"Incorrect type" for Serverless Application Model condition if filename ends in `.sam.yaml`

[garretwilson]

Describe the bug

The extension is showing an incorrect YAML error, but whether the error is shown depends on the filename of the file being editing—specifically whether the filename is sam.yaml or ends in .sam.yaml.

I'm editing an AWS CloudFormation Serverless Application Model (SAM) YAML file. I have appropriate settings in my settings.json, including (among others) the following:

    "yaml.customTags": [
        "!Equals sequence",
        "!Ref scalar"
    ],

Let's say I have a simple SAM YAML file foo.yaml using language extensions:

AWSTemplateFormatVersion: 2010-09-09
Transform:
  - AWS::LanguageExtensions
  - AWS::Serverless-2016-10-31

Description:
  Foo.

Parameters:
  Foo:
    Description: Some parameter.
    Type: String
    AllowedValues: ['false', 'true']
    Default: 'false'

Conditions:
  IsFoo: !Equals [!Ref Foo, 'true']

That condition shows up just fine in the editor, as expected. But if I change the filename to foo.sam.yaml or sam.yaml, the extension shows an error! In particular !Equals [!Ref Foo, 'true'] is underlined in red, with the following error message:

Incorrect type. Expected "object(AWS CloudFormation Serverless Application Model (SAM))".yaml-schema: AWS CloudFormation Serverless Application Model (SAM)

If I rename the file to foo-sam.yaml or foo.yaml or anything-but-dot-sam.yaml, the error goes away.

I don't believe the filename should influence the linting of the YAML contents.

Environment

• Windows
• Mac
• Linux
• other (please specify)

[garretwilson]

I think I find out why the filename matters. The extension is using JSON schemas from the default schema store catalog, and there SAM is associated with filename extensions like this:

    {
      "name": "AWS CloudFormation Serverless Application Model (SAM)",
      "description": "The AWS Serverless Application Model (AWS SAM, previously known as Project Flourish) extends AWS CloudFormation to provide a simplified way of defining the Amazon API Gateway APIs, AWS Lambda functions, and Amazon DynamoDB tables needed by your serverless application",
      "fileMatch": [
        "template.yaml",
        "serverless.template",
        "*.sam.json",
        "*.sam.yml",
        "*.sam.yaml",
        "sam.json",
        "sam.yml",
        "sam.yaml"
      ],
      "url": "https://raw.githubusercontent.com/aws/serverless-application-model/main/samtranslator/schema/schema.json"
    },

So one mystery solved! It's not a bug that the error occurs only for certain filenames—those are the filenames associated with the schema.

But the actual SAM schema may have a bug that is causing this error. I'll have to look more closely into it. Another day.