[XAML] XIHR: remove the now-dead __version field and StableContentHash by StephaneDelcroix · Pull Request #36912 · dotnet/maui

StephaneDelcroix · 2026-07-29T15:36:25Z

Note

Are you waiting for the changes in this PR to be merged?
It would be very helpful if you could test the resulting artifacts from this PR and let us know in a comment if this change resolves your issue. Thank you!

Description

Follow-up to #36833 addressing @tmat's review comment on GeneratorHelpers.StableContentHash (that xxHash128 would be a better hash for the __version content identity).

Once #36833 moved diagnostics to classify a delta by the empty-vs-non-empty UpdateComponent() body (rather than a stamped identity), nothing reads the generated __version field anymore — it is write-only. So instead of swapping the hash algorithm, this removes the field and its hash entirely:

InitializeComponent no longer emits private int __version nor stamps it; drops the __version = 0 reset on the legacy ResourceProvider2 fallback path.
Removes GeneratorHelpers.StableContentHash (its only consumer was the __version stamp).
Updates the obsolete __version-era doc comments across the SourceGen writers.
Tests: drops the three __version-field assertions and the __version parts of the determinism test, repurposing them to the surviving registration / reverse-transition behavior.

No behavior change — __version was unused.

Scope note

@tmat's second comment (the mutable static XamlHotReloadState cache being brittle when Roslyn runs source generators on multiple/throwaway compilations) is a separate, larger architectural question and is not addressed here — it's tracked for a dedicated follow-up. This PR is limited to removing the dead field/hash.

Testing

SourceGen.UnitTests: 460 green.

Note on base

Stacked on #36833 (the __version field is only dead after that PR's empty-UC diagnostics). Targets feature/xihr-deterministic-versioning; GitHub will retarget to net11.0 once #36833 merges.

azure-pipelines · 2026-07-29T15:36:36Z

Azure Pipelines: 1 pipeline(s) were filtered out due to trigger conditions. There may be pipelines that require an authorized user to comment /azp run to run.

github-actions · 2026-07-29T17:32:49Z

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.sh | bash -s -- 36912

Or

Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/maui/main/eng/scripts/get-maui-pr.ps1) } 36912"

Copilot

Pull request overview

This PR removes the generated XIHR __version field and the now-unused GeneratorHelpers.StableContentHash helper, and updates XIHR source-gen tests/docs accordingly. The goal is to simplify the incremental hot reload generator by eliminating write-only identity stamping that is no longer read after the diagnostics/classification changes introduced in #36833.

Changes:

Stop emitting/stamping __version in generated InitializeComponent() output and remove the StableContentHash helper.
Update XIHR generator/writer comments to reflect the current “empty vs non-empty UpdateComponent body” behavior.
Update SourceGen unit tests to drop __version assertions and refocus on registration/tracking + reverse-transition behavior.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Controls/tests/SourceGen.UnitTests/XamlIncrementalHotReloadE2ETests.cs	Removes `__version`-identity assertions; refocuses the revert test on reverse-transition UC behavior.
src/Controls/tests/SourceGen.UnitTests/XamlIncrementalHotReloadCSharpExpressionTests.cs	Updates the test to validate registration emission rather than `__version` field emission.
src/Controls/tests/SourceGen.UnitTests/InitializeComponent/IncrementalHotReloadICTests.cs	Removes `__version`-specific tests/assertions and keeps coverage focused on IHR artifacts.
src/Controls/src/SourceGen/XamlHotReloadState.cs	Updates comments to remove `__version`-related wording while keeping internal version bookkeeping.
src/Controls/src/SourceGen/XamlGenerator.cs	Updates comments around IHR state seeding/diff timing to reflect current behavior.
src/Controls/src/SourceGen/UpdateComponentCodeWriter.cs	Updates remarks/docs for the new UC shape; (also contains a doc-comment formatting issue noted in review).
src/Controls/src/SourceGen/ProjectItem.cs	Updates `EnableIncrementalHotReload` docs to describe Track/Register behavior (no `__version`).
src/Controls/src/SourceGen/InitializeComponentCodeWriter.cs	Removes `__version` field emission and stamping; keeps registry + Track emission.
src/Controls/src/SourceGen/GeneratorHelpers.cs	Removes `StableContentHash` implementation and related documentation.

