Missing required field

Some fields have no sensible default — a vspace with no size says nothing, a set with no mark marks nothing. Omitting one is a hard error, caught while shortcuts expand, before any format is written.

What it looks like

::: {.vspace}
:::

ERROR: Shortcut 'vspace' requires size — set it as an attribute. (in .vspace)

The same shape applies to any required field — for example a set with no mark:

ERROR: Shortcut 'set' requires mark — set it as an attribute. (in .set "John Keats")

What it means

The field is the instruction: the size is the whole point of a vspace, the mark is the whole point of a set. There is nothing safe to fall back to, so unlike a bad value (a warning), a missing required field stops the build.

How to fix

Supply the attribute the message names:

::: {.vspace size="medium"}
:::

Each shortcut's required fields are listed in the system shortcut reference. If it's your own shortcut, an interface entry can mark a field required: true or give it a default.

Related

• Invalid attribute value — the field is present but its value isn't accepted.
• Undeclared mark — a set whose mark is present but names a mark you never declared.