Conditions

Add if: to a step to run it only when a condition holds:

tasks:
  lab-check:
    steps:
      - run: echo "lab coats on"
        if: '{{ eq .CATEGORY "science" }}'
      - run: echo "let's go"

$ hobnob lab-check CATEGORY=science
run: [lab-check] echo "lab coats on"
[lab-check] lab coats on
run: [lab-check] echo "let's go"
[lab-check] let's go
✓ [lab-check] done

$ hobnob lab-check CATEGORY=history
run: [lab-check] skipped (if: false)
run: [lab-check] echo "let's go"
[lab-check] let's go
✓ [lab-check] done

How a condition works

if: is a shell command. hobnob fills in its template, runs it, and runs the step only if the command succeeds (exits with 0).

The template above becomes true or false, and the shell has commands with those names, so that's all it takes. hobnob's comparisons are eq, ne, lt, le, gt and ge. They compare numbers as numbers, so {{ gt (.QUESTIONS | len) 5 }} works as you'd expect. The comparisons table explains how each type compares.

Because it's a shell command, any shell test works too, such as checking whether a file exists:

tasks:
  import:
    steps:
      - run: ./import.sh questions.json
        if: '[ -f questions.json ]'

Skipping a whole task

Put if: on the task itself to skip all its steps:

tasks:
  explain-answer:
    if: '{{ eq .CATEGORY "science" }}'
    steps:
      - run: echo "here is the science behind it"
      - set:
          - EXPLAINED: "yes"

$ hobnob explain-answer CATEGORY=history
⊘ [explain-answer] skipped
✓ [explain-answer] done

Calling a task that skips

A skipped task isn't an error, but its steps don't run, so it sets nothing. When explain-answer skips, EXPLAINED is never set, so a caller reading it needs | default:

tasks:
  quiz:
    steps:
      - call: explain-answer
        into:
          - EXPLAINED: .EXPLAINED | default "no"

Rules

• Prefer comparisons to shell tests for variables. A variable goes into the shell command as plain text, as in a command written as text. In '[ "{{.CATEGORY}}" = "science" ]', a CATEGORY holding a " breaks the command, and the step is skipped without an error. {{ eq .CATEGORY "science" }} can't break this way. If you need a shell test, escape the value with quote.
• if: runs in the task's working directory, even on a step with its own dir:.