pre-and-post-steps.md

Pre and post steps

The keys pre-steps and post-steps in jobs are available in configuration version 2.1 and later

All jobs accept two special arguments of type steps: pre-steps and post-steps.

If an orb user invokes a job with one or both of these arguments, the job will run the steps in pre-steps first, before any other steps run, and then it will run the steps in post-steps last, after any other steps run.

Motivation

Pre- and post- steps allow users to be execute steps in a given job's environment without modifying the orb. This is useful, for example, when a user imports a job and wants to upload assets after it completes, or to run some custom setup steps before job execution. Pre- and post- steps allow the user to make these additions without modifying the imported job.

A steps parameter can be used for a similar purpose, passing steps into a job, but it requires that the job be modified with an execution site for the parameter.

Example of using pre- and post-steps

An orb foo might define a job:

# yaml from orb `foo`
jobs:
  bar:
    machine: true
    steps:
      - checkout
      - run:
          command: echo "building"
      - run:
          command: echo "testing"

Then an orb user could use the job as follows:

# config.yml
version: 2.1
orbs:
  foo: somenamespace/foo@1.2
workflows:
  build:
    jobs:
      - foo/bar:
          pre-steps:
            - run:
                command: echo "install custom dependency"
          post-steps:
            - run:
                command: echo "upload artifact to s3"

The resulting configuration would look like this:

version: 2.1
jobs:
  foo/bar:
    machine: true
    steps:
      - run:
          command: echo "install custom dependency"
      - checkout
      - run:
          command: echo "building"
      - run:
          command: echo "testing"
      - run:
          command: echo "upload artifact to s3"
workflows:
  build:
    jobs:
      - foo/bar