Add asset path metadata attributes

src/Components/Components/src/AcceptsAssetPathAttribute.cs

@@ -0,0 +1,46 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.Components;
+
+/// <summary>
+/// Declares an HTML element and attribute combination that accepts static asset-path expansion.
+/// </summary>
+/// <remarks>
+/// The Razor compiler discovers this metadata on public classes named <c>AssetPathAttributes</c>.
+/// </remarks>
+/// <example>
+/// <code>
+/// [AcceptsAssetPath("img", "src")]
+/// public static class AssetPathAttributes
+/// {
+/// }
+/// </code>
+/// </example>
+[AttributeUsage(AttributeTargets.Class, AllowMultiple = true, Inherited = true)]
+public sealed class AcceptsAssetPathAttribute : Attribute
+{
+    /// <summary>
+    /// Initializes a new instance of <see cref="AcceptsAssetPathAttribute"/>.
+    /// </summary>
+    /// <param name="elementName">The HTML element name.</param>
+    /// <param name="attributeName">The HTML attribute name.</param>
+    public AcceptsAssetPathAttribute(string elementName, string attributeName)
+    {
+        ArgumentNullException.ThrowIfNull(elementName);
+        ArgumentNullException.ThrowIfNull(attributeName);
+
+        ElementName = elementName;
+        AttributeName = attributeName;
+    }
+
+    /// <summary>
+    /// Gets the HTML element name.
+    /// </summary>
+    public string ElementName { get; }
+
+    /// <summary>
+    /// Gets the HTML attribute name.
+    /// </summary>
+    public string AttributeName { get; }
+}

src/Components/Components/src/AssetPathAttribute.cs

@@ -0,0 +1,22 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.Components;
+
+/// <summary>
+/// Indicates that a component parameter accepts a static asset path that the Razor compiler can expand.
+/// </summary>
+/// <remarks>
+/// This attribute is valid only on properties that are also marked with <see cref="ParameterAttribute"/>.
+/// </remarks>
+/// <example>
+/// <code>
+/// [Parameter]
+/// [AssetPath]
+/// public string? Source { get; set; }
+/// </code>
+/// </example>
+[AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)]
+public sealed class AssetPathAttribute : Attribute
+{
+}

src/Components/Components/src/PublicAPI.Unshipped.txt

@@ -1,4 +1,10 @@
 #nullable enable
+Microsoft.AspNetCore.Components.AcceptsAssetPathAttribute
+Microsoft.AspNetCore.Components.AcceptsAssetPathAttribute.AcceptsAssetPathAttribute(string! elementName, string! attributeName) -> void
+Microsoft.AspNetCore.Components.AcceptsAssetPathAttribute.AttributeName.get -> string!
+Microsoft.AspNetCore.Components.AcceptsAssetPathAttribute.ElementName.get -> string!
+Microsoft.AspNetCore.Components.AssetPathAttribute
+Microsoft.AspNetCore.Components.AssetPathAttribute.AssetPathAttribute() -> void
 Microsoft.AspNetCore.Components.CacheBehavior
 Microsoft.AspNetCore.Components.CacheBehavior.Rerender = 0 -> Microsoft.AspNetCore.Components.CacheBehavior
 Microsoft.AspNetCore.Components.CacheBehavior.Throw = 1 -> Microsoft.AspNetCore.Components.CacheBehavior

src/Components/Web/src/PublicAPI.Unshipped.txt

@@ -1,4 +1,5 @@
 #nullable enable
+Microsoft.AspNetCore.Components.Web.AssetPathAttributes
 Microsoft.AspNetCore.Components.Web.EnvironmentView
 Microsoft.AspNetCore.Components.Web.EnvironmentView.ChildContent.get -> Microsoft.AspNetCore.Components.RenderFragment?
 Microsoft.AspNetCore.Components.Web.EnvironmentView.ChildContent.set -> void

src/Components/Web/src/Web/AssetPathAttributes.cs

@@ -0,0 +1,24 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace Microsoft.AspNetCore.Components.Web;
+
+/// <summary>
+/// Infrastructure for the discovery of HTML attributes that accept static asset-path expansion.
+/// </summary>
+/// <remarks>
+/// To extend the supported element and attribute combinations, define a public class named
+/// <c>AssetPathAttributes</c> and annotate it with <see cref="AcceptsAssetPathAttribute"/>.
+/// </remarks>
+[AcceptsAssetPath("audio", "src")]
+[AcceptsAssetPath("img", "src")]
+[AcceptsAssetPath("input", "src")]
+[AcceptsAssetPath("link", "href")]
+[AcceptsAssetPath("script", "src")]
+[AcceptsAssetPath("source", "src")]
+[AcceptsAssetPath("track", "src")]
+[AcceptsAssetPath("video", "poster")]
+[AcceptsAssetPath("video", "src")]
+public static class AssetPathAttributes
+{
+}