Enable nullability and warnings-as-errors globally

[rolfbjarne]

Summary

Enable nullable reference types, treat-warnings-as-errors, and use the latest C# language version globally across the entire repository via Directory.Build.props.

Changes

Global settings (Directory.Build.props)

• Set <Nullable>enable</Nullable> globally.
• Set <TreatWarningsAsErrors>true</TreatWarningsAsErrors> globally.
• Set <LangVersion>latest</LangVersion> globally (when not already set).

Cleanup: remove per-project redundant settings

• Remove per-project <Nullable>enable</Nullable> from ~100+ .csproj files, since it's now set globally.
• Remove per-project <TreatWarningsAsErrors> and <WarningsAsErrors> settings that are now redundant.
• Remove per-project <LangVersion> settings that are now covered by the global default.

Fix nullability warnings in test code

• bindings-test: Fix nullability issues in ProtocolTest.cs, Registrar.cs, RuntimeTest.cs.
• dont-link: Fix nullability issues across multiple test files.
• link all: Fix nullability issues in link-all tests.
• link sdk: Fix nullability issues in link-sdk tests.
• BundledResources: Fix nullability in ResourcesTest.cs.
• F# tests: Fix nullability issues in F# test code.
• Other: Minor nullability fix in generate-frameworks-constants.cs.

🤖 Pull request created by Copilot

With this change, nullability is fully enabled everywhere, so:

• Fixes [Foundation] Missing nullability in some base types. #17285.
• Fixes Add C# 8 nullability annotations to bindings #6154.

[Copilot]

Pull request overview

This PR centralizes repository-wide compiler configuration by enabling nullable reference types, treating warnings as errors, and defaulting to the latest C# language version via Directory.Build.props, then cleans up per-project redundancy and adjusts test/sample code to compile cleanly under the stricter settings.

Changes:

• Enabled global <Nullable>enable</Nullable>, <TreatWarningsAsErrors>true</TreatWarningsAsErrors>, and default <LangVersion>latest</LangVersion> in Directory.Build.props.
• Removed now-redundant per-project Nullable / LangVersion / warnings-as-errors properties across tools, msbuild tasks, scripts, and test projects.
• Applied nullability-driven fixes across many test and sample sources (C# + F#), mostly by updating signatures, adding null checks, and adjusting reflection usage.

