Add opt-in ~/ asset-path expansion for Razor components (compiler) by chsienki · Pull Request #84796 · dotnet/roslyn

chsienki · 2026-08-06T23:11:50Z

This is the Roslyn (Razor compiler) half of the ~/ asset-path expansion feature proposed in dotnet/aspnetcore#68229.

Note

The feature is inert until the runtime ships [AssetPath] / [AcceptsAssetPath] / the AssetPathAttributes convention type in Microsoft.AspNetCore.Components. The tests stub those attributes, so the compiler builds and its tests pass today, but end-to-end behavior depends on the coordinated runtime + SDK changes landing.

What this does

Adds opt-in, compile-time expansion of literal ~/-prefixed attribute values in .razor files into Assets[@"..."] expressions, so <img src="~/images/logo.png"> behaves like <img src="@Assets[@"images/logo.png"]"> -- only where the target has explicitly opted in:

HTML element attributes whose (element, attribute) pair the runtime declares via [AcceptsAssetPath(elementName, attributeName)] on a public AssetPathAttributes convention type (built-in allowlist: img[src], link[href], script[src]).
Component parameters marked [AssetPath] (honored only on string parameters).

When nothing is opted in, ~/ is left untouched -- existing markup is unaffected. There is no ambient behavior, so no MSBuild opt-out is needed.

Design

AcceptsAssetPathTagHelperProducer discovers the AssetPathAttributes convention type during tag-helper discovery and emits carrier TagHelperDescriptors (AssetPathMetadata) with no tag-matching rules -- they exist purely to carry the allowlist to the lowering pass. [AssetPath] on a string component parameter is recorded as PropertyMetadata.AcceptsAssetPath.
ComponentTildePathPass (an IRazorOptimizationPass, Order 75) reads the full discovered tag-helper set via ITagHelperFeature (compilation-global, not scoped to the document's in-scope tag helpers), builds an element -> attributes allowlist once per engine, and rewrites only opted-in single-literal ~/ values. Gated on Razor language version 11.0.

Diagnostics

RZ10029 (warning): a ~/ literal is mixed with dynamic content on an opted-in attribute, so it can't be expanded.
RZ10030 (warning): [AssetPath] is applied to a non-string parameter; the opt-in is ignored (expanding ~/ would yield an Assets[...] string that isn't assignable).

Commits

Add asset-path metadata types (enums + AssetPathMetadata + PropertyMetadata.AcceptsAssetPath).
Discover [AssetPath] / [AcceptsAssetPath] declarations (producer + registration; RZ10030 for non-string [AssetPath]).
Expand opted-in ~/ literals via ComponentTildePathPass (+ RZ10029).
Tests and baselines.
Docs (docs/razor/tilde-path-expansion.md).

Each commit builds and is test-green.

Testing

ComponentCodeGenerationTestBase TildePath_* cases cover opted-in expansion (HTML + component params) and the backward-compatible non-expansion cases: not opted in, attribute outside the allowlist, bare ~, explicit @(), pre-11.0 language version, mixed content (RZ10029), and non-string [AssetPath] (RZ10030).

Introduce the descriptor and property metadata the Razor compiler uses to recognize opt-in asset-path expansion, ahead of the discovery and lowering that consume them: - AssetPathMetadata carries a single (element, attribute) pair declared via [AcceptsAssetPath], surfaced as a tag-helper descriptor. - PropertyMetadata.AcceptsAssetPath marks a component parameter opted in via [AssetPath]. - New AssetPath / AcceptsAssetPath members on the TagHelperKind, MetadataKind, and TagHelperProducerKind enums, with the component-kind range extended to include the new tag-helper kind. - ComponentsApi gains the well-known metadata names for the [AssetPath] and [AcceptsAssetPath] attributes and the AssetPathAttributes convention type. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: ef56ab10-2d3d-4e55-a318-3d03bfbdd713

azure-pipelines · 2026-08-11T17:40:29Z

Azure Pipelines: Successfully started running 2 pipeline(s). There may be pipelines that require an authorized user to comment /azp run to run.

