validate does not return useful messages

[ranman]

Given a template:

AWSTemplateFormatVersion : '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Resources:
  VoteSpacesTabs:
    Type: "AWS::Serverless::Function"
    Properties:
      Runtime: python3.6
      Handler: lambda_function.lambda_handler
      Policies: AmazonDynamoDBFullAccess
      Environment:
        Variables:
          TABLE_NAME: !Ref VotesTable
      Events:
        Vote:
          Type: Api
          Properties:
            Path: /vote
            Method: post

Invoking:
sam validate
returns:
Valid!

Should it return valid given that we have no code-uri or other required attributes? What exactly is it validating?

Given this template:

AWSTemplateFormatVersion : '2010-09-09'
Transform: AWS::Serverless-2016-10-31
Resources:
  VotesTable:
    Type: "AWS::Serverless::SimpleTable"
  VoteSpacesTabs:
    Type: "AWS::Serverless::Function"
    Properties:
      Runtime: python3.6
      Handler: lambda_function.lambda_handler
      Policies: AmazonDynamoDBFullAccess
      Environment:
        Variables:
          TABLE_NAME: !Ref VotesTable
      Events:
        Vote:
          Type: Api
          Properties:
            Path: /vote
            Method: post

Invoking
sam validate
Returns:
ERROR: Failed to read the resources line numbers. This usually means that the template contains invalid indentation. Please check it and try again

This error message isn't helpful in determining what's wrong. I still haven't figured out what's wrong.

However both templates are valid from the point of view of cloudformation:
aws cloudformation validate-template --template-body file://template.yaml

[PaulMaddox]

Should it return valid given that we have no code-uri or other required attributes? What exactly is it validating?

Currently it validates against the SAM language specification - you can see this is you put Runtime: blah for example, you'll get the following validation error:

ERROR: Resource "VoteSpacesTabs", property "Runtime": Invalid value Blah. Valid values are "nodejs", "nodejs4.3", "nodejs6.10", "java8", "python2.7", "python3.6", "dotnetcore1.0", "nodejs4.3-edge" (line: 9; col: 6)

CodeUri specifically is a required parameter, but only for packaged templates. As such, it doesn't make much sense to highlight this as a hard error in a template that might still be in progress (sam validate is designed to be integrated into IDE's as a linting tool too).

ERROR: Failed to read the resources line numbers. This usually means that the template contains invalid indentation. Please check it and try again
This error message isn't helpful in determining what's wrong. I still haven't figured out what's wrong.

I dug into this and it's two problems:

• Our SAM parser (wrongly) assumes there won't be a resource without a Properties section defined.
• Instead of giving you a useful error, its masked by a really generic error that doesn't help.

I'm working on a fix for both.

[PaulMaddox]

Fixed in b673757

[ranman]

I don't think that's the right commit.

[badfun]

I'm getting the same error with a template created by CodeStar. The template works fine, but running validate returns the error.