fix: honour Spanner emulator detection in outbox/inbox connections (#4162)

.gitignore

@@ -350,3 +350,6 @@ ralph.log
 
 # AI agent session state
 PROMPT.md
+
+# Local-only docker compose overrides (e.g. port remaps for host conflicts)
+docker-compose-*.local.yaml

bugfixes/.current-bug

@@ -1 +1 @@
-0003-pump-span-leak-exception-paths
+0004-spanner-emulator-detection

bugfixes/0004-spanner-emulator-detection/.issue-number

@@ -0,0 +1 @@
+4162

src/Paramore.Brighter.Spanner/SpannerConnectionProvider.cs

@@ -1,6 +1,7 @@
 using System.Data.Common;
 using System.Threading;
 using System.Threading.Tasks;
+using Google.Api.Gax;
 using Google.Cloud.Spanner.Data;
 
 namespace Paramore.Brighter.Spanner;
@@ -14,7 +15,13 @@ namespace Paramore.Brighter.Spanner;
 public class SpannerConnectionProvider(IAmARelationalDatabaseConfiguration configuration)
     : RelationalDbConnectionProvider
 {
-    private readonly string _connectionString = configuration.ConnectionString;
+    // Enable emulator detection so the connection routes to SPANNER_EMULATOR_HOST when it is set,
+    // and behaves as normal production otherwise. The keyword serialises into the connection string.
+    private readonly string _connectionString =
+        new SpannerConnectionStringBuilder(configuration.ConnectionString)
+        {
+            EmulatorDetection = EmulatorDetection.EmulatorOrProduction
+        }.ConnectionString;
 
     /// <inheritdoc />
     public override DbConnection GetConnection()

src/Paramore.Brighter.Spanner/SpannerUnitOfWork.cs

@@ -2,6 +2,7 @@
 using System.Data.Common;
 using System.Threading;
 using System.Threading.Tasks;
+using Google.Api.Gax;
 using Google.Cloud.Spanner.Data;
 
 namespace Paramore.Brighter.Spanner;
@@ -20,8 +21,14 @@ namespace Paramore.Brighter.Spanner;
 /// <param name="configuration">The configuration containing the connection string for the Spanner database.</param>
 public class SpannerUnitOfWork(IAmARelationalDatabaseConfiguration configuration) : RelationalDbTransactionProvider
 {
-    private readonly string _connectionString = configuration.ConnectionString;
-
+    // Enable emulator detection so the connection routes to SPANNER_EMULATOR_HOST when it is set,
+    // and behaves as normal production otherwise. The keyword serialises into the connection string.
+    private readonly string _connectionString =
+        new SpannerConnectionStringBuilder(configuration.ConnectionString)
+        {
+            EmulatorDetection = EmulatorDetection.EmulatorOrProduction
+        }.ConnectionString;
+
     /// <inheritdoc />
     public override DbConnection GetConnection()
     {

tests/Paramore.Brighter.Gcp.Tests/Spanner/Connection/When_a_spanner_connection_provider_opens_a_connection_it_should_honour_the_spanner_emulator.cs

@@ -0,0 +1,36 @@
+using System.Data;
+using System.Threading.Tasks;
+using Google.Cloud.Spanner.Data;
+using Paramore.Brighter.Gcp.Tests.Helper;
+using Paramore.Brighter.Spanner;
+using Xunit;
+
+namespace Paramore.Brighter.Gcp.Tests.Spanner.Connection;
+
+[Trait("Category", "Spanner")]
+public class SpannerConnectionProviderEmulatorTests
+{
+    // A bare connection string with no EmulatorDetection keyword — the shape production code
+    // receives via RelationalDatabaseConfiguration. Built inline (not via Const) so this test
+    // stays scoped to the provider's own emulator handling even after Const is patched.
+    private readonly string _bareConnectionString =
+        $"Data Source=projects/{GatewayFactory.GetProjectId()}/instances/brighter-spanner/databases/brightertests";
+
+    [Fact]
+    public async Task When_a_spanner_connection_provider_opens_a_connection_it_should_honour_the_spanner_emulator()
+    {
+        // Arrange
+        var configuration = new RelationalDatabaseConfiguration(_bareConnectionString);
+        var provider = new SpannerConnectionProvider(configuration);
+
+        // Act
+        await using var connection = await provider.GetConnectionAsync();
+
+        using var command = ((SpannerConnection)connection).CreateSelectCommand("SELECT 1");
+        var result = (long)(await command.ExecuteScalarAsync())!;
+
+        // Assert
+        Assert.Equal(ConnectionState.Open, connection.State);
+        Assert.Equal(1L, result);
+    }
+}

tests/Paramore.Brighter.Gcp.Tests/Spanner/Const.cs

@@ -1,9 +1,19 @@
-using Paramore.Brighter.Gcp.Tests.Helper;
+using Google.Api.Gax;
+using Google.Cloud.Spanner.Data;
+using Paramore.Brighter.Gcp.Tests.Helper;
 
 namespace Paramore.Brighter.Gcp.Tests.Spanner;
 
 public static class Const
 {
-    public static string ConnectionString => $"Data Source=projects/{GatewayFactory.GetProjectId()}/instances/brighter-spanner/databases/brightertests";
+    // Embed EmulatorDetection into the connection string so it round-trips through
+    // RelationalDatabaseConfiguration into the tests' own DDL connections and the outbox/inbox's
+    // internal connections, routing to SPANNER_EMULATOR_HOST when set instead of demanding ADC.
+    public static string ConnectionString => new SpannerConnectionStringBuilder(
+        $"Data Source=projects/{GatewayFactory.GetProjectId()}/instances/brighter-spanner/databases/brightertests")
+    {
+        EmulatorDetection = EmulatorDetection.EmulatorOrProduction
+    }.ConnectionString;
+
     public const string TablePrefix = "test_";
 }