test(host): pin sequential clear-then-recompile contract of RoslynVirtualTagEvaluator (02/S12 baseline)

archreview/plans/R2-03-vt-failure-quality-plan.md.tasks.json

@@ -42,7 +42,7 @@
     {
       "id": "R2-03-T6",
       "subject": "S12 sequential pin: Evaluate_after_ClearCompiledScripts_recompiles_and_succeeds (green baseline the T8 retry-loop restructure must not regress)",
-      "status": "pending",
+      "status": "completed",
       "blockedBy": []
     },
     {

tests/Server/ZB.MOM.WW.OtOpcUa.Host.IntegrationTests/RoslynVirtualTagEvaluatorTests.cs

@@ -357,6 +357,29 @@ public sealed class RoslynVirtualTagEvaluatorTests
         CompiledCacheCount(sut).ShouldBe(0);
     }
 
+    /// <summary>02/S12 sequential pin: evaluating a compiled expression, clearing the cache, then
+    /// evaluating the SAME source again succeeds both times and leaves the cache with exactly one entry
+    /// (the recompile). This pins the clear-then-recompile contract the T8 retry-loop restructure must
+    /// not regress.</summary>
+    [Fact]
+    public void Evaluate_after_ClearCompiledScripts_recompiles_and_succeeds()
+    {
+        using var sut = new RoslynVirtualTagEvaluator(NullLogger<RoslynVirtualTagEvaluator>.Instance, NoOpScriptRoot());
+        const string expr = "return (int)ctx.GetTag(\"a\").Value + 1;";
+
+        var first = sut.Evaluate("vt-clear", expr, new Dictionary<string, object?> { ["a"] = 1 });
+        first.Success.ShouldBeTrue(first.Reason);
+        CompiledCacheCount(sut).ShouldBe(1);
+
+        sut.ClearCompiledScripts();
+        CompiledCacheCount(sut).ShouldBe(0);
+
+        var second = sut.Evaluate("vt-clear", expr, new Dictionary<string, object?> { ["a"] = 41 });
+        second.Success.ShouldBeTrue(second.Reason);
+        second.Value.ShouldBe(42);
+        CompiledCacheCount(sut).ShouldBe(1);
+    }
+
     /// <summary>Reads the count of the private compiled-script cache via reflection. The cache is a
     /// <c>CompiledScriptCache&lt;,&gt;</c> which exposes a <c>Count</c> property (not <c>ICollection</c>).</summary>
     private static int CompiledCacheCount(RoslynVirtualTagEvaluator sut)