Revert the sonic decl/impl split merge from main by chsienki · Pull Request #84831 · dotnet/roslyn

chsienki · 2026-08-10T18:38:13Z

Backs the features/sonic decl/impl split out of main to unblock insertion. Reverts the merge (#84778) and the commits that stacked on top of it and cannot stand without it.

What reverts

Merge/sonic into main #84778 Merge/sonic into main -- the whole feature body (reverted with -m 1, keeping pre-sonic main).
Keep a fallback component's derived tag helpers during discovery #84818 fallback child-content discovery fix -- patches sonic's fast/slow discovery, which no longer exists.
Restore public GetCSharpDocument() and GeneratedCode for runtime compilation #84813 restore GetCSharpDocument()/GeneratedCode -- these were re-added to shim sonic's API removal; reverting the merge restores the originals, so the shim would double-define them.
Always pass C# formatting options to Razor functions #84795 always pass C# formatting options -- edits CSharpFormattingOptionsHelper.cs, a file that only exists because of sonic.

What is kept

The other post-merge commits are independent of sonic and stay: arcade bumps, SDL param removal, CS8802, #84758 (syntax-tree sharing), and the two Razor features that merely shared files -- #84760 (unbound-attribute warnings) and #84764 (empty-outer-tag warning).

Preserving #84760 needed one manual resolution in UnresolvedAttributeIntermediateNode.cs: sonic added the CloneNode()/Clone() overrides and #84760 later added one property assignment inside CloneNode. The overrides are sonic infrastructure and go with the revert; #84760's IsDirectiveAttributeCandidate property and all its real usages are untouched.

Validation

Razor.slnf builds clean (compiler + all tooling projects, including the ones Always pass C# formatting options to Razor functions #84795 touched).
Microsoft.NET.Sdk.Razor.SourceGenerators.UnitTests: 215 passed.
Microsoft.AspNetCore.Razor.Language.UnitTests (component / tag helper / bind / unbound-attribute): 1593 passed -- confirms Add warnings for various unbound attributes in Razor #84760's kept feature still works.

Note

Reverting the merge means re-landing features/sonic later will need this revert itself reverted first -- expected for a back-out.

Microsoft Reviewers: Open in CodeFlow

…ery (dotnet#84818)" This reverts commit 24f9a0c.

…ime compilation (dotnet#84813)" This reverts commit 9f2738a.

…84795)" This reverts commit 59d60a4, reversing changes made to 8cd4945.

This reverts commit 5839d80, reversing changes made to a92cce0.

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azure-pipelines · 2026-08-10T18:38:43Z

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chsienki · 2026-08-10T18:47:30Z

/pr-val

github-actions · 2026-08-10T18:48:10Z

View PR Validation Run triggered by @chsienki

Parameters

Validation Type: pr-val
Pipeline ID: 8972
Pipeline Version: main
PR Number: 84831
Commit SHA: 967b0d3d06f812949fb015c16333726c66887c3f
Source Branch: revert/sonic-merge
Target Branch: main
Build ID: 14927709

…-15-langver * upstream/main: Unsafe evolution: allow await in unsafe context (dotnet#84616) Fix empty localization stage on non-main/release branches in official pipeline (dotnet#84845) Reorder stages for localization and build (dotnet#84841) Revert the sonic decl/impl split merge from main (dotnet#84831) AI Workflow - switch to use personal token instead of organizational (dotnet#84832) [main] Update dependencies from dotnet/arcade (dotnet#84819) Do not offer introduce parameter for incomplete calls (dotnet#84769)

This reverts commit 5864742.

