deploy: byte-order-mark (BOM) in existing cf template causes YAMLSyntaxError and fails deployment

[markdchurchill]

Describe the bug

When performing manual tweaks to stacks in the console (eg - migrating resources into nested) users can provide a template that starts with a byte-order-mark and this is accepted by the console.

On subsequent deployments using CDK this causes a deployment failure. Updating the stack in console to remove the BOM fixes the issue.

Expected Behavior

aws-cdk should not have different behaviour to the console upload

Current Behavior

XXXXXXXX: deploying... [1/1]
❌  XXXXXXXXX failed: YAMLSyntaxError: All collection items must start at the same column
    at _Collection.parse (/usr/lib/node_modules/aws-cdk/lib/index.js:401:9191)
    at /usr/lib/node_modules/aws-cdk/lib/index.js:401:28601
    at _Document.parseContents (/usr/lib/node_modules/aws-cdk/lib/index.js:401:13915)
    at _Document.parse (/usr/lib/node_modules/aws-cdk/lib/index.js:401:14863)
    at Object.parse2 [as parse] (/usr/lib/node_modules/aws-cdk/lib/index.js:401:31141)
    at parseDocument (/usr/lib/node_modules/aws-cdk/lib/index.js:423:9258)
    at Object.parse2 (/usr/lib/node_modules/aws-cdk/lib/index.js:423:9537)
    at parseYamlStrWithCfnTags (/usr/lib/node_modules/aws-cdk/lib/index.js:423:12316)
    at deserialize (/usr/lib/node_modules/aws-cdk/lib/index.js:423:1[1915](https://gitlab.XXXXXXXXXXXX))
    at deserializeStructure (/usr/lib/node_modules/aws-cdk/lib/index.js:423:12857) {
  source: [_Collection]
}

Reproduction Steps

• Deploy a simple stack with aws-cdk
• Pull the template json from the console, edit it, add a byte-order-mark, and update the stack
• Attempt to deploy against that stack with aws-cdk

Possible Solution

No response

Additional Information/Context

Important to note that all manual work was done in json, so I assume the yaml error was part of an internal process.

CDK CLI Version

2.136.0 (build 94fd33b)

Framework Version

No response

Node.js Version

v18.20.1

OS

Debian 12

Language

.NET

Language Version

8.0.203

Other information

No response

[pahud]

Pull the template json from the console, edit it, add a byte-order-mark, and update the stack

This seems to be an edge case. Can you explain why you need to do this?

[markdchurchill]

Obviously the BOM isn't being added intentionally - but editors will do this to files. If this is valid CF then cdk should work with it - if it is not valid CF then the console should reject it. At minimum cdk should produce accurate error messages.

This won't catch me out again, but others might not be so lucky to spot the issue.