[Sonic] Support multiple C# documents in auto insert

[davidwengier]

Also moves logic from Workspaces up to Remote.

UPDATE: Seems I overlooked something in the on type formatting changes, which a test in this endpoint revealed, so the on type formatter got some changes too. Aside: I hate the on type formatter so much, and I want to delete so much code.

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

This PR refactors Razor auto-insert infrastructure so the provider logic lives in the Remote layer, and updates cohosting registration/tests accordingly, enabling C# auto-insert to work correctly when the mapped position targets different generated C# documents (decl vs impl).

Changes:

• Move Razor auto-insert provider contracts/exports into Microsoft.CodeAnalysis.Remote.Razor and remove the old Workspaces-based auto-insert service/types.
• Update RemoteAutoInsertService to select the correct generated C# document (decl/impl) and flow that choice into formatting/mapping.
• Simplify Cohost trigger-character registration by hardcoding the trigger sets, and add unit tests to keep cohost triggers in sync with OOP/Remote.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Razor/src/Razor/test/Microsoft.CodeAnalysis.Razor.CohostingShared.UnitTests/Endpoints/CohostOnAutoInsertEndpointTest.cs	Adds trigger-character sync tests; re-enables several previously skipped C# auto-insert tests.
src/Razor/src/Razor/test/Microsoft.CodeAnalysis.Razor.CohostingShared.UnitTests/AutoInsert/RazorOnAutoInsertProviderTestBase.cs	Updates tests to reference the new Remote auto-insert provider namespace.
src/Razor/src/Razor/test/Microsoft.CodeAnalysis.Razor.CohostingShared.UnitTests/AutoInsert/CloseTextTagOnAutoInsertProviderTest.cs	Updates using to new Remote provider namespace.
src/Razor/src/Razor/test/Microsoft.CodeAnalysis.Razor.CohostingShared.UnitTests/AutoInsert/AutoClosingTagOnAutoInsertProviderTest.cs	Updates using to new Remote provider namespace.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/AutoInsert/RemoteOnAutoInsertProviders.cs	Deletes now-unnecessary remote wrapper exports (providers are exported directly).
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/AutoInsert/RemoteAutoInsertService.cs	Moves Razor-provider resolution into Remote, adds decl/impl generated-doc support, and keeps trigger allowlists local.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/AutoInsert/OOPAutoInsertService.cs	Deletes old Workspaces-derived auto-insert service wrapper.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/AutoInsert/IOnAutoInsertProvider.cs	Moves the provider interface into the Remote namespace and inlines TriggerCharacter.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/AutoInsert/CloseTextTagOnAutoInsertProvider.cs	Moves provider into Remote namespace and adds MEF export attributes.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/AutoInsert/AutoClosingTagOnAutoInsertProvider.cs	Moves provider into Remote namespace and adds MEF export attributes.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/AutoInsert/IOnAutoInsertTriggerCharacterProvider.cs	Deletes obsolete Workspaces trigger-character-only contract.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/AutoInsert/IAutoInsertService.cs	Deletes obsolete Workspaces auto-insert service contract.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/AutoInsert/AutoInsertService.cs	Deletes obsolete Workspaces implementation of provider dispatch/trigger allowlists.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Razor.CohostingShared/OnAutoInsert/CohostOnAutoInsertTriggerCharacterProviders.cs	Deletes old cohost-only trigger providers (replaced by hardcoded trigger sets).
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Razor.CohostingShared/OnAutoInsert/CohostOnAutoInsertEndpoint.cs	Replaces MEF-imported trigger computation with static trigger arrays + test accessors.
src/Razor/src/Razor/src/Microsoft.CodeAnalysis.Razor.CohostingShared/Microsoft.CodeAnalysis.Razor.CohostingShared.projitems	Removes the deleted cohost trigger-provider file from the shared project items.

[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated no new comments.

[davidwengier]

Oh the test failure here is fun. So during typing, when the razor document looks like this:

@code {
    void TestMethod() {
        var x = """$$
    }
}

That document has no decl document, because the unterminated raw string literal eats the closing brace, so the code block is not a code block, so all of that goes in the impl document. As soon as auto insert runs, the document is now:

@code {
    void TestMethod() {
        var x = """$$"""
    }
}

That document has a correctly closed raw string literal, so has a code block, so has a decl document, and thats where the code is. So during formatting, the code we're trying to format moves from one document to the other. This is less than ideal. I legitimately don't know how to deal with this.