review(Driver.OpcUaClient): release browse continuation point on cancel
Re-review at 7286d320. -016: BrowseRecursiveAsync now releases the server-side continuation
point on OperationCanceledException (BrowseNext releaseContinuationPoints:true) before
rethrowing (resolves the Browser-002 cross-cutting leak) + TDD.
This commit is contained in:
Joseph Doherty
+226
@@ -0,0 +1,226 @@
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using Moq;
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using Opc.Ua;
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using Opc.Ua.Client;
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using Shouldly;
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using Xunit;
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using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
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namespace ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient.Tests;
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/// <summary>
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/// Regression coverage for Driver.OpcUaClient-016: when the caller cancels during
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/// the <c>BrowseNextAsync</c> pagination loop inside <c>BrowseRecursiveAsync</c>, the
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/// server-side continuation point must be released via
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/// <c>BrowseNextAsync(releaseContinuationPoints: true)</c> before the
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/// <see cref="OperationCanceledException"/> propagates. Without the release the server
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/// retains the cursor open until the session is closed (a resource leak). This is the
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/// same pattern the Browser subagent recorded as Driver.OpcUaClient.Browser-002 and
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/// noted also exists in the runtime pagination loop.
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/// </summary>
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[Trait("Category", "Unit")]
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public sealed class OpcUaClientContinuationPointReleaseTests
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{
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// A fake non-empty continuation point so the pagination loop can be triggered.
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private static readonly byte[] FakeContinuationPoint = [0x01, 0x02, 0x03];
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/// <summary>
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/// Builds a loose <see cref="ISession"/> mock where:
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/// <list type="bullet">
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/// <item><c>BrowseAsync</c> returns a result with one Object-class child and a
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/// non-empty continuation point so the pagination loop is entered.</item>
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/// <item><c>BrowseNextAsync(releaseContinuationPoints: false)</c> throws
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/// <see cref="OperationCanceledException"/> — simulating cancellation mid-page.</item>
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/// <item><c>BrowseNextAsync(releaseContinuationPoints: true)</c> returns an empty
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/// response — the release call the fixed driver should issue before rethrowing.</item>
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/// </list>
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/// </summary>
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private static Mock<ISession> BuildCancellingSessionMock()
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{
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var mock = new Mock<ISession>(MockBehavior.Loose);
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mock.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext());
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mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
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// BrowseAsync — return one Object child plus a non-empty continuation point so
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// the pagination loop is entered. The child node is irrelevant; the loop is
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// what matters.
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var firstRef = new ReferenceDescription
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{
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NodeId = new ExpandedNodeId(new NodeId(1000, 2), "opc.tcp://test"),
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BrowseName = new QualifiedName("TestObject", 2),
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DisplayName = new LocalizedText("TestObject"),
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NodeClass = NodeClass.Object,
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};
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var browseResult = new BrowseResult
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{
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ContinuationPoint = FakeContinuationPoint,
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References = new ReferenceDescriptionCollection { firstRef },
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};
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var browseResp = new BrowseResponse
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{
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ResponseHeader = new ResponseHeader(),
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Results = new BrowseResultCollection { browseResult },
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DiagnosticInfos = new DiagnosticInfoCollection(),
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};
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mock.Setup(s => s.BrowseAsync(
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It.IsAny<RequestHeader>(),
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It.IsAny<ViewDescription>(),
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It.IsAny<uint>(),
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It.IsAny<BrowseDescriptionCollection>(),
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It.IsAny<CancellationToken>()))
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.ReturnsAsync(browseResp);
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// BrowseNextAsync(release=false) — pagination call: throw cancellation.
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mock.Setup(s => s.BrowseNextAsync(
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It.IsAny<RequestHeader>(),
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It.Is<bool>(release => !release),
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It.IsAny<ByteStringCollection>(),
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It.IsAny<CancellationToken>()))
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.ThrowsAsync(new OperationCanceledException("ct cancelled during BrowseNext"));
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// BrowseNextAsync(release=true) — the release call the fixed driver must make.
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// BrowseNextResponse.Results shares BrowseResult (same as BrowseResponse.Results);
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// there is no separate BrowseNextResult type in the OPC UA SDK.
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var emptyReleaseResult = new BrowseResult
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{
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ContinuationPoint = Array.Empty<byte>(),
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References = new ReferenceDescriptionCollection(),
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};
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var releaseResp = new BrowseNextResponse
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{
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ResponseHeader = new ResponseHeader(),
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Results = new BrowseResultCollection { emptyReleaseResult },
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DiagnosticInfos = new DiagnosticInfoCollection(),
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};
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mock.Setup(s => s.BrowseNextAsync(
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It.IsAny<RequestHeader>(),
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It.Is<bool>(release => release),
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It.IsAny<ByteStringCollection>(),
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It.IsAny<CancellationToken>()))
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.ReturnsAsync(releaseResp);
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return mock;
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}
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/// <summary>
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/// When the caller's <see cref="CancellationToken"/> fires mid-pagination,
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/// <c>DiscoverAsync</c> must call <c>BrowseNextAsync(releaseContinuationPoints: true)</c>
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/// before the exception propagates, so the server-side cursor is freed rather than
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/// held open until session close.
