get-unknown-root

[wizzard] $get "<path>" does not start with data, ctx, loop. The first segment names where a path
reads from, and any other start evaluates to undefined. Start the path with the root it belongs to,
such as data.<path>. …/errors/get-unknown-root

Returned by validateFlow as a problem whose path is the object holding the $get, such as steps.<id>.when, and listed in the message of flow-invalid by assertFlow. Only a $get the engine evaluates is checked: one in a step’s ui, in a $ref’s args or beside a flow’s steps is your data, and is left alone.

A $get reads a value by a dotted path, and the first segment names where to read from: data for the answers, ctx for what the application supplied, loop for the current item inside a repeat group. A path that starts anywhere else evaluates to undefined, which a when reads as false, so the step silently disappears.

The usual cause is a path written relative to the answers, without its root:

{ "$get": "account.email" }

Prefix it with the root it belongs to:

{ "$get": "data.account.email" }

The roots are described in the expressions guide.