Copilot

Pull request overview

Adds compiler-side support in the Razor component pipeline for opt-in expansion of literal attribute values starting with ~/ into Assets[...] expressions, using runtime-declared opt-in metadata ([AcceptsAssetPath] for specific HTML element/attribute pairs and [AssetPath] for component parameters). This lives in the Razor compiler layer (src/Razor/src/Compiler/...) and is gated on Razor language version 11.0.

Changes:

Introduces AcceptsAssetPathTagHelperProducer + AssetPathMetadata carriers and PropertyMetadata.AcceptsAssetPath to surface opt-in metadata into lowering/optimization.
Adds ComponentTildePathPass (Order 75) to rewrite opted-in ~/... literals into Assets[@"..."] tokens and emit warning RZ10029 for mixed content.
Adds extensive baseline coverage in ComponentCodeGenerationTestBase and new documentation describing the feature.

Reviewed changes

Copilot reviewed 99 out of 99 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/TagHelpers/Producers/TagHelperProducerKind.cs	Adds producer kind for `[AcceptsAssetPath]` discovery.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/TagHelpers/Producers/ComponentTagHelperProducer.cs	Records `[AssetPath]` on component parameters as `AcceptsAssetPath` metadata.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/TagHelpers/Producers/AcceptsAssetPathTagHelperProducer.Factory.cs	Factory to enable producer only when runtime attribute type is present.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/TagHelpers/Producers/AcceptsAssetPathTagHelperProducer.cs	Produces carrier tag helpers containing `(element, attribute)` allowlist metadata.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/TagHelperKindExtensions.cs	Extends “component kinds” range to include `AssetPath`.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/TagHelperKind.cs	Adds new `TagHelperKind.AssetPath` value.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/RazorProjectEngine.cs	Registers `ComponentTildePathPass` in the component feature set.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/MetadataObject.cs	Adds `MetadataKind.AssetPath` for new metadata record type.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Components/PropertyMetadata.cs	Adds `AcceptsAssetPath` flag to component-parameter metadata and checksum.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Components/ComponentTildePathPass.cs	Implements the rewrite pass and mixed-content diagnostic emission.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Components/ComponentsApi.cs	Adds metadata-name constants for new runtime attributes and `ComponentBase.Assets`.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Components/ComponentDiagnosticFactory.cs	Introduces warning descriptor + factory for RZ10029 (mixed content).
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Components/AssetPathMetadata.cs	New metadata record for `(element, attribute)` allowlist entries.
src/Razor/src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/CSharp/CompilerFeatures.cs	Registers `AcceptsAssetPathTagHelperProducer` for discovery.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_WithSlash/TestComponent.ir.txt	New baseline: IR for opted-in `~/` expansion (HTML).
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_WithSlash/TestComponent.decl.ir.txt	New baseline: declaration IR for `TildePath_WithSlash`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_WithSlash/TestComponent.decl.codegen.cs	New baseline: declaration codegen for `TildePath_WithSlash`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_WithSlash/TestComponent.codegen.cs	New baseline: codegen for `TildePath_WithSlash`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_WithSlash/TestComponent.builder.txt	New baseline: render-tree builder output for `TildePath_WithSlash`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NoTilde/TestComponent.ir.txt	New baseline: non-expansion when no tilde.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NoTilde/TestComponent.decl.ir.txt	New baseline: declaration IR for `TildePath_NoTilde`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NoTilde/TestComponent.decl.codegen.cs	New baseline: declaration codegen for `TildePath_NoTilde`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NoTilde/TestComponent.codegen.cs	New baseline: codegen for `TildePath_NoTilde`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NoTilde/TestComponent.builder.txt	New baseline: builder output for `TildePath_NoTilde`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NotExpandedBeforeLanguageVersion11/TestComponent.ir.txt	New baseline: version-gated non-expansion (pre-11.0).
