[Do not merge] Update nullable annotations for header dictionary value types

src/NServiceBus.Core.Tests/ApprovalFiles/APIApprovals.ApproveNServiceBus.approved.txt

@@ -139,8 +139,8 @@ namespace NServiceBus
     }
     public class ConversationIdStrategyContext
     {
-        public ConversationIdStrategyContext(NServiceBus.Pipeline.OutgoingLogicalMessage message, System.Collections.Generic.IReadOnlyDictionary<string, string> headers) { }
-        public System.Collections.Generic.IReadOnlyDictionary<string, string> Headers { get; }
+        public ConversationIdStrategyContext(NServiceBus.Pipeline.OutgoingLogicalMessage message, System.Collections.Generic.IReadOnlyDictionary<string, string?> headers) { }
+        public System.Collections.Generic.IReadOnlyDictionary<string, string?> Headers { get; }
         public NServiceBus.Pipeline.OutgoingLogicalMessage Message { get; }
     }
     public static class ConversationRoutingExtensions
@@ -358,8 +358,8 @@ namespace NServiceBus
     }
     public static class HeaderOptionExtensions
     {
-        public static System.Collections.Generic.IReadOnlyDictionary<string, string> GetHeaders(this NServiceBus.Extensibility.ExtendableOptions options) { }
-        public static void SetHeader(this NServiceBus.Extensibility.ExtendableOptions options, string key, string value) { }
+        public static System.Collections.Generic.IReadOnlyDictionary<string, string?> GetHeaders(this NServiceBus.Extensibility.ExtendableOptions options) { }
+        public static void SetHeader(this NServiceBus.Extensibility.ExtendableOptions options, string key, string? value) { }
     }
     public static class Headers
     {
@@ -1761,19 +1761,19 @@ namespace NServiceBus.MessageMutator
     }
     public class MutateOutgoingMessageContext : NServiceBus.ICancellableContext
     {
-        public MutateOutgoingMessageContext(object outgoingMessage, System.Collections.Generic.Dictionary<string, string> outgoingHeaders, object? incomingMessage, System.Collections.Generic.IReadOnlyDictionary<string, string>? incomingHeaders, System.Threading.CancellationToken cancellationToken = default) { }
+        public MutateOutgoingMessageContext(object outgoingMessage, System.Collections.Generic.Dictionary<string, string?> outgoingHeaders, object? incomingMessage, System.Collections.Generic.IReadOnlyDictionary<string, string>? incomingHeaders, System.Threading.CancellationToken cancellationToken = default) { }
         public System.Threading.CancellationToken CancellationToken { get; }
-        public System.Collections.Generic.Dictionary<string, string> OutgoingHeaders { get; }
+        public System.Collections.Generic.Dictionary<string, string?> OutgoingHeaders { get; }
         public object OutgoingMessage { get; set; }
         public bool TryGetIncomingHeaders([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] out System.Collections.Generic.IReadOnlyDictionary<string, string>? incomingHeaders) { }
         public bool TryGetIncomingMessage([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] out object? incomingMessage) { }
     }
     public class MutateOutgoingTransportMessageContext : NServiceBus.ICancellableContext
     {
-        public MutateOutgoingTransportMessageContext(System.ReadOnlyMemory<byte> outgoingBody, object outgoingMessage, System.Collections.Generic.Dictionary<string, string> outgoingHeaders, object? incomingMessage, System.Collections.Generic.IReadOnlyDictionary<string, string>? incomingHeaders, System.Threading.CancellationToken cancellationToken = default) { }
+        public MutateOutgoingTransportMessageContext(System.ReadOnlyMemory<byte> outgoingBody, object outgoingMessage, System.Collections.Generic.Dictionary<string, string?> outgoingHeaders, object? incomingMessage, System.Collections.Generic.IReadOnlyDictionary<string, string>? incomingHeaders, System.Threading.CancellationToken cancellationToken = default) { }
         public System.Threading.CancellationToken CancellationToken { get; }
         public System.ReadOnlyMemory<byte> OutgoingBody { get; set; }
-        public System.Collections.Generic.Dictionary<string, string> OutgoingHeaders { get; }
+        public System.Collections.Generic.Dictionary<string, string?> OutgoingHeaders { get; }
         public object OutgoingMessage { get; }
         public bool TryGetIncomingHeaders([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] out System.Collections.Generic.IReadOnlyDictionary<string, string>? incomingHeaders) { }
         public bool TryGetIncomingMessage([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] out object? incomingMessage) { }
@@ -1931,7 +1931,7 @@ namespace NServiceBus.Pipeline
     }
     public interface IOutgoingContext : NServiceBus.Extensibility.IExtendable, NServiceBus.ICancellableContext, NServiceBus.IPipelineContext, NServiceBus.Pipeline.IBehaviorContext
     {
-        System.Collections.Generic.Dictionary<string, string> Headers { get; }
+        System.Collections.Generic.Dictionary<string, string?> Headers { get; }
         string MessageId { get; }
     }
     public interface IOutgoingLogicalMessageContext : NServiceBus.Extensibility.IExtendable, NServiceBus.ICancellableContext, NServiceBus.IPipelineContext, NServiceBus.Pipeline.IBehaviorContext, NServiceBus.Pipeline.IOutgoingContext

