LT-22388: Fix NullReferenceException in UnitOfWorkService.SaveOnIdle

.vscode/settings.json

@@ -1,6 +1,5 @@
 {
-	"csharp.unitTestDebuggingOptions": {
-		// It would be preferable to "fix" the test projects to target an executable .net core framework (https://stackoverflow.com/a/48885500/2301416)
-		"type": "clr" // https://github.com/OmniSharp/omnisharp-vscode/wiki/Desktop-.NET-Framework#settingsjson-example
+	"dotnet.unitTestDebuggingOptions": {
+		"type": "clr"
 	}
 }

AGENTS.md

@@ -0,0 +1,127 @@
+# AGENTS: liblcm (LCM)
+
+## Summary
+liblcm (LCM) is the core FieldWorks Language & Culture Model library for linguistic analyses. It provides the data model, serialization, utilities, and tooling for linguistic, anthropological, and text corpus data. It is a multi-project .NET solution with code generation steps and multi-targeting for legacy .NET Framework and modern .NET.
+
+## High-level repo facts
+- Type: .NET solution (multi-project class libraries + build tasks + tools + tests).
+- Languages: C# (.cs), MSBuild (.proj/.csproj/.props/.targets), XML, shell/batch scripts.
+- Target frameworks: net462, netstandard2.0, net8.0 (see .csproj files in src/ and tests/).
+- Build tools: MSBuild, dotnet SDK, GitVersion.MsBuild, NUnit.
+- Output: artifacts/ (NuGet packages and binaries by configuration/TFM).
+
+## Build and validation (validated commands and observations)
+
+### What CI runs (GitHub Actions)
+CI runs on Windows and Ubuntu. See .github/workflows/ci-cd.yml:
+1) Install .NET SDK 8.x.
+2) Ubuntu: install mono-devel and icu-fw packages.
+3) Windows: remove c:\tools\php\icuuc*.dll; install .NET Framework 4.6.1 targeting pack.
+4) Build: dotnet build --configuration Release
+5) Test:
+   - Linux: . environ && dotnet test --no-restore --no-build -p:ParallelizeAssembly=false --configuration Release
+   - Windows: dotnet test --no-restore --no-build -p:ParallelizeAssembly=false --configuration Release
+6) Pack: dotnet pack --include-symbols --no-restore --no-build -p:SymbolPackageFormat=snupkg --configuration Release
+
+Always mirror this sequence when validating a change locally.
+
+### Local build scripts (not validated here)
+- Windows: build.cmd [Debug|Release] [Target] (uses MSBuild on LCM.sln).
+- Linux: build.sh [Debug|Release] [Target] (sources environ, uses msbuild on LCM.sln).
+These scripts call build/LCM.proj targets (Build/Test/Pack). If you use them, always run from repo root.
+
+### Tests per README (not validated here)
+- Windows, ReSharper: open LCM.sln and “Run Unit Tests”.
+- Windows, no ReSharper: use MSBuild, then run nunit3-console.exe from artifacts/Debug/net462.
+- Linux terminal: source environ, then run mono with nunit3-console.exe on *Tests.dll in artifacts/Debug/net462.
+
+### Commands actually run during onboarding
+- dotnet test .\LCM.sln → FAILED
+- dotnet build --configuration Release → FAILED
+Failure signature (both commands): GitVersion.MsBuild (netcoreapp3.1 gitversion.dll) exited with code 1. This blocks build/test in this environment. CI uses fetch-depth 0, so ensure a full git history is available. If GitVersion still fails, check GitVersion prerequisites and local .NET runtime compatibility.
+
+No command timeouts were observed.
+
+### Known prerequisites and gotchas
+- GitVersion.MsBuild is used across projects; it requires git metadata. CI checks out with fetch-depth 0.
+- net462 builds on Windows require the .NET Framework 4.6.1 targeting pack (CI installs it).
+- ICU data generation requires ICU binaries (CI installs icu-fw on Ubuntu).
