fix(dashboard): keep the '-' placeholder on failed /browse reads instead of '[redacted]'

src/ZB.MOM.WW.MxGateway.Server/Dashboard/DashboardLiveDataService.cs

@@ -53,9 +53,12 @@ public sealed class DashboardLiveDataService : IDashboardLiveDataService, IAsync
     /// <summary>
     ///     <c>MxGateway:Dashboard:ShowTagValues</c>. False (the default)
     ///     substitutes <see cref="DashboardTagValue.RedactedValueText"/> for every
-    ///     value this service hands the Browse panel; quality, data type, source
-    ///     timestamp, and any error still describe the real read, so the panel
-    ///     remains a diagnostic surface without being a value-disclosure one.
+    ///     successfully read value this service hands the Browse panel; quality,
+    ///     data type, source timestamp, and any error still describe the real
+    ///     read, so the panel remains a diagnostic surface without being a
+    ///     value-disclosure one. Failed reads keep their existing "-" placeholder:
+    ///     there was no value to suppress, so claiming one was withheld would
+    ///     misreport the failure.
     /// </summary>
     private readonly bool _showTagValues;
 
@@ -124,9 +127,17 @@ public sealed class DashboardLiveDataService : IDashboardLiveDataService, IAsync
             // The only place the /browse live-value gate is evaluated: the page
             // renders whatever ValueText it is handed, so a second check in the
             // view could only ever disagree with this one.
+            //
+            // A failed read is left alone: it has no value to suppress, and its
+            // ValueText is already the "-" placeholder. Substituting "[redacted]"
+            // there would tell the operator a value was withheld when the read
+            // never produced one — the Error column says why it failed, and the
+            // two must not contradict each other.
             DashboardTagValue[] values = results
                 .Select(DashboardTagValue.FromBulkReadResult)
-                .Select(value => _showTagValues ? value : value with { ValueText = DashboardTagValue.RedactedValueText })
+                .Select(value => _showTagValues || !value.Ok
+                    ? value
+                    : value with { ValueText = DashboardTagValue.RedactedValueText })
                 .ToArray();
             return new DashboardLiveReadResult(values, null, session.SessionId, session.WorkerProcessId);
         }

src/ZB.MOM.WW.MxGateway.Tests/Gateway/Dashboard/DashboardLiveDataServiceTests.cs

@@ -237,6 +237,38 @@ public sealed class DashboardLiveDataServiceTests
         Assert.Equal("Double", value.DataType);
     }
 
+    /// <summary>
+    /// Verifies redaction is scoped to reads that actually produced a value: a
+    /// failed read keeps the "-" placeholder rather than claiming a value was
+    /// withheld, and its diagnostic still reaches the panel. Redacting it would
+    /// contradict the error the same row displays.
+    /// </summary>
+    [Fact]
+    public async Task ReadAsync_WhenReadFailedAndShowTagValuesFalse_LeavesPlaceholderUnredacted()
+    {
+        RecordingWorkerClient worker = new()
+        {
+            ReadValue = new MxValue { DataType = MxDataType.Double, DoubleValue = 42.5 },
+        };
+        worker.FailReadFor.Add("Bad.PV");
+        await using FakeSessionManager sessionManager = new(worker);
+        await using DashboardLiveDataService service = CreateService(sessionManager, showTagValues: false);
+
+        DashboardLiveReadResult result = await service.ReadAsync(
+            ["Bad.PV", "Tank_001.PV"],
+            CancellationToken.None);
+
+        DashboardTagValue failed = result.Values.Single(value => value.TagAddress == "Bad.PV");
+        Assert.False(failed.Ok);
+        Assert.Equal("-", failed.ValueText);
+        Assert.Equal("Simulated read failure.", failed.Error);
+        Assert.False(failed.QualityGood);
+
+        // The successful row in the same read is still redacted.
+        DashboardTagValue succeeded = result.Values.Single(value => value.TagAddress == "Tank_001.PV");
+        Assert.Equal(DashboardTagValue.RedactedValueText, succeeded.ValueText);
+    }
+
     private static DashboardLiveDataService CreateService(
         ISessionManager sessionManager,
         bool showTagValues = false)
@@ -387,6 +419,9 @@ public sealed class DashboardLiveDataServiceTests
         /// </summary>
         public MxValue? ReadValue { get; set; }
 
+        /// <summary>Gets the tag addresses whose bulk read comes back unsuccessful.</summary>
+        public HashSet<string> FailReadFor { get; } = new(StringComparer.OrdinalIgnoreCase);
+
         /// <summary>Gets the item handle bound for a previously subscribed tag.</summary>
         /// <param name="tagAddress">Tag address to look up.</param>
         /// <returns>The bound item handle.</returns>
@@ -499,6 +534,20 @@ public sealed class DashboardLiveDataServiceTests
             BulkReadReply readReply = new();
             foreach (string tagAddress in tagAddresses)
             {
+                if (FailReadFor.Contains(tagAddress))
+                {
+                    readReply.Results.Add(new BulkReadResult
+                    {
+                        ServerHandle = RegisteredServerHandle,
+                        TagAddress = tagAddress,
+                        ItemHandle = _itemHandles.TryGetValue(tagAddress, out int failedHandle) ? failedHandle : 0,
+                        WasSuccessful = false,
+                        Quality = 0,
+                        ErrorMessage = "Simulated read failure.",
+                    });
+                    continue;
+                }
+
                 BulkReadResult readResult = new()
                 {
                     ServerHandle = RegisteredServerHandle,