Various improvements.

Rename type to 'Context'; this matches the existing UsePeriodicPasswordProvider.
Add CancellationToken; the user might execute commands against the server that might need to be cancelled.
Remove sync overload; it could be unnecessary.
Move types to their own files.
Allow multiple callbacks to be added.

Signed-off-by: Bradley Grainger <[email protected]>

src/MySqlConnector/MySqlConnection.cs

@@ -584,7 +584,10 @@ internal async Task OpenAsync(IOBehavior? ioBehavior, CancellationToken cancella
 				EnlistTransaction(System.Transactions.Transaction.Current);
 
 			if (ConnectionOpenedCallback is { } connectionOpenedCallback)
-				await connectionOpenedCallback(new(this, m_session.Conditions)).ConfigureAwait(false);
+			{
+				cancellationToken.ThrowIfCancellationRequested();
+				await connectionOpenedCallback(new(this, m_session.Conditions), cancellationToken).ConfigureAwait(false);
+			}
 		}
 		catch (Exception ex) when (activity is { IsAllDataRequested: true })
 		{

src/MySqlConnector/MySqlConnectionOpenedCallback.cs

@@ -3,47 +3,7 @@ namespace MySqlConnector;
 /// <summary>
 /// A callback that is invoked when a new <see cref="MySqlConnection"/> is opened.
 /// </summary>
-/// <param name="data">A <see cref="MySqlConnectionOpenedData"/> giving information about the connection being opened.</param>
+/// <param name="context">A <see cref="MySqlConnectionOpenedContext"/> giving information about the connection being opened.</param>
+/// <param name="cancellationToken">A <see cref="CancellationToken"/> that can be used to cancel the asynchronous operation.</param>
 /// <returns>A <see cref="ValueTask"/> representing the result of the possibly-asynchronous operation.</returns>
-public delegate ValueTask MySqlConnectionOpenedCallback(MySqlConnectionOpenedData data);
-
-public sealed class MySqlConnectionOpenedData
-{
-	/// <summary>
-	/// The <see cref="MySqlConnection"/> that was opened.
-	/// </summary>
-	public MySqlConnection Connection { get; }
-
-	/// <summary>
-	/// Bitflags giving the conditions under which a connection was opened.
-	/// </summary>
-	public MySqlConnectionOpenedConditions Conditions { get; }
-
-	internal MySqlConnectionOpenedData(MySqlConnection connection, MySqlConnectionOpenedConditions conditions)
-	{
-		Connection = connection;
-		Conditions = conditions;
-	}
-}
-
-/// <summary>
-/// Bitflags giving the conditions under which a connection was opened.
-/// </summary>
-[Flags]
-public enum MySqlConnectionOpenedConditions
-{
-	/// <summary>
-	/// No specific conditions apply. This value may be used when an existing pooled connection is reused without being reset.
-	/// </summary>
-	None = 0,
-
-	/// <summary>
-	/// A new physical connection to a MySQL Server was opened. This value is mutually exclusive with <see cref="Reset"/>.
-	/// </summary>
-	New = 1,
-
-	/// <summary>
-	/// An existing pooled connection to a MySQL Server was reset. This value is mutually exclusive with <see cref="New"/>.
-	/// </summary>
-	Reset = 2,
-}
+public delegate ValueTask MySqlConnectionOpenedCallback(MySqlConnectionOpenedContext context, CancellationToken cancellationToken);

src/MySqlConnector/MySqlConnectionOpenedConditions.cs

@@ -0,0 +1,23 @@
+namespace MySqlConnector;
+
+/// <summary>
+/// Bitflags giving the conditions under which a connection was opened.
+/// </summary>
+[Flags]
+public enum MySqlConnectionOpenedConditions
+{
+	/// <summary>
+	/// No specific conditions apply. This value may be used when an existing pooled connection is reused without being reset.
+	/// </summary>
+	None = 0,
+
+	/// <summary>
+	/// A new physical connection to a MySQL Server was opened. This value is mutually exclusive with <see cref="Reset"/>.
+	/// </summary>
+	New = 1,
+
+	/// <summary>
+	/// An existing pooled connection to a MySQL Server was reset. This value is mutually exclusive with <see cref="New"/>.
+	/// </summary>
+	Reset = 2,
+}

