fix: preserve registration state across FlushAsync calls

ClientScriptShim.FlushAsync was clearing _startupScripts, _scriptBlocks,
and _scriptIncludes after execution, causing Is*Registered methods to
return false. Web Forms preserves registration state for the full page
lifecycle. Added _flushed* HashSets to track executed keys so
IsStartupScriptRegistered, IsClientScriptBlockRegistered, and
IsClientScriptIncludeRegistered return true after flush.

Fixes: RegisterClientScriptInclude demo and Deduplication demo on the
ClientScriptShim sample page.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: csharpfritz

src/BlazorWebFormsComponents.Test/ClientScriptShimTests.cs

@@ -300,10 +300,11 @@ public async Task FlushAsync_ClearsQueuesAfterFlush()
 
 		await shim.FlushAsync(mockJs.Object);
 
-		// After flush, all queues should be empty
-		shim.IsStartupScriptRegistered(typeof(ClientScriptShimTests), "temp").ShouldBeFalse();
-		shim.IsClientScriptBlockRegistered(typeof(ClientScriptShimTests), "block").ShouldBeFalse();
-		shim.IsClientScriptIncludeRegistered("inc").ShouldBeFalse();
+		// After flush, queues are empty (no re-execution) but registration
+		// status persists — matching Web Forms page-lifecycle semantics.
+		shim.IsStartupScriptRegistered(typeof(ClientScriptShimTests), "temp").ShouldBeTrue();
+		shim.IsClientScriptBlockRegistered(typeof(ClientScriptShimTests), "block").ShouldBeTrue();
+		shim.IsClientScriptIncludeRegistered("inc").ShouldBeTrue();
 	}
 
 	[Fact]

src/BlazorWebFormsComponents/ClientScriptShim.cs

@@ -28,6 +28,9 @@ public class ClientScriptShim
 	private readonly Dictionary<string, string> _startupScripts = new();
 	private readonly Dictionary<string, string> _scriptBlocks = new();
 	private readonly Dictionary<string, string> _scriptIncludes = new();
+	private readonly HashSet<string> _flushedStartupScripts = new();
+	private readonly HashSet<string> _flushedScriptBlocks = new();
+	private readonly HashSet<string> _flushedScriptIncludes = new();
 
 	/// <summary>
 	/// Initializes a new instance of the <see cref="ClientScriptShim"/> class.
@@ -80,7 +83,8 @@ public void RegisterStartupScript(Type type, string key, string script)
 	/// <returns><c>true</c> if the script is registered; otherwise <c>false</c>.</returns>
 	public bool IsStartupScriptRegistered(Type type, string key)
 	{
-		return _startupScripts.ContainsKey(BuildKey(type, key));
+		var k = BuildKey(type, key);
+		return _startupScripts.ContainsKey(k) || _flushedStartupScripts.Contains(k);
 	}
 
 	// ─── Client Script Blocks ──────────────────────────────────────────
@@ -111,7 +115,8 @@ public void RegisterClientScriptBlock(Type type, string key, string script, bool
 	/// <returns><c>true</c> if the script block is registered; otherwise <c>false</c>.</returns>
 	public bool IsClientScriptBlockRegistered(Type type, string key)
 	{
-		return _scriptBlocks.ContainsKey(BuildKey(type, key));
+		var k = BuildKey(type, key);
+		return _scriptBlocks.ContainsKey(k) || _flushedScriptBlocks.Contains(k);
 	}
 
 	// ─── Client Script Includes ────────────────────────────────────────
@@ -149,7 +154,7 @@ public void RegisterClientScriptInclude(Type type, string key, string url)
 	/// <returns><c>true</c> if the include is registered; otherwise <c>false</c>.</returns>
 	public bool IsClientScriptIncludeRegistered(string key)
 	{
-		return _scriptIncludes.ContainsKey(key);
+		return _scriptIncludes.ContainsKey(key) || _flushedScriptIncludes.Contains(key);
 	}
 
 	// ─── Flush ─────────────────────────────────────────────────────────
@@ -188,6 +193,10 @@ public async Task FlushAsync(IJSRuntime jsRuntime)
 			await jsRuntime.InvokeVoidAsync("eval", loaderScript);
 		}
 
+		foreach (var key in _scriptBlocks.Keys) _flushedScriptBlocks.Add(key);
+		foreach (var key in _startupScripts.Keys) _flushedStartupScripts.Add(key);
+		foreach (var key in _scriptIncludes.Keys) _flushedScriptIncludes.Add(key);
+
 		_scriptBlocks.Clear();
 		_startupScripts.Clear();
 		_scriptIncludes.Clear();