src/NServiceBus.Core/Causation/ConversationIdStrategyContext.cs

@@ -14,7 +14,7 @@ public class ConversationIdStrategyContext
     /// <summary>
     /// Creates a new context.
     /// </summary>
-    public ConversationIdStrategyContext(OutgoingLogicalMessage message, IReadOnlyDictionary<string, string> headers)
+    public ConversationIdStrategyContext(OutgoingLogicalMessage message, IReadOnlyDictionary<string, string?> headers)
     {
         ArgumentNullException.ThrowIfNull(message);
         ArgumentNullException.ThrowIfNull(headers);
@@ -32,5 +32,5 @@ public ConversationIdStrategyContext(OutgoingLogicalMessage message, IReadOnlyDi
     /// <summary>
     /// The headers attached to the outgoing message.
     /// </summary>
-    public IReadOnlyDictionary<string, string> Headers { get; }
+    public IReadOnlyDictionary<string, string?> Headers { get; }
 }

src/NServiceBus.Core/Extensibility/ExtendableOptions.cs

@@ -30,5 +30,5 @@ protected ExtendableOptions()
 
     internal string? UserDefinedMessageId { get; set; }
 
-    internal Dictionary<string, string> OutgoingHeaders { get; }
+    internal Dictionary<string, string?> OutgoingHeaders { get; }
 }

src/NServiceBus.Core/MessageMutators/MutateInstanceMessage/MutateOutgoingMessageContext.cs

@@ -15,7 +15,7 @@ public class MutateOutgoingMessageContext : ICancellableContext
     /// <summary>
     /// Initializes the context.
     /// </summary>
-    public MutateOutgoingMessageContext(object outgoingMessage, Dictionary<string, string> outgoingHeaders, object? incomingMessage, IReadOnlyDictionary<string, string>? incomingHeaders, CancellationToken cancellationToken = default)
+    public MutateOutgoingMessageContext(object outgoingMessage, Dictionary<string, string?> outgoingHeaders, object? incomingMessage, IReadOnlyDictionary<string, string>? incomingHeaders, CancellationToken cancellationToken = default)
     {
         ArgumentNullException.ThrowIfNull(outgoingHeaders);
         ArgumentNullException.ThrowIfNull(outgoingMessage);
@@ -43,7 +43,7 @@ public object OutgoingMessage
     /// <summary>
     /// The current outgoing headers.
     /// </summary>
-    public Dictionary<string, string> OutgoingHeaders { get; }
+    public Dictionary<string, string?> OutgoingHeaders { get; }
 
     /// <summary>
     /// A <see cref="CancellationToken"/> to observe.