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NotExpandedBeforeLanguageVersion11/TestComponent.decl.ir.txt	New baseline: declaration IR for version-gated case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NotExpandedBeforeLanguageVersion11/TestComponent.decl.codegen.cs	New baseline: declaration codegen for version-gated case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NotExpandedBeforeLanguageVersion11/TestComponent.codegen.cs	New baseline: codegen for version-gated case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_NotExpandedBeforeLanguageVersion11/TestComponent.builder.txt	New baseline: builder output for version-gated case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MultipleElements/TestComponent.ir.txt	New baseline: multiple opted-in HTML attributes.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MultipleElements/TestComponent.decl.ir.txt	New baseline: declaration IR for multiple-elements case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MultipleElements/TestComponent.decl.codegen.cs	New baseline: declaration codegen for multiple-elements case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MultipleElements/TestComponent.codegen.cs	New baseline: codegen for multiple-elements case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MultipleElements/TestComponent.builder.txt	New baseline: builder output for multiple-elements case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MixedContent/TestComponent.mappings.txt	New baseline: source mappings for mixed-content scenario.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MixedContent/TestComponent.ir.txt	New baseline: IR showing mixed literal/expression attribute content.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MixedContent/TestComponent.diagnostics.txt	New baseline: RZ10029 warning for mixed content.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MixedContent/TestComponent.decl.ir.txt	New baseline: declaration IR for mixed-content case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MixedContent/TestComponent.decl.codegen.cs	New baseline: declaration codegen for mixed-content case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MixedContent/TestComponent.codegen.cs	New baseline: codegen for mixed-content case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_MixedContent/TestComponent.builder.txt	New baseline: builder output for mixed-content case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement/TestComponent.ir.txt	New baseline: HTML opted-in expansion (`img[src]`).
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement/TestComponent.decl.ir.txt	New baseline: declaration IR for HTML opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement/TestComponent.decl.codegen.cs	New baseline: declaration codegen for HTML opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement/TestComponent.codegen.cs	New baseline: codegen for HTML opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement/TestComponent.builder.txt	New baseline: builder output for HTML opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement_NotOptedIn/TestComponent.ir.txt	New baseline: non-expansion when HTML allowlist isn’t present.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement_NotOptedIn/TestComponent.decl.ir.txt	New baseline: declaration IR for HTML not-opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement_NotOptedIn/TestComponent.decl.codegen.cs	New baseline: declaration codegen for HTML not-opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement_NotOptedIn/TestComponent.codegen.cs	New baseline: codegen for HTML not-opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_HtmlElement_NotOptedIn/TestComponent.builder.txt	New baseline: builder output for HTML not-opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ExplicitExpressionNotExpanded/TestComponent.mappings.txt	New baseline: mappings for explicit-expression escape case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ExplicitExpressionNotExpanded/TestComponent.ir.txt	New baseline: IR for explicit-expression escape case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ExplicitExpressionNotExpanded/TestComponent.decl.ir.txt	New baseline: declaration IR for explicit-expression escape case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ExplicitExpressionNotExpanded/TestComponent.decl.codegen.cs	New baseline: declaration codegen for explicit-expression escape case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ExplicitExpressionNotExpanded/TestComponent.codegen.cs	New baseline: codegen for explicit-expression escape case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ExplicitExpressionNotExpanded/TestComponent.builder.txt	New baseline: builder output for explicit-expression escape case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPathWithSlash/TestComponent.ir.txt	New baseline: no expansion for `~/` with empty path.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPathWithSlash/TestComponent.decl.ir.txt	New baseline: declaration IR for empty-path-with-slash case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPathWithSlash/TestComponent.decl.codegen.cs	New baseline: declaration codegen for empty-path-with-slash case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPathWithSlash/TestComponent.codegen.cs	New baseline: codegen for empty-path-with-slash case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPathWithSlash/TestComponent.builder.txt	New baseline: builder output for empty-path-with-slash case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPath/TestComponent.ir.txt	New baseline: no expansion for bare `~`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPath/TestComponent.decl.ir.txt	New baseline: declaration IR for bare-tilde case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPath/TestComponent.decl.codegen.cs	New baseline: declaration codegen for bare-tilde case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPath/TestComponent.codegen.cs	New baseline: codegen for bare-tilde case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_EmptyPath/TestComponent.builder.txt	New baseline: builder output for bare-tilde case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam/TestComponent.mappings.txt	New baseline: mappings for component parameter expansion.