Restrict partial evaluation to ProjectInstance - #14340
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The opt-in partial (stop-after-pass) evaluation feature was exposed on both Project and ProjectInstance. Project is mutable and cached by ProjectCollection, so a partial Project is a footgun: it either serves stale partial state from the cache or gets silently upgraded to a full evaluation (discarding the perf win) when handed to something that requires later passes. ProjectInstance is an uncached, read-only snapshot and is trap-proof, so partial evaluation now lives there exclusively. Changes: - Remove all partial-eval honoring from Project: the public EvaluationStage property, the ProjectImpl stage field/guards, the partial->Full upgrade blocks in ReevaluateIfNecessary/CreateProjectInstance, and the evaluationStage ctor parameters. Project factories now throw ArgumentException when a non-Full stage is requested via ProjectOptions (new OM_PartialEvaluationNotSupportedForProject resource + xlf entries). - Drop the now-dead cache upgrade-in-place logic in ProjectCollection.LoadProject. - Switch the -getProperty/-getItem (no-target) CLI path in XMake to ProjectInstance.FromFile, and log MSB4025 for pre-evaluation project load failures (Project logged these before throwing; ProjectInstance does not). - Clean up orphaned Project-based JSON item formatter overloads. - Point the partial-eval benchmark at ProjectInstance. - Update the partial-evaluation spec and unit tests accordingly. ProjectInstance retains full partial-evaluation support (EvaluationStage, member guards, OM_PartialEvaluationMemberUnavailable/CannotBuild). Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 008efa7a-b4fc-4f33-9dc7-d37d3f0e93c3
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Pull request overview
Restricts partial (stop-after-pass) evaluation support to ProjectInstance only, removing/denying partial evaluation paths on mutable, ProjectCollection-cached Project to avoid stale cached partial state and hidden upgrade-to-full work.
Changes:
- MSBuild CLI
-getProperty/-getItemno-target path now evaluates viaProjectInstance.FromFileand updates JSON item formatting accordingly. Projectfactories reject non-FullProjectOptions.EvaluationStageandProjectCollection.LoadProjectdrops now-dead partial-upgrade cache logic.- Updates tests, benchmarks, resources/localization, and the partial-evaluation spec to reflect the
ProjectInstance-only model.
Show a summary per file
| File | Description |
|---|---|
| src/MSBuild/XMake.cs | Switches no-target -getProperty/-getItem evaluation to ProjectInstance and adjusts error surfacing and JSON item formatting calls. |
| src/MSBuild/JsonOutputFormatter.cs | Removes Project-based item JSON formatting overloads; keeps ProjectInstance path. |
| src/MSBuild.Benchmarks/PartialEvaluationBenchmark.cs | Updates benchmark to mirror CLI by loading via ProjectInstance. |
| src/Build/Resources/xlf/Strings.zh-Hant.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.zh-Hans.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.tr.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.ru.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.pt-BR.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.pl.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.ko.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.ja.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.it.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.fr.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.es.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.de.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/xlf/Strings.cs.xlf | Adds localized placeholder entry for OM_PartialEvaluationNotSupportedForProject. |
| src/Build/Resources/Strings.resx | Adds OM_PartialEvaluationNotSupportedForProject resource string. |
| src/Build/Definition/ProjectOptions.cs | Documents that partial stages are honored only for ProjectInstance, and Project factories throw. |
| src/Build/Definition/ProjectCollection.cs | Removes partial-eval upgrade-in-place logic from the loaded-project cache. |
| src/Build/Definition/Project.cs | Removes Project partial-eval plumbing/guards and adds up-front rejection for partial stages in Project factory methods. |
| src/Build.UnitTests/Evaluation/PartialEvaluation_Tests.cs | Reworks tests to validate Project factories reject partial stages and ProjectInstance retains behavior. |
| documentation/specs/proposed/partial-evaluation.md | Updates spec to explicitly scope partial evaluation to ProjectInstance and explains why Project does not support it. |
Copilot's findings
- Files reviewed: 22/22 changed files
- Comments generated: 2
- ThrowIfPartialEvaluationRequested now validates options for null up front, so the public Project.From* factories throw ArgumentNullException (not NullReferenceException) when passed null ProjectOptions. Added a covering test. - The -getProperty/-getItem invalid-project error path now prints ex.Message instead of ex.BaseMessage so the project file path is retained in the MSB4025 output, matching the prior Project-based behavior. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 008efa7a-b4fc-4f33-9dc7-d37d3f0e93c3
baronfel
approved these changes
Jul 13, 2026
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Summary
Partial (stop-after-pass) evaluation was exposed on both
ProjectandProjectInstance. This PR restricts it toProjectInstanceonly.Projectis mutable and cached byProjectCollection, which makes a partially-evaluatedProjecta footgun:Projectcan be handed back to a caller expecting a full evaluation, serving stale partial state, orProjectInstanceis an uncached, read-only evaluation snapshot with none of these traps, so partial evaluation now lives there exclusively.Changes
Project: removed all partial-eval honoring — the publicEvaluationStageproperty, theProjectImplstage field + member guards, the partial→Full upgrade blocks inReevaluateIfNecessary/CreateProjectInstance, and theevaluationStageconstructor parameters.Project.FromFile/FromProjectRootElement/FromXmlReadernow throwArgumentExceptionwhen a non-Fullstage is requested viaProjectOptions(newOM_PartialEvaluationNotSupportedForProjectresource + xlf entries).ProjectCollection.LoadProject: dropped the now-dead partial cache upgrade-in-place logic.XMake(-getProperty/-getItem, no-target path): switched fromProject.FromFiletoProjectInstance.FromFile.ProjectInstancedoes not log pre-evaluation project-load failures (malformed XML) the wayProjectdid, so the catch block now surfacesMSB4025in canonical format (guarded byHasBeenLoggedto avoid double-logging genuine evaluation errors).JsonOutputFormatter: removed orphanedProject-based item formatter overloads.PartialEvaluationBenchmarknow usesProjectInstance.ProjectInstanceretains full partial-evaluation support (EvaluationStage, member guards,OM_PartialEvaluationMemberUnavailable/OM_PartialEvaluationCannotBuild).Testing
PartialEvaluation_Tests(Engine.UnitTests): 13/13 pass.-getProperty/-getItemCLI tests + fullXMakeAppTests(CommandLine.UnitTests): pass (incl.GetPropertyWithInvalidProjectThrowsInvalidProjectFileExceptionNotInternalError, which verifiesMSB4025is still emitted).