Use partial evaluation for -preprocess, schema validation, and .wdproj dependency scan

[ViktorHofer]

Context

Builds on the opt-in partial (stop-after-pass) evaluation added in #14290 and adopted by -getProperty/-getItem in #14296. This extends partial evaluation to three more consumers that only read early-pass data and never build a project.

Changes

Consumer	Data read	Stops after
-preprocess / -pp (SaveLogicalProject)	import closure only (resolved in pass 1)	Properties
-validate schema validation	project ToolsVersion only	Properties (net472 only)
SolutionProjectGenerator.ScanProjectDependencies (legacy .wdproj)	ProjectDependency items + SourceWebProject property	Items

All three skip the later using-tasks and target-registration passes.

Change wave

Gated behind change wave 18.10 (same wave as #14296). Setting MSBUILDDISABLEFEATURESFROMVERSION=18.10 restores the historical full-evaluation behavior.

Tests

• New PreprocessUsesPartialEvaluation change-wave test in XMake_Tests.cs, mirroring the existing -getProperty test: a project whose only error is in the targets pass preprocesses successfully with the wave on, and fails (full evaluation) when the wave is disabled. Passes on net10.0 + net472.
• Regression green: engine dependency tests (48).
• Clean build of Microsoft.Build and the MSBuild CLI (net10.0 + net472), 0 warnings / 0 errors.

Docs

• Documents the new consumers in ChangeWaves.md (and fixes a stray typo on the existing 18.10 entry).

[Copilot]

Pull request overview

Extends the opt-in partial (stop-after-pass) evaluation feature (ChangeWave 18.10) to additional MSBuild consumers that only need early-pass data, reducing unnecessary evaluation work while preserving an opt-out path via MSBUILDDISABLEFEATURESFROMVERSION.

Changes:

• Switch -validate (schema validation) and -preprocess to stop evaluation after the Properties pass when ChangeWave 18.10 is enabled.
• Update .wdproj dependency scanning in SolutionProjectGenerator.ScanProjectDependencies to stop after the Items pass when ChangeWave 18.10 is enabled.
• Add a new change-wave test covering -preprocess and update ChangeWaves documentation.

Show a summary per file

File	Description
src/MSBuild/XMake.cs	Uses ProjectOptions.EvaluationStage to avoid full evaluation for schema validation and preprocess under wave 18.10.
src/MSBuild.UnitTests/XMake_Tests.cs	Adds a change-wave regression test verifying -preprocess benefits from partial evaluation.
src/Build/Construction/Solution/SolutionProjectGenerator.cs	Uses partial evaluation (stop-after Items) for .wdproj dependency scanning under wave 18.10.
documentation/wiki/ChangeWaves.md	Documents additional 18.10 consumers and fixes an existing formatting/typo issue.

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 4

[ViktorHofer]

/review

[github-actions]

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Expert reviewer subagent posted review on PR #14326. Main finding: missing change-wave tests for -validate and ScanProjectDependencies consumers. Implementation itself is correct. Subagent handled all safe-output writes.

[github-actions]

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Review Summary — PR #14326 (Partial evaluation for -preprocess, schema validation, .wdproj)

Positive observations

• ChangeWave 18.10 gates all three changes correctly; opt-out via MSBUILDDISABLEFEATURESFROMVERSION=18.10 is preserved.
• ChangeWaves.md is updated and the pre-existing typo (14290)arget) → 14296) is fixed.
• EvaluationStage choices are correct: Properties is sufficient for preprocessing (import closure is resolved in pass 1) and for schema validation (only ToolsVersion is needed); Items is correct for the .wdproj scan (ProjectDependency items + SourceWebProject property).
• Project.FromFile + ProjectOptions is the right API; it avoids adding the project to the collection under the old LoadProject path, and UnloadProject is called where it was before.
• The PreprocessUsesPartialEvaluation test is well-structured and tests both wave-enabled and wave-disabled paths, matching the pattern set by GetPropertyWithoutTargetUsesPartialEvaluation.

Blocking / Major issue

Missing test coverage for schema validation and .wdproj dependency scan (see inline comment on XMake_Tests.cs line 933).

The PR introduces partial-evaluation changes to three consumers but adds a test for only one of them. The other two — schema validation (-validate, .NET Framework only) and ScanProjectDependencies (.wdproj) — have no test verifying:

• that partial evaluation is used when wave 18.10 is enabled, and
• that full evaluation is restored when the wave is disabled.

The .wdproj path is especially important to cover because it is the only consumer that stops at Items (not Properties) and it lives in a different assembly (SolutionProjectGenerator), so it needs its own integration test.

Minor observations

• ScanProjectDependencies creates Project.FromFile inside a try/catch but never calls UnloadProject before or after the exception path. The old new Project(...) call had the same behaviour, so this is unchanged, but it could be noted as a follow-up.
• The PR description says schema validation partial evaluation is "net472 only" — this is correct because the entire block is inside #if FEATURE_XML_SCHEMA_VALIDATION, but the code comment inside the block does not mention this conditional compilation guard. A brief note would help future readers.

Generated by Expert Code Review (command) for #14326 · 245.1 AIC · ⊞ 30.1K
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[ViktorHofer]

These code paths aren't worth touching and they all use Project and not ProjectInstance.