Reviewed changes

Copilot reviewed 147 out of 147 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
Directory.Build.props	Adds global Nullable/TreatWarningsAsErrors and default LangVersion.
tools/sharpie/Sharpie.Bind/Sharpie.Bind.csproj	Removes redundant LangVersion/Nullable.
tools/sharpie/Sharpie.Bind.Tool/Sharpie.Bind.Tool.csproj	Removes redundant LangVersion/Nullable.
tools/mtouch/mtouch.csproj	Removes redundant LangVersion/Nullable/TreatWarningsAsErrors.
tools/dotnet-linker/dotnet-linker.csproj	Removes redundant Nullable/TreatWarningsAsErrors.
tools/create-dotnet-linker-launch-json/create-dotnet-linker-launch-json.csproj	Removes redundant Nullable.
tools/class-redirector/class-redirector/class-redirector.csproj	Removes redundant Nullable.
tools/class-redirector/class-redirector-tests/class-redirector-tests.csproj	Removes redundant Nullable.
tests/xtro-sharpie/xtro-sharpie/xtro-sharpie.csproj	Removes redundant LangVersion/Nullable/WAE settings.
tests/xtro-sharpie/xtro-sanity/xtro-sanity.csproj	Removes redundant Nullable/WAE settings.
tests/xtro-sharpie/xtro-report/xtro-report.csproj	Removes redundant Nullable/WAE settings.
tests/xtro-sharpie/UnitTests/UnitTests.csproj	Removes redundant Nullable/WAE and drops an explicit System.Text.Json package ref.
tests/xtro-sharpie/u2todo/u2todo.csproj	Removes redundant Nullable.
tests/xtro-sharpie/u2ignore/u2ignore.csproj	Removes redundant Nullable.
tests/xharness/xharness.csproj	Removes redundant LangVersion/Nullable/WAE settings.
tests/xcframework-test/dotnet/tvOS/xcframework-test.csproj	Removes redundant LangVersion.
tests/xcframework-test/dotnet/shared.csproj	Removes redundant LangVersion/WAE settings.
tests/test-libraries/testgenerator.csproj	Removes redundant Nullable/LangVersion.
tests/test-libraries/custom-type-assembly/custom-type-assembly.csproj	Removes redundant LangVersion.
tests/sharpie/Sharpie.Bind.Tests/Sharpie.Bind.Tests.csproj	Removes redundant LangVersion/Nullable.
tests/rgen/Microsoft.Macios.Transformer.Tests/Microsoft.Macios.Transformer.Tests.csproj	Removes redundant Nullable and per-config TreatWarningsAsErrors.
tests/rgen/Microsoft.Macios.Generator.Tests/Microsoft.Macios.Generator.Tests.csproj	Removes redundant Nullable/TreatWarningsAsErrors.
tests/rgen/Microsoft.Macios.Bindings.CodeFixers.Tests/Microsoft.Macios.Bindings.CodeFixers.Tests.csproj	Removes redundant Nullable/LangVersion/TreatWarningsAsErrors.
tests/rgen/Microsoft.Macios.Bindings.Analyzer.Tests/Microsoft.Macios.Bindings.Analyzer.Tests.csproj	Removes redundant Nullable/TreatWarningsAsErrors.
tests/perftest/legacy/perftest-legacy.csproj	Removes redundant LangVersion.
tests/perftest/dotnet/perftest.csproj	Removes redundant LangVersion.
tests/mtouch/mtouchtests.csproj	Removes redundant LangVersion.
tests/msbuild/Xamarin.MacDev.Tests/Xamarin.MacDev.Tests.csproj	Removes redundant LangVersion/Nullable/WAE settings.
tests/msbuild/Xamarin.MacDev.Tests/TestHelpers/TestBase.cs	Adjusts APFS detection for nullable output handling.
tests/msbuild/Xamarin.MacDev.Tasks.Tests/Xamarin.MacDev.Tasks.Tests.csproj	Removes redundant LangVersion/Nullable/TreatWarningsAsErrors.
tests/monotouch-test/dotnet/shared.csproj	Removes redundant WAE settings.
tests/mmptest/mmptest.csproj	Removes redundant LangVersion.
tests/linker/trimmode link/dotnet/shared.csproj	Removes redundant WAE settings.
tests/linker/trimmode copy/dotnet/shared.csproj	Removes redundant WAE settings.
tests/linker/link sdk/ReflectionTest.cs	Nullability updates; adds null-forgiving to reflection chain.
tests/linker/link sdk/OptimizeGeneratedCodeTest.cs	Nullability updates; adds null-forgiving on UIFont creation.
tests/linker/link sdk/LocaleTest.cs	Makes local variable nullable to satisfy TryGetValue signature.
tests/linker/link sdk/LinkSdkRegressionTest.cs	Broad nullability fixes + additional guards/throws.
tests/linker/link sdk/LinkExtraDefsTest.cs	Adds null checks/throws around Type.GetType.
tests/linker/link sdk/dotnet/shared.csproj	Removes redundant WAE settings.
tests/linker/link sdk/DataContractTest.cs	Initializes property to avoid nullability warnings.
tests/linker/link sdk/CryptoTest.cs	Updates callback signatures and adds null guards.
tests/linker/link sdk/Bug1820Test.cs	Updates serializer fields and null-handling.
tests/linker/link sdk/BitcodeTest.cs	Adds null checks around reflection results.
tests/linker/link sdk/AotBugs.cs	Nullability annotations + constraints and guards.
tests/linker/link all/XmlSerializationTest.cs	Adjusts generics/nullable usage and adds null-forgiving on Deserialize.
tests/linker/link all/SerializationTest.cs	Changes Helper.GetType to use null-forgiving returns.
tests/linker/link all/SealerTest.cs	Adds null-forgiving to reflection calls.