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam/TestComponent.ir.txt	New baseline: IR for component parameter expansion.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam/TestComponent.decl.ir.txt	New baseline: declaration IR for component parameter expansion.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam/TestComponent.decl.codegen.cs	New baseline: declaration codegen for component parameter expansion.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam/TestComponent.codegen.cs	New baseline: codegen for component parameter expansion.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam/TestComponent.builder.txt	New baseline: builder output for component parameter expansion.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam_NotOptedIn/TestComponent.mappings.txt	New baseline: mappings for component param non-expansion case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam_NotOptedIn/TestComponent.ir.txt	New baseline: IR for component param non-expansion case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam_NotOptedIn/TestComponent.decl.ir.txt	New baseline: declaration IR for component param non-expansion case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam_NotOptedIn/TestComponent.decl.codegen.cs	New baseline: declaration codegen for component param non-expansion case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam_NotOptedIn/TestComponent.codegen.cs	New baseline: codegen for component param non-expansion case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_ComponentParam_NotOptedIn/TestComponent.builder.txt	New baseline: builder output for component param non-expansion case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BareTildeNotExpanded/TestComponent.ir.txt	New baseline: bare `~path` does not expand.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BareTildeNotExpanded/TestComponent.decl.ir.txt	New baseline: declaration IR for bare-tilde case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BareTildeNotExpanded/TestComponent.decl.codegen.cs	New baseline: declaration codegen for bare-tilde case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BareTildeNotExpanded/TestComponent.codegen.cs	New baseline: codegen for bare-tilde case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BareTildeNotExpanded/TestComponent.builder.txt	New baseline: builder output for bare-tilde case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BackslashInPath/TestComponent.ir.txt	New baseline: expansion preserves backslashes via verbatim literal.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BackslashInPath/TestComponent.decl.ir.txt	New baseline: declaration IR for backslash case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BackslashInPath/TestComponent.decl.codegen.cs	New baseline: declaration codegen for backslash case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BackslashInPath/TestComponent.codegen.cs	New baseline: codegen for backslash case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_BackslashInPath/TestComponent.builder.txt	New baseline: builder output for backslash case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_AttributeNotOptedIn/TestComponent.ir.txt	New baseline: non-expansion for attributes outside allowlist.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_AttributeNotOptedIn/TestComponent.decl.ir.txt	New baseline: declaration IR for attribute-not-opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_AttributeNotOptedIn/TestComponent.decl.codegen.cs	New baseline: declaration codegen for attribute-not-opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_AttributeNotOptedIn/TestComponent.codegen.cs	New baseline: codegen for attribute-not-opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/TestFiles/IntegrationTests/ComponentCodeGenerationTest/TildePath_AttributeNotOptedIn/TestComponent.builder.txt	New baseline: builder output for attribute-not-opted-in case.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/RazorProjectEngineTest.cs	Updates default feature list assertions to include `ComponentTildePathPass`.
src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/IntegrationTests/ComponentCodeGenerationTestBase.cs	Adds test region, stubs, and integration tests for tilde expansion scenarios.
docs/razor/tilde-path-expansion.md	New end-to-end documentation describing syntax, opt-in model, diagnostics, and implementation.
.github/memory/testing/razor.md	Updates Razor test guidance (baselines and two-phase compilation notes).
.github/instructions/Razor.instructions.md	Documents the “runtime-declared attribute list” pattern for Razor compiler work.

