Change set display doesn't follow --output flag

[dboitnot]

Change set display doesn't follow --output flag

Despite being referenced in update.py, it appears that the ChangeSet display does not use the setting from the --output flag.

Your environment

• Sceptre, version 2.7.0
• Python 3.8.2
• Environment: python:3.8.2-slim docker image

Steps to reproduce

sceptre --output=yaml update -c ban/banner-app-image-build.yaml
[2021-12-05 16:45:57] - ban/banner-app-image-build - Successfully initiated creation of Change Set 'change-set-d167800455ea11ec86ff0242ac110002'
{'ChangeSetName': 'change-set-d167800455ea11ec86ff0242ac110002', 'StackName': 's-ban-banner-app-image-build', 'CreationTime': datetime.datetime(2021, 12, 5, 16, 45, 57, 184000, tzinfo=tzlocal()), 'ExecutionStatus': 'AVAILABLE', 'Status': 'CREATE_COMPLETE', 'Changes': [{'ResourceChange': {'Action': 'Modify', 'LogicalResourceId': 'CodeBuildProject', 'PhysicalResourceId': 'banner-app', 'ResourceType': 'AWS::CodeBuild::Project', 'Replacement': 'Conditional', 'Scope': ['Properties']}}]}

Expected behaviour

ChangeSet should be displayed in YAML format.

Actual behaviour

ChangeSet is displayed in JSON format.

Notes

The output flag is clearly being parsed, because if a malformed value is provided we get an error:

$ sceptre --output=yamll update -c ban/banner-app-image-build.yaml
Usage: sceptre [OPTIONS] COMMAND [ARGS]...
Try 'sceptre --help' for help.

Error: Invalid value for '--output': 'yamll' is not one of 'text', 'yaml', 'json'.

Further, since this is an interactive process, we don't expect this output to be machine-parsed. I'd therefore think that YAML, being vastly more readable, would be a better default.

Possibly, I'm misunderstanding the purpose of the --output flag, because if I force the value to yaml in update.py I still get JSON output:

            # Describe changes
            descriptions = plan.describe_change_set(change_set_name)
            for description in list(descriptions.values()):
                if not verbose:
                    description = simplify_change_set_description(description)
                write(description, 'yaml')

For what it's worth, I made the following patch:

            # Describe changes
            descriptions = plan.describe_change_set(change_set_name)
            for description in list(descriptions.values()):
                if not verbose:
                    description = simplify_change_set_description(description)

                write('-'*80,'text')
                write(yaml.dump(description), 'text')
                write('-'*80,'text')

I think the output is an improvement:

sceptre  update -c ban/banner-app-image-build.yaml                                             [17:19:43]
[2021-12-05 17:19:53] - ban/banner-app-image-build - Successfully initiated creation of Change Set 'change-set-8efdd8f855ef11ec8b790242ac110002'
--------------------------------------------------------------------------------
ChangeSetName: change-set-8efdd8f855ef11ec8b790242ac110002
Changes:
- ResourceChange:
    Action: Modify
    LogicalResourceId: CodeBuildProject
    PhysicalResourceId: banner-app
    Replacement: Conditional
    ResourceType: AWS::CodeBuild::Project
    Scope:
    - Properties
CreationTime: 2021-12-05 17:19:53.227000+00:00
ExecutionStatus: AVAILABLE
StackName: sig-ban-banner-app-image-build
Status: CREATE_COMPLETE

--------------------------------------------------------------------------------
Proceed with stack update? [y/N]:

[zaro0508]

could you please propose your patch as a PR @dboitnot?

[dboitnot]

Added PR #1183

[jfalkenstein]

This seems related to #1173

[dboitnot]

This is no longer an issue in the current version of Sceptre.