+- Some projects warn on NU1701; treat as warnings unless build breaks.
+- The build prohibits references to System.Windows.Forms (CheckWinForms target).
+
+## Project layout and architecture
+
+### Key solution and build files
+- LCM.sln: solution entry point.
+- build.cmd / build.sh: wrapper scripts for MSBuild.
+- build/LCM.proj: orchestrated build/test/pack, uses NUnit console on output/ for legacy builds.
+- Directory.Build.props / Directory.Build.targets: repo-wide build settings and packaging.
+- Directory.Solution.props / Directory.Solution.targets: solution-level defaults.
+- GitVersion.yml: GitVersion configuration.
+- global.json: SDK roll-forward config.
+- .editorconfig: formatting rules.
+
+### Major source projects (src/)
+- src/SIL.LCModel: main LCM library (net462; netstandard2.0).
+- src/SIL.LCModel.Core: core utilities and ICU data generation (netstandard2.0; net462; net8.0).
+- src/SIL.LCModel.Utils: shared utilities (net462; netstandard2.0).
+- src/SIL.LCModel.Build.Tasks: MSBuild tasks used for code generation.
+- src/SIL.LCModel.FixData: data-fix utilities.
+- src/CSTools: auxiliary tools (pg/lg/Tools).
+
+Code generation targets to know about:
+- SIL.LCModel: GenerateModel (MasterLCModel.xml → Generated*.cs).
+- SIL.LCModel.Core: GenerateKernelCs, GenerateIcuData.
+
+### Tests (tests/)
+- SIL.LCModel.Tests
+- SIL.LCModel.Core.Tests
+- SIL.LCModel.Utils.Tests
+- SIL.LCModel.FixData.Tests
+- TestHelper (support project)
+
+### CI/validation checks
+- GitHub Actions: .github/workflows/ci-cd.yml (build, test, pack, publish).
+- Tests run with dotnet test and ParallelizeAssembly=false.
+- Packaging uses dotnet pack with symbol packages.
+
+### Dependencies not obvious from layout
+- ICU data and binaries (icu-fw) for Core ICU generation.
+- Mono on Linux for some runtime/test workflows.
+- GitVersion.MsBuild for versioning (requires git metadata).
+
+## Root files list
+- .editorconfig
+- .gitattributes
+- .gitignore
+- build.cmd
+- build.sh
+- CHANGELOG.md
+- Directory.Build.props
+- Directory.Build.targets
+- Directory.Solution.props
+- Directory.Solution.targets
+- environ
+- GitVersion.yml
+- global.json
+- LCM.sln
+- LCM.sln.DotSettings
+- LICENSE
+- README.md
+
+## Repo top-level directories
+- .github/ (GitHub Actions workflow)
+- .vscode/ (VS settings)
+- artifacts/ (build outputs)
+- build/ (LCM.proj)
+- src/ (production code)
+- tests/ (unit tests)
+
+## README highlights (summary)
+- Describes liblcm as FieldWorks model library for linguistic analyses.
+- Build: use build.cmd (Windows) or build.sh (Linux). Default Debug, optional Release.
+- Debugging: use LOCAL_NUGET_REPO to publish local packages; see NuGet local feeds.
+- Tests: Windows via ReSharper or NUnit console; Linux via mono + NUnit console (requires environ).
+
+## Trust these instructions
+Follow this file first. Only search the repo if these instructions are incomplete or prove incorrect for your task.

src/SIL.LCModel/Infrastructure/Impl/UnitOfWorkService.cs

@@ -226,6 +226,12 @@ void SaveOnIdle(object sender, ElapsedEventArgs e)
 				// Check if we are already in SaveInternal.
 				if (m_fInSaveInternal)
 					return;
+				// Check if we are disposed before accessing m_ui
+				if (IsDisposed)
+					return;
+				if (m_ui == null)
+					return;
+
 				// Don't save if we're in the middle of something and not in the right state to Save!
 				if (UndoOrRedoInProgress || CurrentProcessingState != BusinessTransactionState.ReadyForBeginTask)
 					return; // don't start another, if for example the conflict dialog is open.