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/// </summary>
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[Fact]
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public async Task DiscoverAsync_releases_continuation_point_when_cancelled_mid_pagination()
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{
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var ct = TestContext.Current.CancellationToken;
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using var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions(), "opcua-cp-release");
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var sessionMock = BuildCancellingSessionMock();
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drv.SetSessionForTest(sessionMock.Object);
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var builder = new NullAddressSpaceBuilder();
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// DiscoverAsync should throw (OperationCanceledException propagates after release),
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// but the release BrowseNextAsync(release=true) must be called first.
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await Should.ThrowAsync<OperationCanceledException>(async () =>
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await drv.DiscoverAsync(builder, ct));
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// Verify the release call was made exactly once with releaseContinuationPoints=true.
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sessionMock.Verify(s => s.BrowseNextAsync(
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It.IsAny<RequestHeader>(),
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It.Is<bool>(release => release),
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It.IsAny<ByteStringCollection>(),
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It.IsAny<CancellationToken>()),
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Times.Once,
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"DiscoverAsync must release the server-side continuation point on cancellation " +
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"(Driver.OpcUaClient-016 / Browser-002 cross-module finding)");
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}
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/// <summary>
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/// Transient browse failure (non-cancellation exception) must NOT attempt a release —
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/// the server already cleaned up (the request never reached the page-fetch state), and
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/// calling BrowseNext on a bad continuation point would add noise to the server log.
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/// <c>BrowseRecursiveAsync</c>'s existing catch swallows transient failures silently;
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/// we should not change that behaviour.
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/// </summary>
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[Fact]
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public async Task DiscoverAsync_does_not_release_continuation_point_on_non_cancel_browse_failure()
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{
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var ct = TestContext.Current.CancellationToken;
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using var drv = new OpcUaClientDriver(new OpcUaClientDriverOptions(), "opcua-cp-norelease");
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var mock = new Mock<ISession>(MockBehavior.Loose);
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mock.SetupGet(s => s.MessageContext).Returns(new ServiceMessageContext());
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mock.SetupGet(s => s.NamespaceUris).Returns(new NamespaceTable());
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// BrowseAsync — return a result with a continuation point so the loop is entered.
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var firstRef = new ReferenceDescription
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{
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NodeId = new ExpandedNodeId(new NodeId(1001, 2), "opc.tcp://test"),
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BrowseName = new QualifiedName("TestObj2", 2),
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DisplayName = new LocalizedText("TestObj2"),
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NodeClass = NodeClass.Object,
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};
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var browseResult = new BrowseResult
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{
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ContinuationPoint = FakeContinuationPoint,
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References = new ReferenceDescriptionCollection { firstRef },
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};
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mock.Setup(s => s.BrowseAsync(
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It.IsAny<RequestHeader>(),
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It.IsAny<ViewDescription>(),
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It.IsAny<uint>(),
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It.IsAny<BrowseDescriptionCollection>(),
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It.IsAny<CancellationToken>()))
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.ReturnsAsync(new BrowseResponse
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{
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ResponseHeader = new ResponseHeader(),
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Results = new BrowseResultCollection { browseResult },
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DiagnosticInfos = new DiagnosticInfoCollection(),
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});
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// BrowseNextAsync — throw a non-cancellation transport error.
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mock.Setup(s => s.BrowseNextAsync(
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It.IsAny<RequestHeader>(),
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It.Is<bool>(release => !release),
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It.IsAny<ByteStringCollection>(),
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It.IsAny<CancellationToken>()))
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.ThrowsAsync(new ServiceResultException(StatusCodes.BadCommunicationError));
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drv.SetSessionForTest(mock.Object);
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// DiscoverAsync catches the transient failure and continues (returns normally since
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// the root sub-tree failure just skips that branch).
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await drv.DiscoverAsync(new NullAddressSpaceBuilder(), ct);
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// The release call must NOT be made for a transport error — only for cancellation.
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mock.Verify(s => s.BrowseNextAsync(
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It.IsAny<RequestHeader>(),
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It.Is<bool>(release => release),
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It.IsAny<ByteStringCollection>(),
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It.IsAny<CancellationToken>()),
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Times.Never,
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"A transient transport failure must not trigger a release BrowseNext call");
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}
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/// <summary>Minimal no-op address space builder for discovery tests.</summary>
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private sealed class NullAddressSpaceBuilder : IAddressSpaceBuilder
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{
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/// <inheritdoc />
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public IAddressSpaceBuilder Folder(string browseName, string displayName) => this;
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/// <inheritdoc />
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public IVariableHandle Variable(string browseName, string displayName, DriverAttributeInfo attributeInfo)
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=> new StubHandle();
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/// <inheritdoc />
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public void AddProperty(string browseName, DriverDataType dataType, object? value) { }
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/// <inheritdoc />
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public void AttachAlarmCondition(IVariableHandle sourceVariable, string alarmName, DriverAttributeInfo alarmInfo) { }
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private sealed class StubHandle : IVariableHandle
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{
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public string FullReference => "stub";
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public IAlarmConditionSink MarkAsAlarmCondition(AlarmConditionInfo info) => throw new NotSupportedException();
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}
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}
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}
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