Create separate steps/jobs for PR/Forks versus branches

Build Environment
4

Another approach, using filters in the workflows config:

jobs:
  - forks_only:
      filters:
        branches:
          # only from forks
          only: /^pull\/.*$/
  - canonical_repo_only:
      filters:
        branches:
          # only from canonical repository
          # https://stackoverflow.com/a/5334825/358804
          only: /^(?!pull\/).*$/

The advantages here (versus @dtzar’s shell conditionals):

  • It’s using native CircleCI config, rather than having to break out to shell conditionals
  • The jobs are segmented, which is good if you want very different steps between builds from forks vs. the canonical repo

The disadvantages:

  • It’s equally non-intuitive
  • The jobs are segmented, so you kinda have to maintain them in two places (assuming you want the steps to be similar)
  • This doesn’t work for required status checks in GitHub, which expect a consistent name for all pull requests
  • Regular expression lookarounds aren’t supported by all regex engines, so while it works on CircleCI now, it may not in the future if they switch to a different language/engine for parsing the config

Example usage. A future approach that splits the difference would be using optional build steps, but that isn’t possible yet.

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