sam: cdk diff returns nothing when codeUri or events are changed

[pahud]

Describe the bug

cdk diff returns nothing when I change the codeUri or events prop of sam.CfnFunction

 new sam.CfnFunction(this,`MarkLogicErrAlertFunction`,{
      codeUri: 's3://my-bucket/HelloWorldLambda12345.zip',
      handler: 'index.handler',
      runtime: 'nodejs16.x',
      // timeout: 300,
      // functionName: mailerfunctionName,
      // events: {
      //   TaskServerError: {
      //     properties: TaskServerErrorProperties,
      //     type: 'CloudWatchLogs',
      //   },

Expected Behavior

cdk diff should return the change

Current Behavior

it returns nothing

Reproduction Steps

Just deploy this for the first time

 new sam.CfnFunction(this,`MarkLogicErrAlertFunction`,{
      codeUri: 's3://my-bucket/HelloWorldLambda12345.zip',
      handler: 'index.handler',
      runtime: 'nodejs16.x',
      // timeout: 300,
      // functionName: mailerfunctionName,
      // events: {
      //   TaskServerError: {
      //     properties: TaskServerErrorProperties,
      //     type: 'CloudWatchLogs',
      //   },

and then modify codeUri or events, run cdk diff again.

Possible Solution

No response

Additional Information/Context

No response

CDK CLI Version

v2.126.0

Framework Version

No response

Node.js Version

v18.16.0

OS

mac

Language

TypeScript

Language Version

No response

Other information

No response

[pahud]

internal tracking: V1258335352

[mrgrain]

With the new change set based diff implemented in #28336 we are asking the CFN service for a list of changes. However the changes reported by CFN look like this:

[
  {
    "type": "Resource",
    "resourceChange": {
      "action": "Modify",
      "logicalResourceId": "MyFunction",
      "physicalResourceId": "SamStack-MyFunction-1234",
      "resourceType": "AWS::Lambda::Function",
      "replacement": "False",
      "scope": [
        "Properties"
      ],
      "details": [
        {
          "target": {
            "attribute": "Properties",
            "name": "Code",
            "requiresRecreation": "Never"
          },
          "evaluation": "Static",
          "changeSource": "DirectModification"
        }
      ]
    }
  }
]

Most notably, they are pointing to changes in a lambda function. This lambda function does not exists in the local template, since locally we have a SAM Function. Thus the diff tool fails to connect the reported diff the local template and silently drops the change.

[mrgrain]

Arguably the --no-change-set diff is better in this case:

➜  sam git:(main) ✗ cdk diff --no-change-set
Stack SamStack
Resources
[~] AWS::Serverless::Function MyFunction MyFunction replace
 └─ [~] CodeUri (requires replacement)
     ├─ [-] s3://my-bucket/HelloWorldLambda12345.zip
     └─ [+] s3://my-bucket/HelloWorldLambda.zip


✨  Number of stacks with differences: 1

[github-actions]

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