Galaxy: conditionals patterns

This is the runtime-facing map for Galaxy conditional workflow choices. Use it before loading raw survey notes. The survey remains evidence backing; the operation and recipe pages are the actionable references.

Direct Gates

• conditional-run-optional-step — expose or derive a boolean, connect it as inputs.when, and use when: $(inputs.when) to skip optional steps.
• conditional-gate-on-nonempty-result — compute a boolean from empty/non-empty dataset or collection state before gating downstream reporting/export. The MGnify recipe is corpus-backed but clunky pending verified-pattern workflow work.

Routes and Fallbacks

• conditional-route-between-alternative-outputs — run one of several when-gated alternatives, then merge possible outputs with pick_value.
• conditional-transform-or-pass-through — optionally transform a value, then use pick_value to choose transformed output or original fallback.

Not Conditionals

• collection-cleanup-after-mapover-failure — use collection filters when empty or failed mapped elements should be dropped or replaced. This is collection-state cleanup, not a when gate.
• __FILTER_NULL__ — catalog capability for null outputs after conditional steps, but no IWC-backed pattern candidate in the conditionals survey. Zero uptake is not itself an anti-pattern call.

See Also

• iwc-conditionals-survey — conditionals survey and evidence trail.
• galaxy-collection-patterns — companion MOC for collection transforms and cleanup.