[drone] `DRONE_` and `CI_` variable references must convert to a Harness expressions

[jimsheldon]

Drone provides many variables that can be referenced in pipelines, see https://docs.drone.io/pipeline/environment/reference/ and https://github.com/drone/runner-go/blob/master/environ/environ.go

Harness CI does not support environment variables outside of shell command execution, so we must convert them to expressions.

Here is an example Drone pipeline:

name: default
type: docker
kind: pipeline

steps:
  - name: example
    image: busybox
    commands:
    - echo this is build number $DRONE_BUILD_NUMBER

  - name: publish
    image: plugins/docker
    settings:
      repo: gcr.io/example/repo
      tag: 1.0.${DRONE_BUILD_NUMBER}

This should convert to this v1 yaml:

options: {}
stages:
- name: default
  spec:
    clone: {}
    runtime:
      spec: {}
      type: machine
    steps:
    - name: example
      spec:
        image: busybox
        run: echo this is build number <+pipeline.sequenceId>
    - name: publish
      spec:
        image: plugins/docker
        with:
          repo: gcr.io/example/repo
          tag: 1.0.<+pipeline.sequenceId>
      type: plugin
  type: ci

Relevant Harness documentation:

• https://developer.harness.io/docs/platform/variables-and-expressions/harness-variables/
• https://developer.harness.io/docs/platform/pipelines/w_pipeline-steps-reference/triggers-reference

We should convert DRONE_ and CI_ variables surrounded by {} and without.

Where possible, we should reference codebase.* values, since they are always available to pipelines with a codebase defined. trigger.* values are not available for manual pipeline executions.

We need to make an effort to support Drone's substitution logic https://docs.drone.io/pipeline/environment/substitution/#string-operations

Drone variables can be escaped, see https://docs.drone.io/pipeline/environment/substitution/#escaping. This conversion should detect these escaped variables as well.

This table shows all DRONE_ variables, the associated deprecated CI_ variable (if applicable) and the equivalent Harness expression (if it is known).

DRONE_ variable	CI_ variable	Harness expression
DRONE_BRANCH	n/a	<+codebase.branch>
DRONE_BUILD_ACTION	n/a	?
DRONE_BUILD_CREATED	CI_BUILD_CREATED	?
DRONE_BUILD_EVENT	CI_BUILD_EVENT	?
DRONE_BUILD_FINISHED	CI_BUILD_FINISHED	?
DRONE_BUILD_LINK	CI_BUILD_LINK	?
DRONE_BUILD_NUMBER	CI_BUILD_NUMBER	<+pipeline.sequenceId>
DRONE_BUILD_PARENT	n/a	?
DRONE_BUILD_STARTED	CI_BUILD_STARTED	?
DRONE_BUILD_STATUS	CI_BUILD_STATUS	?
DRONE_BUILD_TRIGGER	n/a	?
DRONE_CALVER	n/a	?
DRONE_COMMIT	n/a	?
DRONE_COMMIT_AFTER	n/a	?
DRONE_COMMIT_AUTHOR	CI_COMMIT_AUTHOR	<+codebase.gitUserId>
DRONE_COMMIT_AUTHOR_AVATAR	CI_COMMIT_AUTHOR_AVATAR	?
DRONE_COMMIT_AUTHOR_EMAIL	CI_COMMIT_AUTHOR_EMAIL	?
DRONE_COMMIT_AUTHOR_NAME	CI_COMMIT_AUTHOR_NAME	?
DRONE_COMMIT_BEFORE	n/a	?
DRONE_COMMIT_BRANCH	CI_COMMIT_BRANCH	<+codebase.branch>
DRONE_COMMIT_LINK	n/a	?
DRONE_COMMIT_MESSAGE	CI_COMMIT_MESSAGE	?
DRONE_COMMIT_REF	CI_COMMIT_REF	?
DRONE_COMMIT_SHA	CI_COMMIT_SHA	<+codebase.commitSha>
DRONE_DEPLOY_TO	n/a	?
DRONE_FAILED_STAGES	n/a	?
DRONE_FAILED_STEPS	n/a	?
DRONE_GIT_HTTP_URL	n/a	?
DRONE_GIT_SSH_URL	n/a	?
DRONE_PULL_REQUEST	n/a	<+codebase.prNumber>
DRONE_PULL_REQUEST_TITLE	n/a	<+codebase.prTitle>
DRONE_REMOTE_URL	CI_REMOTE_URL	<+codebase.repoUrl>
DRONE_REPO	CI_REPO	?
DRONE_REPO_BRANCH	n/a	?
DRONE_REPO_LINK	CI_REPO_LINK	?
DRONE_REPO_NAME	CI_REPO_NAME	<+<+codebase.repoUrl>.substring(<+codebase.repoUrl>.lastIndexOf('/') + 1)>"
DRONE_REPO_NAMESPACE	n/a	?
DRONE_REPO_OWNER	n/a	?
DRONE_REPO_PRIVATE	CI_REPO_PRIVATE	?
DRONE_REPO_SCM	n/a	?
DRONE_REPO_VISIBILITY	n/a	?
DRONE_SEMVER	n/a	?
DRONE_SEMVER_BUILD	n/a	?
DRONE_SEMVER_ERROR	n/a	?
DRONE_SEMVER_MAJOR	n/a	?
DRONE_SEMVER_MINOR	n/a	?
DRONE_SEMVER_PATCH	n/a	?
DRONE_SEMVER_PRERELEASE	n/a	?
DRONE_SEMVER_SHORT	n/a	?
DRONE_SOURCE_BRANCH	n/a	?
DRONE_STAGE_ARCH	n/a	?
DRONE_STAGE_DEPENDS_ON	n/a	?
DRONE_STAGE_FINISHED	n/a	?
DRONE_STAGE_KIND	n/a	?
DRONE_STAGE_MACHINE	n/a	?
DRONE_STAGE_NAME	n/a	?
DRONE_STAGE_NUMBER	n/a	?
DRONE_STAGE_OS	n/a	?
DRONE_STAGE_STARTED	n/a	?
DRONE_STAGE_STATUS	n/a	?
DRONE_STAGE_TYPE	n/a	?
DRONE_STAGE_VARIANT	n/a	?
DRONE_STEP_NAME	n/a	?
DRONE_STEP_NUMBER	n/a	?
DRONE_SYSTEM_HOST	n/a	?
DRONE_SYSTEM_HOSTNAME	n/a	?
DRONE_SYSTEM_PROTO	n/a	?
DRONE_SYSTEM_VERSION	n/a	?
DRONE_TAG	n/a	?
DRONE_TARGET_BRANCH	n/a	?
DRONE_WORKSPACE	n/a	?

[jimsheldon]

Bash-like substitutions:

Tested successfully

Print the first 8 characters of the commit sha

Drone	Harness
${DRONE_COMMIT_SHA:0:8}	<+codebase.commitSha.substring(0,8)>

Strip v prefix from v1.0.0

Drone	Harness
${DRONE_TAG##v}	<+<+trigger.payload.ref.split('/')[2]>.substring(<+trigger.payload.ref.split('/')[2]>.indexOf('v') + 1)>

Replace / with -

Drone	Harness
${DRONE_BRANCH/\//-}	<+codebase.branch.replace('/', '-')>

[jimsheldon]

Initial support added in #118.

We are making progress on this, I'll keep this open since we will likely add support for more variables, this issue can be the source of truth for all substitutions.