 	/// <summary>
-	/// Assembles a complete <c>UpdateComponent()</c> source file from accumulated patch bodies.
-	/// Each patch body becomes an <c>if (__version == N) { ... }</c> block inside the single method.
-	/// </summary>
 	/// <summary>


 		Assert.DoesNotContain("__version", text, StringComparison.Ordinal);
 		Assert.DoesNotContain("XamlComponentRegistry.Register", text, StringComparison.Ordinal);
 	}


@@ -55,68 +54,7 @@
 		Assert.DoesNotContain("__version", text, StringComparison.Ordinal);
 		Assert.DoesNotContain("XamlComponentRegistry.Register", text, StringComparison.Ordinal);


…h (Tomas review) Follow-up to #36833 addressing Tomas Matousek's review comment on GeneratorHelpers (the content-hash algorithm choice). Once diagnostics classify a delta by the empty-vs-non-empty UpdateComponent() body (not by a stamped identity), nothing reads the generated __version field anymore — it became write-only. So rather than pick a different hash (xxHash128 etc.), remove the field and its hash entirely: - InitializeComponent no longer emits `private int __version` nor stamps it; drop the `__version = 0` reset on the legacy ResourceProvider2 fallback path. - Remove GeneratorHelpers.StableContentHash (its only consumer was the __version stamp). - Update the obsolete __version-era doc comments across the SourceGen writers. - Tests: drop the three __version-field assertions (Enabled_VersionField*/SetAtEndOfMethod), the CSharpExpression version-field assertion, and the __version parts of the determinism test; repurpose them to the surviving registration / reverse-transition behavior. No behavior change: __version was unused. XamlHotReloadState's internal Version counter (bookkeeping only, never emitted) is untouched — the broader static-cache concern Tomas raised is tracked separately. SourceGen.UnitTests: 460 green. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

src/Controls/src/SourceGen/UpdateComponentCodeWriter.cs:149

The XML doc comment here has a duplicated <summary> tag (/// <summary> twice). This produces malformed XML documentation (and can trigger CS1570/CS1584 warnings, which may break the build under warnings-as-errors). Remove the extra <summary> line so the comment has a single <summary> block.

	/// <summary>
	/// <summary>
	/// Generates the <c>UpdateComponent()</c> method body from a single baseline→current patch.

MauiBot

AI Review Summary

@StephaneDelcroix — new AI review results are available based on this last commit: 84e5dc0.

🗂️ Review Sessions — click to expand

🚦 Gate — Test Before & After Fix

Gate Result: ❌ FAILED

Platform: WINDOWS · Base: net11.0 · Merge base: c6dc61fa

🩺 Test does not reproduce the bug — ran the same in both states (PASS without fix, PASS with fix). The repro test is not exercising the issue. Strengthen the test before reviewing the fix.

Test	Without Fix (expect FAIL)	With Fix (expect PASS)
🧪 IncrementalHotReloadICTests `IncrementalHotReloadICTests`	❌ PASS — 337s	✅ PASS — 37s
🧪 XamlIncrementalHotReloadCSharpExpressionTests `XamlIncrementalHotReloadCSharpExpressionTests`	❌ PASS — 88s	✅ PASS — 30s
🧪 XamlIncrementalHotReloadE2ETests `XamlIncrementalHotReloadE2ETests`	❌ PASS — 87s	✅ PASS — 29s

🔴 Without fix — 🧪 IncrementalHotReloadICTests: PASS ❌ · 337s