[Bitbucket Pipeline] Handle a repository-dependent dynamic step environment variable with default value from package.json version

README.md

PROBLEM

When, for example, you are sharing a step between a custom and a branch pipeline which requires a variable to be set, then you can set this variable in the custom pipeline with a custom manual pipeline variable ↑, but this leaves the variable unset in the branch pipelines.

SOLUTION

If the VERSION variable is a static value in the branch pipelines, you can set it in the workspace ↑, deployment ↑ or repository ↑ variables configuration. But if it is a dynamic value, based on your repository content, then shell parameter expansion ↑ allows to set a default based on a command when the variable is empty or null.

EXAMPLE

In the example bitbucket-pipelines.yml, the "deploy" step uses the mandatory VERSION variable. The custom pipeline "manual-deploy" sets this variable by using a custom manual pipeline variable, even with a default of latest, which is displayed in the Bitbucket GUI ↑. The branch pipeline "main" cannot set the variable. Because of the package.json file with a "version" key set in the repository, which will be used as a default.

• In the "deploy" step, the VERSION variable is set to the version defined in the package.json file, when it is empty or null.
• The ":" colon null utility ↑ prevents executing the result of the expansion.
• The "jq" tool is part of the Atlassian default image ↑.
• The "--raw-output" option ↑ removes quotes from the returned JSON string.
• The ".version" object identifier-index filter ↑ returns the value at the JSON object key "version".

bitbucket-pipelines.yml

image: atlassian/default-image:4

definitions:
  steps:
    - step: &deploy
      name: 'Deploy Application'
      script:
        - : ${VERSION:=$(jq --raw-output '.version' package.json)}
        - echo ${VERSION}

pipelines:
  custom:
    manual-deploy:
      - variables:
        - name: VERSION
          default: latest
      - step: *deploy
        
  branches:
    main:
      - step: *deploy

package.json

{
  "version": "1.2.3"
}