src/NServiceBus.Core/MessageMutators/MutateTransportMessage/MutateOutgoingTransportMessageContext.cs

@@ -15,7 +15,7 @@ public class MutateOutgoingTransportMessageContext : ICancellableContext
     /// <summary>
     /// Initializes a new instance of <see cref="MutateOutgoingTransportMessageContext" />.
     /// </summary>
-    public MutateOutgoingTransportMessageContext(ReadOnlyMemory<byte> outgoingBody, object outgoingMessage, Dictionary<string, string> outgoingHeaders, object? incomingMessage, IReadOnlyDictionary<string, string>? incomingHeaders, CancellationToken cancellationToken = default)
+    public MutateOutgoingTransportMessageContext(ReadOnlyMemory<byte> outgoingBody, object outgoingMessage, Dictionary<string, string?> outgoingHeaders, object? incomingMessage, IReadOnlyDictionary<string, string>? incomingHeaders, CancellationToken cancellationToken = default)
     {
         ArgumentNullException.ThrowIfNull(outgoingHeaders);
         ArgumentNullException.ThrowIfNull(outgoingMessage);
@@ -51,7 +51,7 @@ public ReadOnlyMemory<byte> OutgoingBody
     /// <summary>
     /// The current outgoing headers.
     /// </summary>
-    public Dictionary<string, string> OutgoingHeaders { get; }
+    public Dictionary<string, string?> OutgoingHeaders { get; }
 
     /// <summary>
     /// A <see cref="CancellationToken"/> to observe.

src/NServiceBus.Core/Pipeline/Outgoing/HeaderOptionExtensions.cs

@@ -18,7 +18,7 @@ public static class HeaderOptionExtensions
     /// <param name="options">The options to extend.</param>
     /// <param name="key">The header key.</param>
     /// <param name="value">The header value.</param>
-    public static void SetHeader(this ExtendableOptions options, string key, string value)
+    public static void SetHeader(this ExtendableOptions options, string key, string? value)
     {
         ArgumentNullException.ThrowIfNull(options);
         ArgumentException.ThrowIfNullOrWhiteSpace(key);
@@ -29,10 +29,10 @@ public static void SetHeader(this ExtendableOptions options, string key, string
     /// <summary>
     /// Returns all headers set by <see cref="SetHeader" /> on the outgoing message.
     /// </summary>
-    public static IReadOnlyDictionary<string, string> GetHeaders(this ExtendableOptions options)
+    public static IReadOnlyDictionary<string, string?> GetHeaders(this ExtendableOptions options)
     {
         ArgumentNullException.ThrowIfNull(options);
 
-        return new ReadOnlyDictionary<string, string>(options.OutgoingHeaders);
+        return new ReadOnlyDictionary<string, string?>(options.OutgoingHeaders);
     }
 }

src/NServiceBus.Core/Pipeline/Outgoing/IOutgoingContext.cs

@@ -17,5 +17,5 @@ public interface IOutgoingContext : IBehaviorContext, IPipelineContext
     /// <summary>
     /// The headers of the outgoing message.
     /// </summary>
-    Dictionary<string, string> Headers { get; }
+    Dictionary<string, string?> Headers { get; }
 }

src/NServiceBus.Core/Pipeline/Outgoing/OutgoingContext.cs

@@ -10,7 +10,7 @@ namespace NServiceBus;
 
 abstract class OutgoingContext : BehaviorContext, IOutgoingContext
 {
-    protected OutgoingContext(string messageId, Dictionary<string, string> headers, IBehaviorContext parentContext)
+    protected OutgoingContext(string messageId, Dictionary<string, string?> headers, IBehaviorContext parentContext)
         : base(parentContext)
     {
         Headers = headers;
@@ -21,7 +21,7 @@ protected OutgoingContext(string messageId, Dictionary<string, string> headers,
 
     public string MessageId { get; }
 
-    public Dictionary<string, string> Headers { get; }
+    public Dictionary<string, string?> Headers { get; }
 