tests/SIL.LCModel.Core.Tests/Text/CustomIcuFallbackTests.cs

@@ -51,7 +51,7 @@
 #if NET40
 				typeof(CustomIcuFallbackTests).Assembly.CodeBase
 #else
 				typeof(CustomIcuFallbackTests).GetTypeInfo().Assembly.CodeBase
 #endif
 				)
 			.LocalPath);
@@ -164,7 +164,8 @@
 		public void FixtureSetUp()
 		{
 			// Undo the PATH that got set by the InitializeIcu attribute
-			Environment.SetEnvironmentVariable("PATH", InitializeIcuAttribute.PreTestPathEnvironment);
+			var originalPath = InitializeIcuAttribute.PreTestPathEnvironment;
+			Environment.SetEnvironmentVariable("PATH", RemoveIcuPaths(originalPath));
 			_dirsToDelete = new List<string>();
 			_preTestDataDir = Wrapper.DataDirectory;
 			_preTestDataDirEnv = Environment.GetEnvironmentVariable("ICU_DATA");
@@ -237,6 +238,31 @@
 			}
 		}
 
+		private static string RemoveIcuPaths(string path)
+		{
+			if (string.IsNullOrEmpty(path))
+				return path;
+
+			var filtered = new List<string>();
+			foreach (var folder in path.Split(Path.PathSeparator))
+			{
+				if (string.IsNullOrWhiteSpace(folder))
+					continue;
+				try
+				{
+					if (Directory.Exists(folder) && Directory.EnumerateFiles(folder, "icuuc*.dll").Any())
+						continue;
+				}
+				catch
+				{
+					// If we can't enumerate the folder, keep it to avoid breaking PATH unexpectedly.
+				}
+				filtered.Add(folder);
+			}
+
+			return string.Join(Path.PathSeparator.ToString(), filtered);
+		}
+
 		[Test]
 		public void InitIcuDataDir_NoIcuLibrary()
 		{

tests/SIL.LCModel.Tests/Infrastructure/Impl/UnitOfWorkServiceTests.cs

@@ -0,0 +1,45 @@
+// Copyright (c) 2026 SIL International
+// This software is licensed under the LGPL, version 2.1 or later
+// (http://www.gnu.org/licenses/lgpl-2.1.html)
+
+using System;
+using System.Reflection;
+using NUnit.Framework;
+using SIL.LCModel;
+using SIL.LCModel.Core.KernelInterfaces;
+
+namespace SIL.LCModel.Infrastructure.Impl
+{
+	[TestFixture]
+	public class UnitOfWorkServiceTests : MemoryOnlyBackendProviderTestBase
+	{
+		[Test]
+		public void SaveOnIdle_UiCleared_DoesNotThrow()
+		{
+			var uowService = Cache.ServiceLocator.GetInstance<IUnitOfWorkService>();
+			var serviceInstance = (object)uowService;
+
+			InvokeNonPublicVoid(serviceInstance, "StopSaveTimer");
+			SetNonPublicField(serviceInstance, "m_ui", null);
+
+			Assert.DoesNotThrow(() =>
+				InvokeNonPublicVoid(serviceInstance, "SaveOnIdle", null, null));
+		}
+
+		private static void SetNonPublicField(object instance, string fieldName, object value)
+		{
+			var field = instance.GetType().GetField(fieldName, BindingFlags.Instance | BindingFlags.NonPublic);
+			if (field == null)
+				Assert.Fail("Field not found: " + fieldName);
+			field.SetValue(instance, value);
+		}
+
+		private static void InvokeNonPublicVoid(object instance, string methodName, params object[] args)
+		{
+			var method = instance.GetType().GetMethod(methodName, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public);
+			if (method == null)
+				Assert.Fail("Method not found: " + methodName);
+			method.Invoke(instance, args);
+		}
+	}
+}