Issue with BitBucket pipeline YAML syntax

Question

I have created a bitbucket-pipelines.yml file to test a powershell script that can run on remote AWS instance.

image: python:3.5.1

pipelines:
  custom:
    default:
      - step:
          caches:
            - pip
          script:
            - pip install awscli
            - aws ssm send-command --document-name "AWS-RunRemoteScript" --instance-ids "i-xxxxx" --parameters '{"sourceType":["S3"],"sourceInfo":["{\"path\": \"https://s3.us-east-2.amazonaws.com/my-bucket-name/test.ps1\"}"],"executionTimeout":["3600"]}' --timeout-seconds 600 --region us-east-2

When i try running it, i get the following error message for the last line:

The 'script' section in your bitbucket-pipelines.yml file must be a list of strings

I checked the syntax with other online YAML validators and it shows fine. Not sure why BitBucket is having issue. Any pointers?

Answer 1

The second item in your list contains a colon followed by a space, which makes it a mapping in YAML.

In such cases you need to quote it. However, you already use single and double quotes and want to avoid adding more backslashes.

I prefer using block scalars for longer strings:

      script:
        - pip install awscli
        - >-
          aws ssm send-command
          --document-name "AWS-RunRemoteScript"
          --instance-ids "i-xxxxx"
          --parameters '{"sourceType":["S3"],"sourceInfo":["{\"path\":
          \"https://s3.us-east-2.amazonaws.com/my-bucket-name/test.ps1\"}"],
          "executionTimeout":["3600"]}'
          --timeout-seconds 600 --region us-east-2

This is a so called folded block scalar, meaning all its lines will be folded together with spaces.

May I recommend my article on quoting strings in YAML where all this is explained in detail? http://blogs.perl.org/users/tinita/2018/03/strings-in-yaml---to-quote-or-not-to-quote.html