Suppressed comments (2)

docs/razor/tilde-path-expansion.md:22

The docs’ generated C# snippet uses Assets["images/logo.png"], but the compiler emits a verbatim literal (Assets[@"images/logo.png"]). The snippet should match actual output (including the @).

Both produce the same generated C#:

```csharp
__builder.AddAttribute(1, "src", Assets["images/logo.png"]);

**docs/razor/tilde-path-expansion.md:62**
* In the Syntax table, the “Generated C#” column shows `Assets["..."]`, but the compiler emits verbatim literals (`Assets[@"..."]`). Updating the table keeps it consistent with actual codegen and with the backslash-handling rationale later in the doc.

Input	Generated C#	Notes
`src="~/images/logo.png"`	`Assets["images/logo.png"]`	Standard form
`src="~images/logo.png"`	`"~images/logo.png"` (literal)	No slash, no transformation
`src="~/~images.png"`	`Assets["~images.png"]`	Only leading `~/` is special

</details>

Read the runtime's asset-path opt-in metadata during tag-helper discovery: - AcceptsAssetPathTagHelperProducer finds the public AssetPathAttributes convention type and emits one carrier tag-helper descriptor per declared (element, attribute) pair, following the BindAttributes / EventHandlers model. The descriptors declare no tag-matching rules; they exist only to carry the allowlist to the lowering pass. - ComponentTagHelperProducer records [AssetPath] on a component parameter as PropertyMetadata.AcceptsAssetPath. - CompilerFeatures registers the new producer. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: ef56ab10-2d3d-4e55-a318-3d03bfbdd713

Rewrite literal ~/-prefixed attribute values into Assets["..."] expressions, but only where the target has opted in: - HTML element attributes whose (element, attribute) pair appears in the discovered [AcceptsAssetPath] allowlist. - Component parameters whose bound attribute has PropertyMetadata.AcceptsAssetPath. The pass reads the full discovered tag-helper set from ITagHelperFeature so the allowlist is compilation-global rather than scoped to the document's in-scope tag helpers. Mixed literal/expression content on an opted-in attribute is reported as RZ10025. Expansion is gated on Razor language version 11.0. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: ef56ab10-2d3d-4e55-a318-3d03bfbdd713

Cover opted-in expansion for HTML elements and component parameters, plus the backward-compatible cases where ~/ is left untouched: no [AssetPath], an attribute outside the allowlist, bare ~, explicit @() expressions, pre-11.0 language version, and mixed content (RZ10025). Baselines are generated with: dotnet test src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/Microsoft.AspNetCore.Razor.Language.UnitTests.csproj /p:GenerateBaselines=true Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: ef56ab10-2d3d-4e55-a318-3d03bfbdd713

Add the feature design doc and record the discovery/allowlist pattern and the baseline-regeneration workflow in the agent knowledge base. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: ef56ab10-2d3d-4e55-a318-3d03bfbdd713

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chsienki · 2026-08-11T19:54:32Z

/azp run roslyn-CI

azure-pipelines · 2026-08-11T19:54:47Z

Azure Pipelines: Successfully started running 1 pipeline(s).

davidwengier · 2026-08-12T02:08:00Z

+            }
+
+            // Verbatim string literal: backslashes (common in paths) stay literal and only embedded
+            // quotes need doubling. Source is null -- synthetic code with no .razor mapping.


This is interesting. Tooling supports Go To Def on file paths in string literals, we will have to follow up here because the existing system won't work without mapping. We probably can't even use an enhanced line pragma to map part of the string, right, because of the trimmed ~/?

I opened #84945 to track this

- Convert the AssetPathMetadata and ComponentTildePathPass header comments to <summary> doc comments, and move the BuildAllowedElementAttributes note inside the method body. - Use a list pattern in GetSingleLiteralToken. - Add TildePath_MultipleAttributesSameElement covering two opted-in attributes on a single element (img srcset + src), and opt img[srcset] into the test stub. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: ef56ab10-2d3d-4e55-a318-3d03bfbdd713

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Suppressed comments (2)

src/Razor/src/Compiler/Microsoft.AspNetCore.Razor.Language/test/IntegrationTests/ComponentCodeGenerationTestBase.cs:13489

Comment says the backslash should be "escaped" in generated C#, but the generated code uses a verbatim string literal (e.g., @"images\logo.png"), so backslashes are preserved as-is. Update the comment to match the actual behavior being asserted by the baselines.

        // Assert - backslash should be escaped in the generated C# string literal

docs/razor/tilde-path-expansion.md:49

