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Expose ILambdaSerializer on ILambdaContext #2378

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69f9619
Expose ILambdaSerializer on ILambdaContext
GarrettBeatty May 14, 2026
9c9fdbb
Address PR review feedback
GarrettBeatty May 15, 2026
b6d5159
Address Copilot PR review feedback
GarrettBeatty May 15, 2026
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25 changes: 25 additions & 0 deletions .autover/changes/6e13a012-1f93-4e55-90b5-d2dd480d086c.json
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Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
{
"Projects": [
{
"Name": "Amazon.Lambda.Core",
"Type": "Minor",
"ChangelogMessages": [
"Add ILambdaSerializer Serializer property to ILambdaContext (default-implemented to null on net8.0+) so user code can access the serializer registered with the runtime"
]
},
{
"Name": "Amazon.Lambda.RuntimeSupport",
"Type": "Minor",
"ChangelogMessages": [
"Expose the registered ILambdaSerializer on HandlerWrapper.Serializer and propagate it to the per-invocation ILambdaContext.Serializer"
]
},
{
"Name": "Amazon.Lambda.TestUtilities",
"Type": "Minor",
"ChangelogMessages": [
"Add Serializer setter to TestLambdaContext to mirror the new ILambdaContext.Serializer property"
]
}
]
}
20 changes: 20 additions & 0 deletions Libraries/src/Amazon.Lambda.Core/ILambdaContext.cs
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@@ -1,6 +1,7 @@
namespace Amazon.Lambda.Core
{
using System;
using System.Diagnostics.CodeAnalysis;

/// <summary>
/// Object that allows you to access useful information available within
Expand Down Expand Up @@ -95,6 +96,25 @@ public interface ILambdaContext
/// The trace id generated by Lambda for distributed tracing across AWS services.
/// </summary>
string TraceId { get { return string.Empty; } }

/// <summary>
/// The <see cref="ILambdaSerializer"/> the Lambda function registered with the
/// runtime — either the instance passed to
/// <c>LambdaBootstrapBuilder.Create(handler, serializer)</c> /
/// <c>HandlerWrapper.GetHandlerWrapper(handler, serializer)</c>, or the type set
/// via <c>[assembly: LambdaSerializer(typeof(...))]</c> in class-library mode.
/// User code can reuse it for ad-hoc (de)serialization without re-instantiating.
/// Can be null when the function did not register a serializer (e.g., raw-stream
/// handlers).
/// </summary>
/// <remarks>
/// <para><b>Preview API.</b> Class-library mode requires an updated managed
/// Lambda runtime to populate this property; until that ships, the value will
/// be null when running in class-library mode. The <see cref="ExperimentalAttribute"/>
/// is applied to surface this caveat at the call site.</para>
/// </remarks>
[Experimental("AWSLAMBDA001")]
ILambdaSerializer Serializer { get { return null; } }
#endif
}
}
48 changes: 28 additions & 20 deletions Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/HandlerWrapper.cs
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Expand Up @@ -36,6 +36,14 @@ public class HandlerWrapper : IDisposable
/// </summary>
public LambdaBootstrapHandler Handler { get; private set; }

/// <summary>
/// The serializer registered with the wrapper, if any. Surfaced so the
/// runtime bootstrap can attach it to the per-invocation
/// <see cref="ILambdaContext"/>, allowing user code to reuse it.
/// Null for handlers that don't take a typed input/output.
/// </summary>
public ILambdaSerializer Serializer { get; private set; }

private HandlerWrapper(LambdaBootstrapHandler handler)
{
Handler = handler;
Expand Down Expand Up @@ -121,7 +129,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Func<TInput, Task> handle
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
await handler(input);
return EmptyInvocationResponse;
});
}) { Serializer = serializer };
}

/// <summary>
Expand Down Expand Up @@ -171,7 +179,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Func<TInput, ILambdaConte
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
await handler(input, invocation.LambdaContext);
return EmptyInvocationResponse;
});
}) { Serializer = serializer };
}

/// <summary>
Expand Down Expand Up @@ -218,7 +226,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Func<TInput, Task<Stream>
{
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
return new InvocationResponse(await handler(input));
});
}) { Serializer = serializer };
}

