fix(scriptanalysis): memoise ScriptTrustValidator verdicts by code hash for the default reference set (review 2026-10-21 04/P3)

2026-10-22 06:18:15 -04:00
parent ae1282ed9d
commit 8c935480fa
4 changed files with 170 additions and 2 deletions
@@ -0,0 +1,66 @@
+using ZB.MOM.WW.ScadaBridge.ScriptAnalysis;
+
+namespace ZB.MOM.WW.ScadaBridge.ScriptAnalysis.Tests;
+
+/// <summary>
+/// Review 2026-10-21 04/P3: <see cref="ScriptTrustValidator.FindViolations(string, IEnumerable{Microsoft.CodeAnalysis.MetadataReference})"/>
+/// is memoised by code hash for the default (policy) reference set, so the bundle
+/// importer's preview and apply passes — which call it with no change at their call
+/// sites — do not redo a full-framework semantic analysis per script. A cache hit
+/// returns the very same verdict instance, which is what these tests observe.
+/// </summary>
+public class ScriptTrustValidatorCacheTests
+{
+    /// <summary>Verifies that the same violating code analysed twice is served from the cache.</summary>
+    [Fact]
+    public void FindViolations_SameCodeTwice_SecondCallIsCacheHit()
+    {
+        var code = $"var x = System.IO.File.Exists(\"{Guid.NewGuid()}\");";
+        var first = ScriptTrustValidator.FindViolations(code);
+        var second = ScriptTrustValidator.FindViolations(code);
+
+        Assert.NotEmpty(second);
+        Assert.Same(first, second);   // pre-fix: a fresh list per call
+    }
+
+    /// <summary>Verifies that a clean verdict is cached too.</summary>
+    [Fact]
+    public void FindViolations_CleanCodeTwice_SecondCallIsCacheHit()
+    {
+        var code = $"var x = \"{Guid.NewGuid()}\".Length;";
+        var first = ScriptTrustValidator.FindViolations(code);
+        var second = ScriptTrustValidator.FindViolations(code);
+
+        Assert.Empty(second);
+        Assert.Same(first, second);
+    }
+
+    /// <summary>
+    /// Verifies that a call with extra references is never served from (or stored in)
+    /// the cache — extra references can change symbol resolution, so the verdict is a
+    /// pure function of the code only for the default reference set.
+    /// </summary>
+    [Fact]
+    public void FindViolations_WithExtraReferences_BypassesCache()
+    {
+        var code = $"var x = System.IO.File.Exists(\"{Guid.NewGuid()}\");";
+        var extra = new[] { Microsoft.CodeAnalysis.MetadataReference.CreateFromFile(typeof(ScriptCompileSurface).Assembly.Location) };
+        var a = ScriptTrustValidator.FindViolations(code, extra);
+        var b = ScriptTrustValidator.FindViolations(code, extra);
+        var cached = ScriptTrustValidator.FindViolations(code);
+
+        Assert.NotSame(a, b);
+        Assert.NotSame(a, cached);
+        Assert.NotSame(b, cached);
+    }
+
+    /// <summary>Verifies that the shared verdict cannot be mutated by a caller to poison the cache.</summary>
+    [Fact]
+    public void FindViolations_ReturnedList_IsReadOnly()
+    {
+        var code = $"var x = System.IO.File.Exists(\"{Guid.NewGuid()}\");";
+        var verdict = ScriptTrustValidator.FindViolations(code);
+        Assert.False(verdict is List<string>);
+        Assert.True(verdict is System.Collections.Generic.ICollection<string> { IsReadOnly: true });
+    }
+}