     public Task Send(object message, SendOptions options)
     {

src/NServiceBus.Core/Pipeline/Outgoing/OutgoingLogicalMessageContext.cs

@@ -9,7 +9,7 @@ namespace NServiceBus;
 
 class OutgoingLogicalMessageContext : OutgoingContext, IOutgoingLogicalMessageContext
 {
-    public OutgoingLogicalMessageContext(string messageId, Dictionary<string, string> headers, OutgoingLogicalMessage message, IReadOnlyCollection<RoutingStrategy> routingStrategies, IBehaviorContext parentContext)
+    public OutgoingLogicalMessageContext(string messageId, Dictionary<string, string?> headers, OutgoingLogicalMessage message, IReadOnlyCollection<RoutingStrategy> routingStrategies, IBehaviorContext parentContext)
         : base(messageId, headers, parentContext)
     {
         Message = message;

src/NServiceBus.Core/Pipeline/Outgoing/OutgoingPublishContext.cs

@@ -9,7 +9,7 @@ namespace NServiceBus;
 
 class OutgoingPublishContext : OutgoingContext, IOutgoingPublishContext
 {
-    public OutgoingPublishContext(OutgoingLogicalMessage message, string messageId, Dictionary<string, string> headers, ContextBag extensions, IBehaviorContext parentContext)
+    public OutgoingPublishContext(OutgoingLogicalMessage message, string messageId, Dictionary<string, string?> headers, ContextBag extensions, IBehaviorContext parentContext)
         : base(messageId, headers, parentContext)
     {
         ArgumentNullException.ThrowIfNull(parentContext);

src/NServiceBus.Core/Pipeline/Outgoing/OutgoingReplyContext.cs

@@ -9,7 +9,7 @@ namespace NServiceBus;
 
 class OutgoingReplyContext : OutgoingContext, IOutgoingReplyContext
 {
-    public OutgoingReplyContext(OutgoingLogicalMessage message, string messageId, Dictionary<string, string> headers, ContextBag extensions, IBehaviorContext parentContext)
+    public OutgoingReplyContext(OutgoingLogicalMessage message, string messageId, Dictionary<string, string?> headers, ContextBag extensions, IBehaviorContext parentContext)
         : base(messageId, headers, parentContext)
     {
         ArgumentNullException.ThrowIfNull(parentContext);

src/NServiceBus.Core/Pipeline/Outgoing/OutgoingSendContext.cs

@@ -9,7 +9,7 @@ namespace NServiceBus;
 
 class OutgoingSendContext : OutgoingContext, IOutgoingSendContext
 {
-    public OutgoingSendContext(OutgoingLogicalMessage message, string messageId, Dictionary<string, string> headers, ContextBag extensions, IBehaviorContext parentContext)
+    public OutgoingSendContext(OutgoingLogicalMessage message, string messageId, Dictionary<string, string?> headers, ContextBag extensions, IBehaviorContext parentContext)
         : base(messageId, headers, parentContext)
     {
         ArgumentNullException.ThrowIfNull(parentContext);

src/NServiceBus.Core/Unicast/MessageOperations.cs

@@ -1,3 +1,5 @@
+#nullable enable
+
 namespace NServiceBus;
 
 using System;
@@ -39,20 +41,20 @@ public MessageOperations(
 
     public Task Publish<[DynamicallyAccessedMembers(IMessageCreator.CreatorMembersRequired)] T>(IBehaviorContext context, Action<T> messageConstructor, PublishOptions options)
     {
-        return Publish(context, typeof(T), messageMapper.CreateInstance(messageConstructor), options);
+        return Publish(context, typeof(T), messageMapper.CreateInstance(messageConstructor)!, options);
     }
 
     public Task Publish(IBehaviorContext context, object message, PublishOptions options)
     {
-        var messageType = messageMapper.GetMappedTypeFor(message.GetType());
+        var messageType = messageMapper.GetMappedTypeFor(message.GetType()) ?? message.GetType();
 
