Pass outputs between plugs

A plug can publish named string values with ctx.setOutput. The plugs listed after it read them as ${{ setup.<id>.outputs.<name> }}, so the plug that publishes needs an id.

Read an output in a later plug

blaise:git/worktree publishes the path and branch of the worktree it creates. Use them in a later plug:

version: 1
setup:
  - id: checkout
    use: blaise:git/worktree
  - use: blaise:env
    with:
      vars:
        WORKTREE: ${{ setup.checkout.outputs.path }}
        BRANCH: ${{ setup.checkout.outputs.branch }}

Publish an output from a script

With blaise:shell, append name=value lines to the file in $BLAISE_OUTPUT:

- id: database
  use: blaise:shell
  with:
    start: |
      docker compose up -d db
      echo "url=postgres://localhost:5432/app" >> "$BLAISE_OUTPUT"
- use: blaise:env
  with:
    vars:
      DATABASE_URL: ${{ setup.database.outputs.url }}

Things to know

• A plug can only read the outputs of plugs before it. A reference to a later or unknown id is an error when the configuration loads.
• A plug's with: is evaluated when the plug before it calls next(), so it sees outputs published by every plug that already ran.
• Outputs are strings. Nothing is stored between runs: a plug re-publishes its outputs on every run (a resume script repeats what start published, often through a YAML anchor).
• A plug that is skipped in a run publishes nothing. In a teardown that happens later, the plugs that only have an onSession do not run, so their outputs are empty there.