src/MySqlConnector/MySqlConnectionOpenedContext.cs

@@ -0,0 +1,23 @@
+namespace MySqlConnector;
+
+/// <summary>
+/// Contains information passed to <see cref="MySqlConnectionOpenedCallback"/> when a new <see cref="MySqlConnection"/> is opened.
+/// </summary>
+public sealed class MySqlConnectionOpenedContext
+{
+	/// <summary>
+	/// The <see cref="MySqlConnection"/> that was opened.
+	/// </summary>
+	public MySqlConnection Connection { get; }
+
+	/// <summary>
+	/// Bitflags giving the conditions under which a connection was opened.
+	/// </summary>
+	public MySqlConnectionOpenedConditions Conditions { get; }
+
+	internal MySqlConnectionOpenedContext(MySqlConnection connection, MySqlConnectionOpenedConditions conditions)
+	{
+		Connection = connection;
+		Conditions = conditions;
+	}
+}

src/MySqlConnector/MySqlDataSourceBuilder.cs

@@ -89,19 +89,14 @@ public MySqlDataSourceBuilder UseRemoteCertificateValidationCallback(RemoteCerti
 		return this;
 	}
 
+	/// <summary>
+	/// Adds a callback that is invoked when a new <see cref="MySqlConnection"/> is opened.
+	/// </summary>
+	/// <param name="callback">The callback to invoke.</param>
+	/// <returns>This builder, so that method calls can be chained.</returns>
 	public MySqlDataSourceBuilder UseConnectionOpenedCallback(MySqlConnectionOpenedCallback callback)
 	{
-		m_connectionOpenedCallback = callback;
-		return this;
-	}
-
-	public MySqlDataSourceBuilder UseConnectionOpenedCallback(Action<MySqlConnectionOpenedData> callback)
-	{
-		m_connectionOpenedCallback = data =>
-		{
-			callback(data);
-			return default;
-		};
+		m_connectionOpenedCallback += callback;
 		return this;
 	}
 

tests/MySqlConnector.Tests/ConnectionOpenedCallbackTests.cs

@@ -44,28 +44,6 @@ public void CallbackIsInvoked()
 		}
 	}
 
-	[Fact]
-	public void SyncCallbackIsInvoked()
-	{
-		var dataSource = new MySqlDataSourceBuilder(m_csb.ConnectionString)
-			.UseConnectionOpenedCallback(data =>
-			{
-				m_connectionOpenedCount++;
-				m_connectionOpenedConditions = data.Conditions;
-			})
-			.Build();
-		using (var connection = dataSource.CreateConnection())
-		{
-			Assert.Equal(0, m_connectionOpenedCount);
-			Assert.Equal(MySqlConnectionOpenedConditions.None, m_connectionOpenedConditions);
-
-			connection.Open();
-
-			Assert.Equal(1, m_connectionOpenedCount);
-			Assert.Equal(MySqlConnectionOpenedConditions.New, m_connectionOpenedConditions);
-		}
-	}
-
 	[Fact]
 	public void CallbackIsInvokedForPooledConnection()
 	{
@@ -146,7 +124,7 @@ public void ConditionsForNonResetConnection()
 		}
 	}
 
-	private ValueTask OnConnectionOpenedAsync(MySqlConnectionOpenedData data)
+	private ValueTask OnConnectionOpenedAsync(MySqlConnectionOpenedContext data, CancellationToken cancellationToken)
 	{
 		m_connectionOpenedCount++;
 		m_connectionOpenedConditions = data.Conditions;