tests/linker/link all/PreserveTest.cs	Initializes strings + adds null-forgiving to reflection calls.
tests/linker/link all/LinqExpressionTest.cs	Adds null-forgiving on GetConstructor.
tests/linker/link all/LinkAllTest.cs	Nullability tweaks (attributes, reflection, strings).
tests/linker/link all/LinkAllMacTest.cs	Adds null-forgiving on deserialized result usage.
tests/linker/link all/InternalsTest.cs	Adds nullability annotations and null-forgiving for PtrToString.
tests/linker/link all/InterfacesTest.cs	Uses null! return to satisfy non-nullable return type.
tests/linker/link all/dotnet/shared.csproj	Removes redundant WAE settings.
tests/linker/link all/DataContractTest.cs	Adds null-forgiving on ReadObject result.
tests/linker/link all/AttributeTest.cs	Adds null-forgiving on reflection results.
tests/linker/ILReader.cs	Marks operand nullable and adjusts string formatting/null handling.
tests/linker/dont link/TableViewSourceTest.cs	Adds null-forgiving to ToString() results.
tests/linker/dont link/dotnet/shared.csproj	Removes redundant WAE settings.
tests/linker/dont link/DontLinkRegressionTests.cs	Nullability tweaks in reflection invocation and assertion.
tests/linker/CommonLinkAnyTest.cs	Nullability tweaks for local/default parameter and ToString.
tests/linker/CommonLinkAllTest.cs	Nullability tweaks for Type.GetType + TypeConverterAttribute access.
tests/linker/BaseOptimizeGeneratedCodeTest.cs	Nullability tweaks + null-forgiving for delegate target and reflection.
tests/introspection/dotnet/shared.csproj	Removes redundant Nullable/WAE settings.
tests/introspection/ApiBaseTest.cs	Adds additional null-forgiving on Runner/Writer access.
tests/interdependent-binding-projects/dotnet/shared.csproj	Removes redundant WAE settings.
tests/EmbeddedResources/dotnet/shared.csproj	Removes redundant WAE settings.
tests/dotnet/UnitTests/ExtensionsTest.cs	Updates env dictionary value type to nullable.
tests/dotnet/UnitTests/DotNetUnitTests.csproj	Removes redundant Nullable/TreatWarningsAsErrors.
tests/dotnet/SizeTestApp/AppDelegate.cs	Nullability updates + CA1422 pragmas.
tests/dotnet/size-comparison/MySingleView/AppDelegate.cs	Nullability updates + CA1422 pragmas.
tests/dotnet/size-comparison/MauiForms/oldnet/MauiForms.iOS/AppDelegate.cs	Makes options parameter nullable.
tests/dotnet/MyTVApp/AppDelegate.cs	Makes Window property nullable.
tests/dotnet/MySingleView/AppDelegate.cs	Nullability updates + CA1422 pragmas.
tests/dotnet/MyRegistrarApp/AppDelegate.cs	Avoids direct cast from GCHandle.Target; throws only when exception present.
tests/dotnet/MyNativeAotAppWithTrimAnalysisWarning/shared.csproj	Opts out of global TreatWarningsAsErrors.
tests/dotnet/MyMauiApp/shared.csproj	Removes redundant Nullable.
tests/dotnet/MyMauiApp/MacCatalyst/App.xaml.cs	Switches to CreateWindow override for MAUI initialization.
tests/dotnet/MyMauiApp/iOS/App.xaml.cs	Switches to CreateWindow override for MAUI initialization.
tests/dotnet/MyInterpretedApp/AppDelegate.cs	Nullability updates + CA1422 pragmas.
tests/dotnet/MyCatalystApp/Main.cs	Uses typeof (AppDelegate) instead of string.
tests/dotnet/MyCatalystApp/AppDelegate.cs	Makes Window property nullable.
tests/dotnet/ExtensionProjectWithFrameworks/tvOS/ServiceProvider.cs	Adds CA1422 pragmas around tvOS API usage.
tests/dotnet/ExtensionProjectWithFrameworks/macOS/ShareViewController.cs	Adds null-propagation around ExtensionContext usage.
tests/dotnet/ExtensionProjectWithFrameworks/iOS/ShareViewController.cs	Uses null-propagation and empty array for CompleteRequest.
tests/dotnet/ExtensionProject/tvOS/ServiceProvider.cs	Adds CA1422 pragmas around tvOS API usage.
tests/dotnet/ExtensionProject/macOS/ShareViewController.cs	Adds null-propagation around ExtensionContext usage.
tests/dotnet/ExtensionProject/iOS/ShareViewController.cs	Uses null-propagation and empty array for CompleteRequest.
tests/dotnet/AppWithXCAssets/AppDelegate.cs	Makes options nullable + CA1422 pragmas.
tests/common/Touch.Unit/Touch.Client/dotnet/shared.csproj	Removes redundant LangVersion/Nullable/WAE settings.
