feat(otopcua): add ITagDiscovery.RediscoverPolicy + per-driver assignments (follow-up B)

src/Core/ZB.MOM.WW.OtOpcUa.Core.Abstractions/ITagDiscovery.cs

@@ -1,5 +1,17 @@
 namespace ZB.MOM.WW.OtOpcUa.Core.Abstractions;
 
+/// <summary>How aggressively the host re-runs post-connect discovery for this driver.</summary>
+public enum DiscoveryRediscoverPolicy
+{
+    /// <summary>Retry every interval up to the cap or until the captured set is non-empty and stable
+    /// (for drivers whose discovered shape fills in asynchronously after connect, e.g. the FOCAS FixedTree).</summary>
+    UntilStable,
+    /// <summary>Run exactly one discovery pass on connect (drivers that discover synchronously in DiscoverAsync).</summary>
+    Once,
+    /// <summary>Never run post-connect discovery.</summary>
+    Never,
+}
+
 /// <summary>
 ///     Driver capability for discovering tags and hierarchy from the backend.
 ///     Streams discovered nodes into <see cref="IAddressSpaceBuilder"/> rather than
@@ -14,4 +26,7 @@ public interface ITagDiscovery
     /// <param name="builder">The address space builder to stream discovered nodes into.</param>
     /// <param name="cancellationToken">A cancellation token for the discovery operation.</param>
     Task DiscoverAsync(IAddressSpaceBuilder builder, CancellationToken cancellationToken);
+
+    /// <summary>Post-connect re-discovery policy. Default preserves the original retry-until-stable behavior.</summary>
+    DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.UntilStable;
 }

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipDriver.cs

@@ -998,6 +998,14 @@ public sealed class AbCipDriver : IDriver, IReadable, IWritable, ITagDiscovery,
 
     // ---- ITagDiscovery ----
 
+    /// <summary>
+    ///     Run-once: <see cref="DiscoverAsync"/> emits pre-declared tags and (when
+    ///     EnableControllerBrowse is set) fully awaits the @tags symbol-table walk + UDT-shape
+    ///     resolution within the single call, streaming the complete node set in one pass —
+    ///     nothing fills in asynchronously after connect, so a single discovery pass is sufficient.
+    /// </summary>
+    public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.Once;
+
     /// <summary>
     ///     Stream the driver's tag set into the builder. Pre-declared tags from
     ///     <see cref="AbCipDriverOptions.Tags"/> emit first; optionally, the

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy/AbLegacyDriver.cs

@@ -422,6 +422,13 @@ public sealed class AbLegacyDriver : IDriver, IReadable, IWritable, ITagDiscover
 
     // ---- ITagDiscovery ----
 
+    /// <summary>
+    ///     Run-once: <see cref="DiscoverAsync"/> emits the complete node set synchronously from
+    ///     the configured device/tag tables within a single pass — there is no shape that fills
+    ///     in asynchronously after connect, so a single discovery pass is sufficient.
+    /// </summary>
+    public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.Once;
+
     /// <summary>
     ///     Discovers tags and populates the address space asynchronously.
     /// </summary>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS/FocasDriver.cs

@@ -401,6 +401,14 @@ public sealed class FocasDriver : IDriver, IReadable, IWritable, ITagDiscovery,
 
     // ---- ITagDiscovery ----
 
+    /// <summary>
+    ///     Retry-until-stable: the FixedTree subtree is filled in asynchronously by
+    ///     <see cref="FixedTreeLoopAsync"/> a couple of seconds AFTER connect, so the first
+    ///     post-connect <see cref="DiscoverAsync"/> pass would miss it — the host must re-run
+    ///     discovery until the captured node set is non-empty and stable.
+    /// </summary>
+    public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.UntilStable;
+
     /// <summary>Discovers tags and builds the OPC UA address space asynchronously.</summary>
     /// <param name="builder">The address space builder for constructing the OPC UA namespace.</param>
     /// <param name="cancellationToken">Cancellation token for the operation.</param>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.OpcUaClient/OpcUaClientDriver.cs

@@ -826,6 +826,14 @@ public sealed class OpcUaClientDriver : IDriver, ITagDiscovery, IReadable, IWrit
 
     // ---- ITagDiscovery ----
 
+    /// <summary>
+    ///     Run-once: <see cref="DiscoverAsync"/> recursively browses the remote server's address
+    ///     space and registers every variable within the single call (browse + enrich passes are
+    ///     fully awaited) — nothing fills in asynchronously after connect, so a single discovery
+    ///     pass is sufficient.
+    /// </summary>
+    public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.Once;
+
     /// <summary>Discovers the remote OPC UA server's address space and materializes it through the supplied builder.</summary>
     /// <param name="builder">Address space builder for materializing discovered nodes.</param>
     /// <param name="cancellationToken">Cancellation token for the operation.</param>

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.TwinCAT/TwinCATDriver.cs

@@ -377,6 +377,14 @@ public sealed class TwinCATDriver : IDriver, IReadable, IWritable, ITagDiscovery
 
     // ---- ITagDiscovery ----
 
+    /// <summary>
+    ///     Run-once: <see cref="DiscoverAsync"/> emits pre-declared tags and (when
+    ///     EnableControllerBrowse is set) fully awaits the controller symbol browse within the
+    ///     single call, streaming the complete node set in one pass — nothing fills in
+    ///     asynchronously after connect, so a single discovery pass is sufficient.
+    /// </summary>
+    public DiscoveryRediscoverPolicy RediscoverPolicy => DiscoveryRediscoverPolicy.Once;
+
     /// <summary>Discovers devices and tags from ADS configuration and optionally controller symbols.</summary>
     /// <param name="builder">Address space builder for adding discovered nodes.</param>
     /// <param name="cancellationToken">Cancellation token.</param>

tests/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Tests/FocasScaffoldingTests.cs

@@ -203,6 +203,18 @@ public sealed class FocasScaffoldingTests
         drv.DriverInstanceId.ShouldBe("drv-1");
     }
 
+    /// <summary>
+    ///     Verifies FOCAS opts into retry-until-stable post-connect re-discovery — its
+    ///     FixedTree subtree is populated asynchronously by a background loop a couple of
+    ///     seconds after connect, so a single DiscoverAsync pass would miss it.
+    /// </summary>
+    [Fact]
+    public void RediscoverPolicy_is_UntilStable()
+    {
+        var drv = new FocasDriver(new FocasDriverOptions(), "drv-1");
+        drv.RediscoverPolicy.ShouldBe(DiscoveryRediscoverPolicy.UntilStable);
+    }
+
     /// <summary>Verifies InitializeAsync parses device addresses correctly.</summary>
     [Fact]
     public async Task InitializeAsync_parses_device_addresses()