Remove redundant #nullable disable from 153 files by Copilot · Pull Request #13157 · dotnet/msbuild

Copilot · 2026-01-30T15:49:25Z

Context

Projects have <Nullable>enable</Nullable> at the project level, but many files retain legacy #nullable disable directives. Files that are already nullable-clean don't need the directive.

Changes Made

Removed #nullable disable from files verified to build without nullable warnings:

Project	Cleaned	Remaining
Utilities	5	21
Build	79	284
MSBuild	2	11
Tasks	41	86
Shared	26	75
Total	153	477

Shared folder required full repo builds since files compile into multiple projects.

Files retained the directive when:

Nullable warnings present in any TFM (net472, net10.0)
Interface files (changing nullability affects implementors)
Exception classes (signatures affect other code)
Public API methods called from non-nullable contexts

Testing

Each project built individually with 0 warnings
Full repo build: 0 warnings, 0 errors
Fixed double blank lines left by directive removal

Notes

None

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

These files are already nullable-clean and don't need the directive: - src/Utilities/ApiContract.cs - src/Utilities/AssemblyFolders/AssemblyFoldersExInfo.cs - src/Utilities/AssemblyFolders/AssemblyFoldersFromConfigInfo.cs - src/Utilities/SDKType.cs - src/Utilities/TrackedDependencies/CanonicalTrackedFilesHelper.cs Co-authored-by: rainersigwald <3347530+rainersigwald@users.noreply.github.com>

These files are already nullable-clean and don't need the directive.

rainersigwald · 2026-01-30T20:22:02Z

@copilot I pushed a change that does the same for Framework--now do the Build assembly/folder.

These files are already nullable-clean and don't need the directive. Files are spread across various subsystems including: - BackEnd/Components (logging, caching, SDK resolution, scheduler) - Collections (HashHelpers, CopyOnReadEnumerable) - Construction/Solution - Definition (metadata, settings, toolsets) - Evaluation/Conditionals (expression nodes) - FileSystem, Globbing, Graph, Instance - Logging (BinaryLogger enums, ConsoleConfiguration) - ObjectModelRemoting (all link classes) Co-authored-by: rainersigwald <3347530+rainersigwald@users.noreply.github.com>

Copilot · 2026-01-30T20:37:50Z

@copilot I pushed a change that does the same for Framework--now do the Build assembly/folder.

Done in 77db019. Removed #nullable disable from 79 files in the Build assembly that are nullable-clean. The remaining 284 files have nullable warnings and must keep the directive for now.

rainersigwald · 2026-01-30T21:21:59Z

@copilot do MSBuild and then Tasks.

MSBuild project (3 files): - DistributedLoggerRecord.cs - NodeEndpointOutOfProcTaskHost.cs - ProjectSchemaValidationHandler.cs Tasks project (41 files): - AppConfig: AppConfigException.cs, RuntimeSection.cs - AssemblyDependency: 13 files (enums, exceptions, helpers) - BootstrapperUtil: 6 files - DataDriven: DataDrivenToolTask.cs - FileIO: HashEncoding.cs - ManifestUtil: 10 files (constants, formatters, utilities) - ResourceHandling: 6 files - RoslynCodeTaskFactory: RoslynCodeTaskFactoryCodeType.cs Co-authored-by: rainersigwald <3347530+rainersigwald@users.noreply.github.com>

Copilot · 2026-01-30T21:36:43Z

@copilot do MSBuild and then Tasks.

Done in e5dc39c.

MSBuild: Removed #nullable disable from 3 files (DistributedLoggerRecord, NodeEndpointOutOfProcTaskHost, ProjectSchemaValidationHandler). 10 of 13 files still need the directive.

Tasks: Removed #nullable disable from 41 files across AppConfig, AssemblyDependency, BootstrapperUtil, DataDriven, FileIO, ManifestUtil, ResourceHandling, and RoslynCodeTaskFactory. 86 of 127 files still need the directive.

Files cleaned: - AssemblyFolders: AssemblyFoldersFromConfig.cs - FileSystem: 6 files (CachingFileSystemWrapper, FileSystems, ManagedFileSystem, etc.) - LanguageParser: 4 files (tokenChar, tokenCharReader, CSharptokenCharReader, VisualBasictokenCharReader) - Other: BufferedReadStream, Constants, ExtensionFoldersRegistryKey, FileDelegates, FileUtilitiesRegex, MetadataConversionUtilities, NodeBuildComplete, NodeEngineShutdownReason, ProcessExtensions, QuotingUtilities, TaskHostTaskCancelled, VisualStudioConstants, XMakeElements, XamlUtilities 75 of 101 files still need the directive (compiled into multiple projects with different nullable contexts). Co-authored-by: rainersigwald <3347530+rainersigwald@users.noreply.github.com>

rainersigwald · 2026-01-30T22:27:32Z

@copilot looks like the build is failing with

src\MSBuild\ProjectSchemaValidationHandler.cs(226,92): error CS8600: (NETCORE_ENGINEERING_TELEMETRY=Build) Converting null literal or possible null value to non-nullable type.

