serverless.template file sometimes changes package type to Zip from Image

[benny-yamagata]

Describe the bug

Occasionally, after building the function locally I will notice a change in my source control tab in VS code for the serverless.template file. It will have changed my package type from image to zip and added additional fields to support it.

Nowhere else in my project is the word zip found, I'm wondering if this is some background process?

Expected Behavior

serverless.template does not change package type.

Current Behavior

serverless.template sometimes changes package type from image to zip. (does not happen the other way around)

Reproduction Steps

1. dotnet new serverless.annotations
2. Replace Functions.cs with the following:

/// <summary>
/// A collection of sample Lambda functions that provide a REST api for doing simple math calculations. 
/// </summary>
public class Functions
{
    [LambdaFunction()]
    public void ProcessDynamoDbEvent(DynamoDBEvent dynamoEvent, ILambdaContext context)
    {
        context.Logger.LogInformation("Processing event");
    

3. Update serverless.template file to change PackageType to Image
4. Add new class to bottom of Functions.cs
5. Build the project

Possible Solution

No response

Additional Information/Context

No response

Targeted .NET platform

.net8

CLI extension version

Package Id                                     Version         Commands
----------------------------------------------------------------------------------------
amazon.lambda.tools                            5.9.0           dotnet-lambda

Environment details (OS name and version, etc.)

OSX Sonoma 14.6.1

[benny-yamagata]

Updated description to include better repro steps

[bhoradc]

Hi @benny-yamagata,

Thank you for reporting the issue. I am able to reproduce this scenario.

When I update the serverless.template file as below to change PackageType to Image, it reverts back to Zip type.

serverless.template

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::Serverless-2016-10-31",
  "Description": "An AWS Serverless Application.  This template is partially managed by Amazon.Lambda.Annotations (v1.3.0.0).",
  "Resources": {
    "LambdaToolsIssue333FunctionsProcessDynamoDbEventGenerated": {
      "Type": "AWS::Serverless::Function",
      "Metadata": {
        "Tool": "Amazon.Lambda.Annotations"
      },
      "Properties": {
        "MemorySize": 512,
        "Timeout": 30,
        "Policies": [
          "AWSLambdaBasicExecutionRole"
        ],
        "PackageType": "Image",
        "ImageUri": "."
      }
    }
  },
  "Outputs": {
    "ApiURL": {
      "Description": "API endpoint URL for Prod environment",
      "Value": {
        "Fn::Sub": "https://${ServerlessHttpApi}.execute-api.${AWS::Region}.amazonaws.com/"
      }
    }
  }
}

When I explicitly specify the PackageType in the LambdaFunction attribute as below, serverless.template file reflects the correct configuration for the Image packagetype and retains it.

[LambdaFunction(PackageType = LambdaPackageType.Image)]

I will further check on why manually updating the packagetype inside serverless.template doesn't work as expected.

Regards,
Chaitanya

[bhoradc]

Hello @benny-yamagata,

I checked with the team to find out that the PackageType property must always be set via the Lambda Annotations attribute.

Any Lambda function property that can be set via the LambdaFunction attribute should be set via the attribute.

Therefore, using below setting would be the ideal way to update the default PackageType to Image.

[LambdaFunction(PackageType = LambdaPackageType.Image)]

And I can confirm that this configuration works as expected, kindly confirm if this helps.

Regards,
Chaitanya

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[benny-yamagata]

Ok makes sense!

The other behavior should be documented somewhere, that if you dont set the annotation package type, it will always be changed. Otherwise it looks like phantom changes from nowhere.