser</c> throw ArgumentException with
+    ///     E_INVALIDARG (0x80070057), observed live on windev on 2026-10-19. It
+    ///     is narrowed to that HRESULT, and excludes ArgumentNullException and
+    ///     ArgumentOutOfRangeException, so a programming error inside the try
+    ///     blocks propagates as a bug instead of being reported as an MXAccess
+    ///     authentication or write failure. The interop never raises those two
+    ///     subtypes for a COM HRESULT.
+    /// </remarks>
     private static bool IsInteropFailure(Exception ex) =>
         ex is ExternalException
-        || ex is ArgumentException
+        || ex is UnauthorizedAccessException
-        || ex is UnauthorizedAccessException;
+        || (ex is ArgumentException
+            && ex is not ArgumentNullException
+            && ex is not ArgumentOutOfRangeException
+            && ex.HResult == EInvalidArg);
 
     private static bool IsServerGone(int hresult) =>
         hresult == unchecked((int)0x80010108) // RPC_E_DISCONNECTED