Fix chained item function empty result comparison in conditions#12901
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JanProvaznik merged 4 commits intoFeb 2, 2026
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The issue is that when chaining item functions like:
@(TestItem->WithMetadataValue('Identity', 'Test1')->WithMetadataValue('Foo', 'Baz'))
The result incorrectly evaluates as non-empty when compared in a condition, even though the actual result is empty.
Initial hypothesis was that the BreakOnNotEmpty optimization in Transform() was breaking early after the first transform. However, testing revealed that the Transform() method is NOT being called at all for chained transforms with BreakOnNotEmpty option.
This suggests the bug is elsewhere - possibly in how ExpressionShredder parses chained transforms or in how they're evaluated separately.
Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>
When chaining item functions like @(Item->Func1()->Func2()), and the final result is empty, the condition comparison with empty string was incorrectly evaluating to false. The bug was in the Transform method in Expander.cs. The original code checked for BreakOnNotEmpty after EACH intermediate transform, causing it to break early when an intermediate result was non-empty, even if subsequent transforms would filter to an empty result. The fix moves the BreakOnNotEmpty check to after ALL transforms in the chain complete, ensuring we only check the final result, not intermediate ones. Added a unit test to verify the fix works correctly. Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>
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Pull request overview
This PR fixes a bug (#12877) where chained item functions incorrectly evaluated as non-empty in conditions when the final result was actually empty. The issue occurred because the BreakOnNotEmpty optimization was checking intermediate results after each transform in the chain, rather than checking only the final result after all transforms completed.
Key changes:
- Modified the
Transformmethod inExpander.csto delay theBreakOnNotEmptycheck until after all chained transforms complete - Added a test case to verify chained item functions with empty results are correctly evaluated in conditions
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.
| File | Description |
|---|---|
| src/Build/Evaluation/Expander.cs | Moved BreakOnNotEmpty optimization check from inside the transform loop to after all transforms complete, ensuring correct evaluation of chained item functions |
| src/Build.UnitTests/Evaluation/Expander_Tests.cs | Added test case ChainedItemFunctionEmptyResultInCondition to verify the bug fix with a scenario using chained WithMetadataValue functions |
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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: JanProvaznik <25267098+JanProvaznik@users.noreply.github.com>
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Updated [Microsoft.Build](https://github.com/dotnet/msbuild) from 18.4.0 to 18.6.3. <details> <summary>Release notes</summary> _Sourced from [Microsoft.Build's releases](https://github.com/dotnet/msbuild/releases)._ ## 18.6.3 ## What's Changed * Improve cross-platform node discovery for reuse with NodeMode filtering by @Copilot in dotnet/msbuild#13256 * Updated common types XSD to remove errors from redefining `Include` attributes by @glektarssza in dotnet/msbuild#13284 * Update VersionPrefix to 18.6.0 + insertion flow by @MichalPavlik in dotnet/msbuild#13296 * Log warnings for skipped STR resource keys instead of failing the build by @OvesN in dotnet/msbuild#13291 * Isolate MSBuildTaskHost from the rest of MSBuild Codebase by @DustinCampbell in dotnet/msbuild#13232 * Improve error messages when ToolTask overrides exit code 0 to -1 due to logged errors by @OvesN in dotnet/msbuild#13303 * Migrate Exec task to TaskEnvironment API by @Copilot in dotnet/msbuild#13171 * Enhance crash