Preview an Expression v2

Use the designer's Preview tab to inspect compile-time Expression results without invoking external systems.

Generate Preview data

  1. Save the Workflow so it has a stable key.
  2. Add an Expression to a Step Parameter, Step Return, or Workflow Return.
  3. Pause after editing while the designer validates and compiles the current definition.

Click the Toggle preview mode button to see previews in-situ.

Open the Preview tab to see detail on previews. Click a row to select its Property on the Canvas. Search can highlight matching Step names, Properties, Expressions, or results. Switch search to filter mode to hide non-matching rows.

Interpret an empty result

An empty or null result can be valid. Check:

  • Whether the referenced Workflow Parameter has a useful Sample.
  • Whether the selected Node contract supplies design-time sample data for the Return.
  • Whether the reference path and casing match the declared schema.
  • Whether the function returns an empty or null value for an empty source.
  • Whether the value can only be produced by a real external call - preview deliberately does not invoke Nodes.

Resolve unavailable Preview

No preview available means compilation has not produced Preview data. Open the Problems tab and correct the errors showbn there.

See also

See Expression Syntax, Problems Pane, and Test a Workflow Safely.