…#84844) Re-lands the sonic decl/impl split (backed out in #84831 to unblock insertions) together with the slow-discovery perf work (#84808) and a new fix that removes the remaining cold-allocation regression on fallback components. ## Why this is safe to re-land now The split was reverted because a VS insertion showed a cold-allocation regression on fallback-heavy scenarios (Component Classification, cohosting completion) with no offsetting speed gain. This branch addresses the root cause rather than just re-applying the revert. ## What's here 1. **Un-revert** of #84831 -- restores the sonic merge and the fixes that landed on top of it (#84818 fallback child-content discovery, #84813 RZC public-API compat, #84795 formatting options). 2. **#84808** -- slow discovery resolves fallback types via the declaration table (`GetSymbolsWithName`) instead of a per-tree semantic model, and discovers only the fallback types rather than re-walking the whole augmented compilation. (Removed the +535 MB semantic-model regression.) 3. **Reuse the initial parse for fallback discovery** (new) -- the remaining regression. ## The new fix A fallback component (an `@inherits`/`@implements`/`@typeparam` header, or body markup the analysis can't route) can't be split, so its descriptor comes from discovery over an augmented compilation. Each fallback component was being processed **twice**: the generation engine's initial parse, then a freshly created declaration engine that **re-parsed the same source** just to produce a discoverable decl. For an app where nearly every component `@inherits` a base (MudBlazor, OrchardCore) every component is a fallback, so that second parse dominates cold discovery allocation. The split phase already builds the discoverable declaration surface for a *split* component from the nodes it just classified. This builds the same surface for a *fallback* component and stashes it on the document node; the generator lowers it in place -- reusing the initial parse -- instead of re-parsing through a separate engine. It's never emitted to pre-compilation (the bodiless type shell still fills that role for C# type resolution); only its syntax tree feeds slow discovery. The rare shapes with no render method or namespace keep the re-parse path. ## Measurements Cold source-generator allocation over 100 fallback components (in-memory A/B): | | Allocated | |---|---| | Pre-split baseline | 17.1 MB | | Sonic + #84808 (before this fix) | 19.6 MB | | **This branch** | **13.6 MB** | The fallback path is now **below** the pre-split baseline -- a genuine win, not break-even. ## Validation - `Microsoft.NET.Sdk.Razor.SourceGenerators.UnitTests`: 219 passed / 1 skipped (incl. #84818's fallback child-content test). - `Microsoft.AspNetCore.Razor.Language.UnitTests` (component / tag helper / split / bind / discovery / clone): 1672 passed. - Razor compiler builds clean. Draft pending the RPS + Speedometer insertion run. ###### Microsoft Reviewers: [Open in CodeFlow](https://microsoft.github.io/open-pr/?codeflow=https://github.com/dotnet/roslyn/pull/84844) --- ## Update: warm/interactive path fix (html-span completion) A matched-baseline Speedometer re-run showed the cold-discovery regressions gone but a smaller residual on **html-span completion in a component** (`CLR_BytesAllocated_devenv`) -- the interactive/warm path, a different signature than the cold source-generator work above. Root cause: the fallback decl incremental pipeline compared decls by **instance**, while the split-decl (`DeclSources`) fast path compares by **text**. A fallback component's decl is markup-free and checksum-suppressed, so a markup-only edit (every keystroke during completion) yields a byte-identical decl -- but the instance changed each run, invalidating the parse and, through the `Collect`, re-running slow discovery over *every* fallback component on each edit. Fix: compare fallback decls by text (`Text.ContentEquals`), mirroring the fast path. A markup-only edit now leaves the fallback decl `Unchanged`, keeping its parse and slow discovery cached. Measured (100 fallback components, warm re-run on a markup edit): | | warm alloc | |---|---| | Pre-split baseline | 0.41 MB | | Before this fix | 3.2 MB (~8x) | | **After this fix** | **0.42 MB** | Guarded by `IncrementalCompilation_WhenFallbackComponentMarkupChanges_SlowDiscoveryStaysCached` (verified to fail without the comparer). Full SG suite 220 passed / 1 skipped.

chsienki added 4 commits August 10, 2026 11:17

Revert "Keep a fallback component's derived tag helpers during discov…

f933c03

…ery (dotnet#84818)" This reverts commit 24f9a0c.

Revert "Restore public GetCSharpDocument() and GeneratedCode for runt…

2b35a58

…ime compilation (dotnet#84813)" This reverts commit 9f2738a.

Revert "Always pass C# formatting options to Razor functions (dotnet#…

51877b8

…84795)" This reverts commit 59d60a4, reversing changes made to 8cd4945.

Revert "Merge/sonic into main (dotnet#84778)"

967b0d3

This reverts commit 5839d80, reversing changes made to a92cce0.

Copilot AI lite review requested due to automatic review settings August 10, 2026 18:38

chsienki requested review from a team as code owners August 10, 2026 18:38

Copilot AI reviewed Aug 10, 2026

dotnet-policy-service Bot added VSCode Area-Razor labels Aug 10, 2026

davidwengier approved these changes Aug 10, 2026

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akhera99 approved these changes Aug 10, 2026

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JoeRobich approved these changes Aug 11, 2026

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JoeRobich merged commit 5864742 into dotnet:main Aug 11, 2026
27 checks passed

chsienki mentioned this pull request Aug 11, 2026

Re-land the sonic decl/impl split with fallback discovery parse reuse #84844

Merged

dotnet-maestro Bot mentioned this pull request Aug 12, 2026

[main] Source code updates from dotnet/roslyn dotnet/dotnet#8249

Merged

dotnet-bot mentioned this pull request Aug 13, 2026

[Automated] PRs inserted in VS build main-12112.60 #84875

Closed

chsienki added a commit that referenced this pull request Aug 21, 2026

Revert "Revert the sonic decl/impl split merge from main (#84831)"

79fcb6e

This reverts commit 5864742.

davidwengier mentioned this pull request Aug 24, 2026

Update roslyn to 5.11.0-1.26424.9 dotnet/vscode-csharp#9701

Merged

jjonescz added this to the 18.11 milestone Aug 25, 2026

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Revert the sonic decl/impl split merge from main - #84831

Revert the sonic decl/impl split merge from main#84831
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