/// <summary>
Expand Down Expand Up @@ -265,7 +273,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Func<TInput, ILambdaConte
{
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
return new InvocationResponse(await handler(input, invocation.LambdaContext));
});
}) { Serializer = serializer };
}

/// <summary>
Expand All @@ -278,7 +286,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Func<TInput, ILambdaConte
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Task<TOutput>> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = async (invocation) =>
{
TOutput output = await handler();
Expand All @@ -300,7 +308,7 @@ public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Task<TOutput>> hand
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Stream, Task<TOutput>> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = async (invocation) =>
{
TOutput output = await handler(invocation.InputStream);
Expand All @@ -322,7 +330,7 @@ public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Stream, Task<TOutpu
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TInput, TOutput>(Func<TInput, Task<TOutput>> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = async (invocation) =>
{
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
Expand All @@ -345,7 +353,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput, TOutput>(Func<TInput, Tas
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<ILambdaContext, Task<TOutput>> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = async (invocation) =>
{
TOutput output = await handler(invocation.LambdaContext);
Expand All @@ -367,7 +375,7 @@ public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<ILambdaContext, Tas
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Stream, ILambdaContext, Task<TOutput>> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = async (invocation) =>
{
TOutput output = await handler(invocation.InputStream, invocation.LambdaContext);
Expand All @@ -389,7 +397,7 @@ public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Stream, ILambdaCont
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TInput, TOutput>(Func<TInput, ILambdaContext, Task<TOutput>> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = async (invocation) =>
{
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
Expand Down Expand Up @@ -449,7 +457,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Action<TInput> handler, I
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
handler(input);
return Task.FromResult(EmptyInvocationResponse);
});
}) { Serializer = serializer };
}

/// <summary>
Expand Down Expand Up @@ -499,7 +507,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Action<TInput, ILambdaCon
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
handler(input, invocation.LambdaContext);
return Task.FromResult(EmptyInvocationResponse);
});
}) { Serializer = serializer };
}

/// <summary>
Expand Down Expand Up @@ -546,7 +554,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Func<TInput, Stream> hand
{
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
return Task.FromResult(new InvocationResponse(handler(input)));
});
}) { Serializer = serializer };
}

/// <summary>
Expand Down Expand Up @@ -593,7 +601,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Func<TInput, ILambdaConte
{
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
return Task.FromResult(new InvocationResponse(handler(input, invocation.LambdaContext)));
});
}) { Serializer = serializer };
}

/// <summary>
Expand All @@ -606,7 +614,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput>(Func<TInput, ILambdaConte
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<TOutput> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = (invocation) =>
{
TOutput output = handler();
Expand All @@ -628,7 +636,7 @@ public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<TOutput> handler, I
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Stream, TOutput> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = (invocation) =>
{
TOutput output = handler(invocation.InputStream);
Expand All @@ -650,7 +658,7 @@ public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Stream, TOutput> ha
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TInput, TOutput>(Func<TInput, TOutput> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = (invocation) =>
{
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
Expand All @@ -673,7 +681,7 @@ public static HandlerWrapper GetHandlerWrapper<TInput, TOutput>(Func<TInput, TOu
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<ILambdaContext, TOutput> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = (invocation) =>
{
TOutput output = handler(invocation.LambdaContext);
Expand All @@ -695,7 +703,7 @@ public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<ILambdaContext, TOu
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Stream, ILambdaContext, TOutput> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = (invocation) =>
{
TOutput output = handler(invocation.InputStream, invocation.LambdaContext);
Expand All @@ -717,7 +725,7 @@ public static HandlerWrapper GetHandlerWrapper<TOutput>(Func<Stream, ILambdaCont
/// <returns>A HandlerWrapper</returns>
public static HandlerWrapper GetHandlerWrapper<TInput, TOutput>(Func<TInput, ILambdaContext, TOutput> handler, ILambdaSerializer serializer)
{
var handlerWrapper = new HandlerWrapper();
var handlerWrapper = new HandlerWrapper { Serializer = serializer };
handlerWrapper.Handler = (invocation) =>
{
TInput input = serializer.Deserialize<TInput>(invocation.InputStream);
Expand Down
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