optional groups

optional_groups_or joins one copy of the body per blob row with or. optional_groups_and joins with and. The blob argument is declared blob and is a JSON array of objects. [] removes the group.

--(pairs blob, active)--
where optional_groups_or({{pairs}},
  u.id = {{self.id}} and u.active = {{active}}
)

{{self.field}} reads the current row. {{name}} is still an argument from the header. {{self.field}} outside a group is an error. A row field cannot gate optional(...) or optional_when(...).

The body may contain optional(...) and optional_when({{flag}}, ...). optional_when may also wrap the whole group. See Nested.

{{self.ids}}... expands a list stored on that row. A missing field, null, or [] on a rendered row is an error. The compiler does not skip that row.

Nested groups are rejected. The blob placeholder cannot be written with ... and cannot appear in its own body.