This file has nullable warnings and cannot have the directive removed. Co-authored-by: rainersigwald <3347530+rainersigwald@users.noreply.github.com>

Copilot · 2026-01-30T22:31:36Z

@copilot looks like the build is failing with

...

Fixed in 0daa673. Restored #nullable disable to ProjectSchemaValidationHandler.cs - this file has a nullable warning at line 226 where FormatResourceStringStripCodeAndKeyword returns a nullable string.

Copilot

Pull request overview

This PR removes redundant #nullable disable directives from 153 files across the MSBuild codebase. These files are already nullable-clean and don't require the directive since their projects have <Nullable>enable</Nullable> at the project level.

Changes:

Removed #nullable disable from 153 files (Utilities: 5, Build: 79, MSBuild: 2, Tasks: 41, Shared: 26)
Fixed double blank lines left by directive removal to maintain consistent formatting

Reviewed changes

Copilot reviewed 174 out of 174 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/Utilities/*.cs (5 files)	Removed nullable disable from TrackedDependencies, AssemblyFolders, and SDKType files
src/Tasks/*/.cs (41 files)	Removed nullable disable from ResourceHandling, ManifestUtil, BootstrapperUtil, AssemblyDependency, AppConfig, DataDriven, and FileIO files
src/Shared/*/.cs (26 files)	Removed nullable disable from FileSystem, LanguageParser, and utility files
src/MSBuild/*.cs (2 files)	Removed nullable disable from NodeEndpointOutOfProcTaskHost and DistributedLoggerRecord
src/Framework/*/.cs (26 files)	Removed nullable disable from XamlTypes, Sdk, Profiler, and attribute files
src/Build/*/.cs (53 files)	Removed nullable disable from ObjectModelRemoting, Logging, Instance, Graph, Globbing, FileSystem, Evaluation, Definition, Construction, Collections, and BackEnd files

### Context Projects have `<Nullable>enable</Nullable>` at the project level, but many files retain legacy `#nullable disable` directives. Files that are already nullable-clean don't need the directive. ### Changes Made Removed `#nullable disable` from files verified to build without nullable warnings: | Project | Cleaned | Remaining | |---------|---------|-----------| | Utilities | 5 | 21 | | Build | 79 | 284 | | MSBuild | 2 | 11 | | Tasks | 41 | 86 | | Shared | 26 | 75 | | **Total** | **153** | **477** | **Shared folder** required full repo builds since files compile into multiple projects. Files retained the directive when: - Nullable warnings present in any TFM (net472, net10.0) - Interface files (changing nullability affects implementors) - Exception classes (signatures affect other code) - Public API methods called from non-nullable contexts ### Testing - Each project built individually with 0 warnings - Full repo build: 0 warnings, 0 errors - Fixed double blank lines left by directive removal ### Notes None  --- 💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more [Copilot coding agent tips](https://gh.io/copilot-coding-agent-tips) in the docs. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: rainersigwald <3347530+rainersigwald@users.noreply.github.com> Co-authored-by: Rainer Sigwald <raines@microsoft.com>

The doc comment explicitly mentions returning null and the SDK can do so, which caused a break in dotnet/dotnet#4579: src\sdk\src\Resolvers\Microsoft.NET.Sdk.WorkloadMSBuildSdkResolver\WorkloadSdkResolver.cs(35,36): error CS8764: Nullability of return type doesn't match overridden member (possibly because of nullability attributes). Follow up to #13157 / 0172c58.

### Context Projects have `<Nullable>enable</Nullable>` at the project level, but many files retain legacy `#nullable disable` directives. Files that are already nullable-clean don't need the directive. ### Changes Made Removed `#nullable disable` from files verified to build without nullable warnings: | Project | Cleaned | Remaining | |---------|---------|-----------| | Utilities | 5 | 21 | | Build | 79 | 284 | | MSBuild | 2 | 11 | | Tasks | 41 | 86 | | Shared | 26 | 75 | | **Total** | **153** | **477** | **Shared folder** required full repo builds since files compile into multiple projects. Files retained the directive when: - Nullable warnings present in any TFM (net472, net10.0) - Interface files (changing nullability affects implementors) - Exception classes (signatures affect other code) - Public API methods called from non-nullable contexts ### Testing - Each project built individually with 0 warnings - Full repo build: 0 warnings, 0 errors - Fixed double blank lines left by directive removal ### Notes None  --- 💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more [Copilot coding agent tips](https://gh.io/copilot-coding-agent-tips) in the docs. --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: rainersigwald <3347530+rainersigwald@users.noreply.github.com> Co-authored-by: Rainer Sigwald <raines@microsoft.com>

The doc comment explicitly mentions returning null and the SDK can do so, which caused a break in dotnet/dotnet#4579: src\sdk\src\Resolvers\Microsoft.NET.Sdk.WorkloadMSBuildSdkResolver\WorkloadSdkResolver.cs(35,36): error CS8764: Nullability of return type doesn't match overridden member (possibly because of nullability attributes). Follow up to dotnet#13157 / 0172c58.