tests/common/TestProjects/MyTVServicesExtension/MyTVServicesExtension.dotnet.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyTVServicesExtension/MyTVServicesExtension.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyTVApp/MyTVApp.dotnet.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyTVApp/MyTVApp.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyTodayExtension/MyTodayExtension.dotnet.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyTodayExtension/MyTodayExtension.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyShareExtension/MyShareExtension.dotnet.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyShareExtension/MyShareExtension.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyPhotoEditingExtension/MyPhotoEditingExtension.dotnet.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyPhotoEditingExtension/MyPhotoEditingExtension.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyKeyboardExtension/MyKeyboardExtension.dotnet.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyKeyboardExtension/MyKeyboardExtension.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyIBToolLinkTest/MyIBToolLinkTest.dotnet.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyIBToolLinkTest/MyIBToolLinkTest.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyDocumentPickerExtension/MyDocumentPickerExtension.dotnet.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyDocumentPickerExtension/MyDocumentPickerExtension.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyActionExtension/MyActionExtension.dotnet.csproj	Removes redundant LangVersion.
tests/common/TestProjects/MyActionExtension/MyActionExtension.csproj	Removes redundant LangVersion.
tests/common/TestProjects/ComplexAssembly/ComplexAssembly.csproj	Removes redundant LangVersion.
tests/common/shared-dotnet.csproj	Removes redundant LangVersion.
tests/common/PlatformInfo.cs	Enables nullable context and applies nullability annotations/guards.
tests/common/MonoTouch.Dialog/shared.csproj	Removes redundant Nullable/WAE settings.
tests/common/mac/MacMain.fs	Adds null-safe handling for ThreadMonitor state.
tests/common/GlobalUsings.cs	Adds System.Diagnostics.CodeAnalysis global using.
tests/common/ExecutionHelper.cs	Enables nullable context and updates signatures/handling.
tests/common/ConfigurationNUnit.cs	Enables nullable context.
tests/common/Configuration.cs	Enables nullable context and adds nullability annotations/guards.
tests/common/AppDelegate.cs	Enables nullable context and updates properties/signatures.
tests/cecil-tests/cecil-tests.csproj	Removes redundant LangVersion/Nullable/WAE settings.
tests/BundledResources/ResourcesTest.cs	Adds null-forgiving on ResourcePath.
tests/bindings-test/RuntimeTest.cs	Makes asyncResult nullable.
tests/bindings-test/Registrar.cs	Adds null-forgiving and reflection safety tweaks.
tests/bindings-test/ProtocolTest.cs	Broad nullability changes + refactoring of helper structs.
tests/bindings-test/dotnet/shared.csproj	Removes redundant WAE settings.
tests/bgen/bgen-tests.csproj	Removes redundant Nullable/TreatWarningsAsErrors.
src/rgen/Microsoft.Macios.Transformer/Microsoft.Macios.Transformer.csproj	Removes redundant Nullable/TreatWarningsAsErrors.
src/rgen/Microsoft.Macios.Transformer.Generator/Microsoft.Macios.Transformer.Generator.csproj	Removes redundant Nullable/LangVersion/TreatWarningsAsErrors.
src/rgen/Microsoft.Macios.Generator/Microsoft.Macios.Generator.csproj	Removes redundant Nullable/LangVersion/TreatWarningsAsErrors.
src/rgen/Microsoft.Macios.Generator.Sample/Microsoft.Macios.Generator.Sample.csproj	Removes redundant Nullable/TreatWarningsAsErrors.
src/rgen/Microsoft.Macios.Bindings.CodeFixers/Microsoft.Macios.Bindings.CodeFixers.csproj	Removes redundant Nullable/LangVersion.
src/rgen/Microsoft.Macios.Bindings.Analyzer/Microsoft.Macios.Bindings.Analyzer.csproj	Removes redundant Nullable/LangVersion/TreatWarningsAsErrors.
src/rgen/Microsoft.Macios.Bindings.Analyzer.Sample/Microsoft.Macios.Bindings.Analyzer.Sample.csproj	Removes redundant Nullable/TreatWarningsAsErrors.
src/rgen/Microsoft.Macios.Binding.Common/Microsoft.Macios.Binding.Common.csproj	Removes redundant Nullable.
src/dotnet.tmpl.csproj	Removes redundant LangVersion.
src/bgen/bgen.csproj	Removes redundant Nullable/WAE settings.
scripts/generate-frameworks-constants/generate-frameworks-constants.cs	Adds null-forgiving on GetFrameworks result.
scripts/Directory.Build.props	Removes redundant Nullable.
scripts/create-windows-html-report/create-windows-html-report.csproj	Removes redundant Nullable.
runtime/bindings-generator.csproj	Removes redundant Nullable/LangVersion.
msbuild/Xamarin.Shared/Xamarin.Shared.props	Removes binding-specific LangVersion setting.
msbuild/Xamarin.MacDev.Tasks/Xamarin.MacDev.Tasks.csproj	Removes redundant LangVersion/Nullable/TreatWarningsAsErrors.
msbuild/Xamarin.Localization.MSBuild/Xamarin.Localization.MSBuild.csproj	Removes redundant Nullable/LangVersion/WAE settings.
msbuild/Xamarin.iOS.Tasks.Windows/Xamarin.iOS.Tasks.Windows.csproj	Removes redundant Nullable/LangVersion/WAE settings.
msbuild/Messaging/Xamarin.Messaging.Build/Xamarin.Messaging.Build.csproj	Removes redundant Nullable/LangVersion/WAE settings.
dotnet/Templates/Microsoft.iOS.Templates/ios/fsharp/SceneDelegate.fs	Adds null-safe window/view handling in template.
docs/preparing-your-app-for-testflight.md	Removes now-redundant Nullable from sample snippet.