telemetry with richer diagnostics and EndBuild hang detection by @YuliiaKovalova in dotnet/msbuild#13304 * [main] Update dependencies from nuget/nuget.client by @dotnet-maestro[bot] in dotnet/msbuild#13309 * [IBuildEngine callbacks] Stage 2: RequestCores/ReleaseCores by @JanProvaznik in dotnet/msbuild#13306 * Only get command line args names on modern .NET by @baronfel in dotnet/msbuild#13314 * Detect and correct worker node over-provisioning by @Copilot in dotnet/msbuild#13220 * Add App Host Support for MSBuild by @YuliiaKovalova in dotnet/msbuild#13175 * [main] Update dependencies from dotnet/arcade by @dotnet-maestro[bot] in dotnet/msbuild#13311 * Fix ObjectDisposedException in BuildsWhileBuildIsRunningOnServer test by @Copilot in dotnet/msbuild#13316 * Add PoC of pipelines check skill by @JanKrivanek in dotnet/msbuild#13242 * Fix CodeSign.MissingSigningCert for xsd/Update-MSBuildXsds.ps1 by @JanProvaznik in dotnet/msbuild#13320 * Fix task host launch regressions from 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code updates from dotnet/dotnet by @dotnet-maestro[bot] in dotnet/msbuild#13353 * Fix ScheduleTimeRecord.AccumulatedTime hang during solution close by @YuliiaKovalova in dotnet/msbuild#13375 * Update runtime package references to 10.0.3 by @Copilot in dotnet/msbuild#13376 * [main] Source code updates from dotnet/dotnet by @dotnet-maestro[bot] in dotnet/msbuild#13378 * Fix ProjectImports.zip regression from shared FileUtilities statics by @JanProvaznik in dotnet/msbuild#13382 * Enrich EndBuild hang diagnostics with logging service and submission state by @YuliiaKovalova in dotnet/msbuild#13385 * Enhance path normalization: add handling for consecutive directory separators by @tommcdon in dotnet/msbuild#13369 * Move task environment drivers to Framework. by @AR-May in dotnet/msbuild#13380 * Update MicrosoftBuildVersion in analyzer template by @github-actions[bot] in dotnet/msbuild#13298 * Replace ProjectCacheService null Project crash with diagnostic telemetry by @YuliiaKovalova in dotnet/msbuild#13396 * Add agentic workflow to auto-close PRs older than 180 days by @Copilot in dotnet/msbuild#13400 * Localized file check-in by OneLocBuild Task: Build definition ID 9434: Build ID 13575337 by @dotnet-bot in dotnet/msbuild#13394 * Respect MSBUILDPRESERVETOOLTEMPFILES in ProcessExit cleanup by @DmitriyShepelev in dotnet/msbuild#13395 ... (truncated) ## 18.5.4 ## What's Changed * remove dead code by @SimaTian in dotnet/msbuild#13125 * Update VersionPrefix to 18.5.0 + insertion flow by @YuliiaKovalova in dotnet/msbuild#13134 * add multithreaded task migration agent skill by @JanProvaznik in dotnet/msbuild#13131 * Update MicrosoftBuildVersion in analyzer template by @github-actions[bot] in dotnet/msbuild#13139 * Migrate VerifyFileHash task to TaskEnvironment API by @Copilot in dotnet/msbuild#13112 * Migrate GetFileHash tasks to TaskEnvironment API by @Copilot in dotnet/msbuild#13111 * Diagram of VS/SDK component interactions by @rainersigwald in dotnet/msbuild#13127 * Fix package validation telemetry assembly resolution warnings by @JanProvaznik in dotnet/msbuild#13144 * Adds validation to throw MSB4259 when property references contain leading or trailing whitespace outside of conditions. by @huulinhnguyen-dev in dotnet/msbuild#13076 * Localized file check-in by OneLocBuild Task: Build definition ID 9434: Build ID 13203963 by @dotnet-bot in dotnet/msbuild#13151 * Add MSBuild app host design by @YuliiaKovalova in dotnet/msbuild#12857 * Add Stabilize-Release.ps1 script for release process by @rainersigwald in dotnet/msbuild#13146 * Fix chained item function empty result comparison in conditions by @JanProvaznik in dotnet/msbuild#12901 * [main] Update dependencies from dotnet/roslyn by @dotnet-maestro[bot] in dotnet/msbuild#13162 * [main] Update dependencies from dotnet/arcade by @dotnet-maestro[bot] in dotnet/msbuild#13160 * Localized file check-in by OneLocBuild Task: Build definition ID 9434: Build ID 