Fixed Semantic Search with external data sources (ERI servers) (#1090)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/Tests/Tools/DataSourceUnreachableTests.cs

@@ -0,0 +1,50 @@
+using AIStudio.Settings.DataModel;
+using AIStudio.Tools.Services;
+
+namespace AIStudio.Tests.Tools;
+
+/// <summary>
+/// Checks which ERI data sources whose server could not be reached may still be named to a provider.
+/// </summary>
+/// <remarks>
+/// Such a data source is never searched, but Semantic Search tells the model about it, so that the
+/// model does not take its silence for finding nothing. Its server's requirements are unknown then,
+/// so only the security policy configured in AI Studio decides, and a provider which that policy
+/// keeps away must not even learn the name.
+/// </remarks>
+[TestFixture]
+public sealed class DataSourceUnreachableTests
+{
+    [TestCase(true)]
+    [TestCase(false)]
+    public void ADataSourceForAnyProviderMayBeNamed(bool usingTrustedProvider)
+    {
+        Assert.That(DataSourceService.MayBeNamedWhileUnreachable(ERISource(DataSourceSecurity.ALLOW_ANY), usingTrustedProvider), Is.True);
+    }
+
+    [Test]
+    public void ADataSourceForSelfHostedProvidersIsNamedOnlyToATrustedOne()
+    {
+        var source = ERISource(DataSourceSecurity.SELF_HOSTED);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(DataSourceService.MayBeNamedWhileUnreachable(source, usingTrustedProvider: true), Is.True);
+            Assert.That(DataSourceService.MayBeNamedWhileUnreachable(source, usingTrustedProvider: false), Is.False, "The data source would be refused to this provider if its server answered.");
+        });
+    }
+
+    [Test]
+    public void ADataSourceWithoutASecurityPolicyIsNeverNamed()
+    {
+        Assert.That(DataSourceService.MayBeNamedWhileUnreachable(ERISource(DataSourceSecurity.NOT_SPECIFIED), usingTrustedProvider: true), Is.False, "Better safe than sorry, as with a server which answers.");
+    }
+
+    private static DataSourceERI_V1 ERISource(DataSourceSecurity securityPolicy) => new()
+    {
+        Id = "33333333-3333-3333-3333-333333333333",
+        Name = "Intranet",
+        Type = DataSourceType.ERI_V1,
+        SecurityPolicy = securityPolicy,
+    };
+}