v0.12.0

Changelog

Added

• A string step parameter can list the values it takes. A manifest declares
  allocate: {type: string, values: [none, revenue, units], default: none}, and a value
  outside the list, such as allocate: revenu, is refused with a StepError that names
  the allowed values, whether a step wiring sets it or a field mapping or repair recipe
  calling a sql_macro does. Before, a misspelled value compiled and the
  step ran whichever branch its body fell through to. A manifest is refused if its
  default is not one of its values, or if a parameter that is not a string declares
  them. (#403)
• A step input can be optional, so one step serves projects with and without a
  source. A sql_model declares it optional: true with typed columns:,
  and a wiring may leave it out. The body reads it by name, as the bound relation,
  which must carry those columns, or unbound as an empty relation of them. (#402)

Fixed

• An entity field no mapping produces is a NULL column of its silver model. It was
  left out, so a step whose input requires it compiled and then failed on the engine
  (Binder Error: … does not have a column named …). The column is now typed NULL, as a
  field only some of a merged entity's sources map already was, so marts and the semantic
  layers carry it too. Three kinds stay out: a required field the one mapping omits, a
  vector field, and a field spelled as a canonical that a mapped field links, which a
  metric's filter would otherwise read as written. A step that requires one of them is
  refused at compile. (#404)