[rolfbjarne]

API diff fails because we end up building the previous commit with nullability enabled, which doesn't work.

[vs-mobiletools-engineering-service2]

✅ [PR Build #a033267] Build passed (Build packages) ✅

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[vs-mobiletools-engineering-service2]

✅ [PR Build #a033267] Build passed (Build macOS tests) ✅

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[vs-mobiletools-engineering-service2]

✅ [PR Build #a033267] Build passed (Detect API changes) ✅

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Hash: a0332679c0cb319f3d5537144ffd7025ea4492e9 [PR build]

[vs-mobiletools-engineering-service2]

🔥 Failed to compare API and create generator diff 🔥

Failed to run apidiff

Pipeline on Agent
Hash: a0332679c0cb319f3d5537144ffd7025ea4492e9 [PR build]

[vs-mobiletools-engineering-service2]

🚀 [CI Build #a033267] Test results 🚀

Test results

✅ All tests passed on VSTS: test results.

🎉 All 175 tests passed 🎉

Tests counts

✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (iOS): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (MacCatalyst): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (macOS): All 1 tests passed. (⚠️ Html Report Publish failed ⚠️) Download
✅ dotnettests (Multiple platforms): All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests (tvOS): All 1 tests passed. Html Report (VSDrops) Download
✅ framework: All 2 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 4 tests passed. Html Report (VSDrops) Download
✅ generator: All 5 tests passed. (⚠️ Html Report Publish failed ⚠️) Download
✅ interdependent-binding-projects: All 4 tests passed. Html Report (VSDrops) Download
✅ introspection: All 6 tests passed. [attempt 2] Html Report (VSDrops) Download
✅ linker: All 44 tests passed. Html Report (VSDrops) Download
✅ monotouch (iOS): All 16 tests passed. [attempt 2] Html Report (VSDrops) Download
✅ monotouch (MacCatalyst): All 18 tests passed. Html Report (VSDrops) Download
✅ monotouch (macOS): All 18 tests passed. Html Report (VSDrops) Download
✅ monotouch (tvOS): All 16 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ sharpie: All 1 tests passed. Html Report (VSDrops) Download
✅ windows: All 3 tests passed. [attempt 2] Html Report (VSDrops) Download
✅ xcframework: All 4 tests passed. Html Report (VSDrops) Download
✅ xtro: All 1 tests passed. Html Report (VSDrops) Download

macOS tests

✅ Tests on macOS Monterey (12): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Ventura (13): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Sonoma (14): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Sequoia (15): All 5 tests passed. Html Report (VSDrops) Download
✅ Tests on macOS Tahoe (26): All 5 tests passed. Html Report (VSDrops) Download

Linux Build Verification

✅ Linux build succeeded

Pipeline on Agent
Hash: a0332679c0cb319f3d5537144ffd7025ea4492e9 [PR build]