This public doc includes internal/non-public references (Azure DevOps board entry and rows marked "Private"), which aren’t actionable for external contributors and will quickly go stale. Consider removing these rows (or replacing them with public links) and keeping only publicly accessible references.

| aspnetcore#68229 | https://github.com/dotnet/aspnetcore/issues/68229 | **Canonical proposal** -- authoritative API names, HTML allowlist, and cross-repo plan |
| aspnetcore#56076 | https://github.com/dotnet/aspnetcore/issues/56076 | Runtime APIs that introduced `Assets` indexer |
| AzDO#2623010 | DevDiv Razor Experiences board | Internal tracking work item |
| Razor-Language-Design#10 | Private | Language design discussion |
| aspnet/specs#769 | Private | Javier's design note |

Youssef1313 · 2026-09-01T08:53:27Z


+            // [AssetPath] enables ~/ expansion only for string parameters. On any other type the
+            // rewritten Assets[...] value wouldn't be assignable, so ignore the opt-in and warn.
+            if (property.GetAttributes().Any(static a => a.HasFullName(ComponentsApi.AssetPathAttribute.MetadataName)))


@chsienki This doesn't consider inheritance right?

The attribute per the approved API in dotnet/aspnetcore#68237 uses Inherited = true

I do believe that either we should change it to Inherited = false or otherwise make sure that Razor respects inheritance correctly to avoid confusion.

`AssetPathAttribute` has `Inherited = true`, but component parameter discovery only inspects attributes declared directly on the selected property. An override that redeclares `[Parameter]` therefore loses the base property's asset-path opt-in and leaves `~/` literals unexpanded. Follow the `OverriddenProperty` chain when resolving `[AssetPath]`. This preserves attribute inheritance for overrides without applying the opt-in to hidden properties. Add an integration baseline covering a base virtual parameter with `[AssetPath]` and a derived override that redeclares only `[Parameter]`. Addresses #84796 (comment) ###### Microsoft Reviewers: [Open in CodeFlow](https://microsoft.github.io/open-pr/?codeflow=https://github.com/dotnet/roslyn/pull/85171) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: dd15ad81-c929-4d0c-91de-354c0c777533

dotnet-policy-service Bot added the Area-Razor label Aug 6, 2026

chsienki force-pushed the features/tilde-path-expansion branch 3 times, most recently from 4b70ac9 to 5bf0f6c Compare August 10, 2026 17:49

chsienki force-pushed the features/tilde-path-expansion branch from 5bf0f6c to 87fe605 Compare August 11, 2026 17:40

chsienki marked this pull request as ready for review August 11, 2026 17:40

chsienki requested a review from a team as a code owner August 11, 2026 17:40

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Comment thread ....CodeAnalysis.Razor.Compiler/src/Language/TagHelpers/Producers/ComponentTagHelperProducer.cs

Comment thread docs/razor/tilde-path-expansion.md

Comment thread .../Microsoft.CodeAnalysis.Razor.Compiler/src/Language/Components/ComponentDiagnosticFactory.cs

chsienki and others added 4 commits August 11, 2026 11:12

Copilot AI review requested due to automatic review settings August 11, 2026 18:16

chsienki force-pushed the features/tilde-path-expansion branch from 87fe605 to d0f1c32 Compare August 11, 2026 18:16

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davidwengier approved these changes Aug 12, 2026

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chsienki mentioned this pull request Aug 18, 2026

Go To Definition (and span-based tooling) on Razor ~/ asset paths needs source mapping #84945

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chsienki merged commit 6b1f505 into dotnet:main Aug 18, 2026
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This was referenced Aug 19, 2026

[main] Source code updates from dotnet/roslyn dotnet/dotnet#8427

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[release/11.0.1xx] Source code updates from dotnet/roslyn dotnet/dotnet#8411

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davidwengier mentioned this pull request Aug 24, 2026

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

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jjonescz added this to the 18.11 milestone Aug 25, 2026

chsienki mentioned this pull request Aug 26, 2026

Provide IntelliSense for ~/ asset paths in Razor components #85058

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Youssef1313 mentioned this pull request Sep 1, 2026

[API Proposal]: Add asset-path metadata for Razor expansion dotnet/aspnetcore#68237

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chsienki mentioned this pull request Sep 5, 2026

Honor inherited AssetPath attributes on component parameters #85171

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chsienki commented Aug 6, 2026 •

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