         return Publish(context, messageType, message, options);
     }
 
     async Task Publish(IBehaviorContext context, Type messageType, object message, PublishOptions options)
     {
         var messageId = options.UserDefinedMessageId ?? CombGuid.Generate().ToString();
-        var headers = new Dictionary<string, string>(options.OutgoingHeaders)
+        var headers = new Dictionary<string, string?>(options.OutgoingHeaders)
         {
             [Headers.MessageId] = messageId
         };
@@ -106,20 +108,20 @@ public async Task Unsubscribe(IBehaviorContext context, Type eventType, Unsubscr
 
     public Task Send<[DynamicallyAccessedMembers(IMessageCreator.CreatorMembersRequired)] T>(IBehaviorContext context, Action<T> messageConstructor, SendOptions options)
     {
-        return SendMessage(context, typeof(T), messageMapper.CreateInstance(messageConstructor), options);
+        return SendMessage(context, typeof(T), messageMapper.CreateInstance(messageConstructor)!, options);
     }
 
     public Task Send(IBehaviorContext context, object message, SendOptions options)
     {
-        var messageType = messageMapper.GetMappedTypeFor(message.GetType());
+        var messageType = messageMapper.GetMappedTypeFor(message.GetType()) ?? message.GetType();
 
         return SendMessage(context, messageType, message, options);
     }
 
     async Task SendMessage(IBehaviorContext context, Type messageType, object message, SendOptions options)
     {
         var messageId = options.UserDefinedMessageId ?? CombGuid.Generate().ToString();
-        var headers = new Dictionary<string, string>(options.OutgoingHeaders)
+        var headers = new Dictionary<string, string?>(options.OutgoingHeaders)
         {
             [Headers.MessageId] = messageId
         };
@@ -140,20 +142,20 @@ async Task SendMessage(IBehaviorContext context, Type messageType, object messag
 
     public Task Reply(IBehaviorContext context, object message, ReplyOptions options)
     {
-        var messageType = messageMapper.GetMappedTypeFor(message.GetType());
+        var messageType = messageMapper.GetMappedTypeFor(message.GetType()) ?? message.GetType();
 
         return ReplyMessage(context, messageType, message, options);
     }
 
     public Task Reply<[DynamicallyAccessedMembers(IMessageCreator.CreatorMembersRequired)] T>(IBehaviorContext context, Action<T> messageConstructor, ReplyOptions options)
     {
-        return ReplyMessage(context, typeof(T), messageMapper.CreateInstance(messageConstructor), options);
+        return ReplyMessage(context, typeof(T), messageMapper.CreateInstance(messageConstructor)!, options);
     }
 
     async Task ReplyMessage(IBehaviorContext context, Type messageType, object message, ReplyOptions options)
     {
         var messageId = options.UserDefinedMessageId ?? CombGuid.Generate().ToString();
-        var headers = new Dictionary<string, string>(options.OutgoingHeaders)
+        var headers = new Dictionary<string, string?>(options.OutgoingHeaders)
         {
             [Headers.MessageId] = messageId
         };

src/NServiceBus.Testing.Fakes/TestableOutgoingContext.cs

@@ -1,4 +1,6 @@
-namespace NServiceBus.Testing;
+#nullable enable
+
+namespace NServiceBus.Testing;
 
 using System;
 using System.Collections.Generic;
@@ -18,7 +20,7 @@ public partial class TestableOutgoingContext : TestablePipelineContext, IOutgoin
 
     IServiceProvider IBehaviorContext.Builder => GetBuilder();
 
-    IServiceProvider builder = null;
+    IServiceProvider? builder = null;
 
     /// <summary>
     /// Selects the builder returned by <see cref="IBehaviorContext.Builder" />. Override this method to provide your custom
@@ -38,5 +40,5 @@ protected virtual IServiceProvider GetBuilder()
     /// <summary>
     /// The headers of the outgoing message.
     /// </summary>
-    public Dictionary<string, string> Headers { get; set; } = [];
+    public Dictionary<string, string?> Headers { get; set; } = [];
 }