13217622 by @dotnet-bot in dotnet/msbuild#13163 * Fix items logged as type name during -getitem argument by @Copilot in dotnet/msbuild#13166 * Respect NetCoreSdkRoot property for TaskHostParameters by @ViktorHofer in dotnet/msbuild#13176 * Remove MachineIndependent configuration by @Copilot in dotnet/msbuild#13180 * Remove redundant #nullable disable from 153 files by @Copilot in dotnet/msbuild#13157 * Revert #13076 "Adds validation to throw MSB4259 when property references contain leading or trailing whitespace outside of conditions. by @JanProvaznik in dotnet/msbuild#13184 * Convert MSBuild.sln to slnx format and upate refs by @ViktorHofer in dotnet/msbuild#13185 * Implement IMultiThreadableTask for Move task by @Copilot in dotnet/msbuild#13108 * Add hostservices translation support for clr 4 task host by @YuliiaKovalova in dotnet/msbuild#13154 * Handle null ProjectFile in InvalidProjectFileException by @ViktorHofer in dotnet/msbuild#13179 * Add $(LatestDotNetCoreForMSBuild) infrastructure for centralized framework targeting by @Copilot in dotnet/msbuild#13189 * Fix TaskHost crash when task returns string[] with null elements by @JanProvaznik in dotnet/msbuild#13190 * Revert "Refactor Microsoft.IO usage" by @YuliiaKovalova in dotnet/msbuild#13194 * Allow null SdkResult from SdkResolver.Resolve by @rainersigwald in dotnet/msbuild#13197 * Skill to test changes using just-built MSBuild by @rainersigwald in dotnet/msbuild#13202 * Tell Copilot not to allow breaking changes by @rainersigwald in dotnet/msbuild#13200 * Make nologo switch accept boolean values to enable explicit logo display control by @Copilot in dotnet/msbuild#12541 * Migrate Unzip task to use TaskEnvironment API by @Copilot in dotnet/msbuild#13109 * Migrate ZipDirectory task to TaskEnvironment API by @Copilot in dotnet/msbuild#13110 * Localized file check-in by OneLocBuild Task: Build definition ID 9434: Build ID 13246767 by @dotnet-bot in dotnet/msbuild#13204 * Add .NET Standard compatibility warnings by @ViktorHofer in dotnet/msbuild#13187 * Make WriteCodeFragment task locale-independent for reproducible builds by @Copilot in dotnet/msbuild#13192 * Localized file check-in by OneLocBuild Task: Build definition ID 9434: Build ID 13249478 by @dotnet-bot in dotnet/msbuild#13207 * Fix TerminalLogger IndexOutOfRangeException when replaying binlog with fewer nodes by @Copilot in dotnet/msbuild#12809 * Migrate DownloadFile task to use TaskEnvironment API by @Copilot in dotnet/msbuild#13113 * Add CI job for 2-stage build with -mt mode by @Copilot in dotnet/msbuild#13124 * Localize AbsolutePath validation messages by @JanProvaznik in dotnet/msbuild#13115 * Refactor FrameworkFileUtilities for better performance by @AR-May in dotnet/msbuild#13143 * Add agent instructions for MSBuild repository by @YuliiaKovalova in dotnet/msbuild#13198 * Add GetCanonicalForm to the AbsolutePath API by @AR-May in dotnet/msbuild#13088 * Shouldly 4.3.0 by @rainersigwald in dotnet/msbuild#13213 * Migrate WriteCodeFragment task to use TaskEnvironment API by @Copilot in dotnet/msbuild#13169 * Run the issue-labeler over pull requests using polling by @Copilot in dotnet/msbuild#13223 * [main] Update dependencies from dotnet/arcade by @dotnet-maestro[bot] in dotnet/msbuild#13225 ... 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Fixes #12877
Context
Chained item functions incorrectly evaluate as non-empty in conditions when the final result is empty. For example:
The first transform matches
Test1, but the second filters it out (Foo="Bar"!="Baz"). The final result is empty, yet the condition fails.Changes Made
src/Build/Evaluation/Expander.cs
BreakOnNotEmptycheck inTransformmethod to execute after all chained transforms complete, not after each intermediate transformsrc/Build.UnitTests/Evaluation/Expander_Tests.cs
ChainedItemFunctionEmptyResultInConditiontest verifying the fixTesting
Notes
BreakOnNotEmptyoptimization (condition evaluation path), not in normal property expansion.