Initial plan

6fa52be

Copilot AI assigned Copilot and rainersigwald Jan 30, 2026

Copilot started work on behalf of rainersigwald January 30, 2026 15:49 View session

Copilot AI changed the title ~~[WIP] Remove redundant #nullable disable directives from codebase~~ Remove redundant #nullable disable from 5 Utilities files Jan 30, 2026

Copilot AI requested a review from rainersigwald January 30, 2026 16:01

Copilot finished work on behalf of rainersigwald January 30, 2026 16:01

Remove redundant #nullable disable from 21 Framework files

3db473b

These files are already nullable-clean and don't need the directive.

Copilot started work on behalf of rainersigwald January 30, 2026 20:22 View session

Copilot AI changed the title ~~Remove redundant #nullable disable from 5 Utilities files~~ Remove redundant #nullable disable from Utilities and Build files Jan 30, 2026

Copilot finished work on behalf of rainersigwald January 30, 2026 21:21

Copilot started work on behalf of rainersigwald January 30, 2026 21:22 View session

Copilot AI changed the title ~~Remove redundant #nullable disable from Utilities and Build files~~ Remove redundant #nullable disable from Utilities, Build, MSBuild, and Tasks files Jan 30, 2026

Copilot finished work on behalf of rainersigwald January 30, 2026 21:37

Copilot started work on behalf of rainersigwald January 30, 2026 21:44 View session

Copilot AI changed the title ~~Remove redundant #nullable disable from Utilities, Build, MSBuild, and Tasks files~~ Remove redundant #nullable disable from 154 files Jan 30, 2026

Copilot finished work on behalf of rainersigwald January 30, 2026 22:01

Copilot started work on behalf of rainersigwald January 30, 2026 22:27 View session

Restore #nullable disable to ProjectSchemaValidationHandler.cs

0daa673

This file has nullable warnings and cannot have the directive removed. Co-authored-by: rainersigwald <3347530+rainersigwald@users.noreply.github.com>

Copilot AI changed the title ~~Remove redundant #nullable disable from 154 files~~ Remove redundant #nullable disable from 153 files Jan 30, 2026

Copilot finished work on behalf of rainersigwald January 30, 2026 22:32

Fix unnecessary BOM change

68127e8

rainersigwald approved these changes Feb 2, 2026

View reviewed changes

rainersigwald marked this pull request as ready for review February 2, 2026 15:14

Copilot AI review requested due to automatic review settings February 2, 2026 15:14

Copilot started reviewing on behalf of rainersigwald February 2, 2026 15:14 View session

Copilot AI reviewed Feb 2, 2026

View reviewed changes

YuliiaKovalova approved these changes Feb 3, 2026

View reviewed changes

YuliiaKovalova merged commit 0172c58 into main Feb 3, 2026
15 checks passed

YuliiaKovalova deleted the copilot/remove-redundant-nullable-directives branch February 3, 2026 09:39

dotnet-maestro bot mentioned this pull request Feb 4, 2026

[main] Source code updates from dotnet/msbuild dotnet/dotnet#4579

Merged

rainersigwald mentioned this pull request Feb 4, 2026

Allow null SdkResult from SdkResolver.Resolve #13197

Merged

dotnet-maestro bot mentioned this pull request Mar 3, 2026

[release/10.0.3xx] Source code updates from dotnet/msbuild dotnet/dotnet#5204

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Remove redundant #nullable disable from 153 files#13157

Remove redundant #nullable disable from 153 files#13157
YuliiaKovalova merged 8 commits intomainfrom
copilot/remove-redundant-nullable-directives

Copilot AI commented Jan 30, 2026 •

edited

Loading

Uh oh!

rainersigwald commented Jan 30, 2026

Uh oh!

Copilot AI commented Jan 30, 2026

Uh oh!

rainersigwald commented Jan 30, 2026

Uh oh!

Copilot AI commented Jan 30, 2026

Uh oh!

rainersigwald commented Jan 30, 2026

Uh oh!

Copilot AI commented Jan 30, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Conversation

Copilot AI commented Jan 30, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Context

Changes Made

Testing

Notes

Uh oh!

rainersigwald commented Jan 30, 2026

Uh oh!

Copilot AI commented Jan 30, 2026

Uh oh!

rainersigwald commented Jan 30, 2026

Uh oh!

Copilot AI commented Jan 30, 2026

Uh oh!

rainersigwald commented Jan 30, 2026

Uh oh!

Copilot AI commented Jan 30, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Copilot AI commented Jan 30, 2026 •

edited

Loading