Module osd 

OSD (Omnist Schema Definition) – the text language for the crate::schema model. Ported from ~/dev/omnist/omnist/osd.py.

Grammar (informal):

schema      := record* 'root' NAME
record      := 'record' NAME '{' field (',' field)* ','? '}'
field       := STRING cardinality? ':' type
cardinality := '[' INT? (',' INT?)? ']'   -- [m,n] [m,] [,n] [n]; absent = [1,1]
type        := SCALARNAME '?'? | NAME     -- one scalar, or one Ref

Quoting rule: a "quoted" token is always a field label (data string); an unquoted identifier is always a schema name (scalar keyword or Ref). There is no value-domain composition (no |, enum, literal fields, or union).

The any keyword

Python’s osd.py recognizes "any" as a reserved type keyword and parses it to ANY (RESERVED_TYPE_NAMES = SCALAR_NAMES | {"any"}). This module mirrors that: any in a type position parses to crate::schema::FieldType::Any, and – exactly like Python – any is still a reserved name that cannot be used as a record name (matching the grammar). Since Any already includes null, a trailing ? after any ("a": any?) is a SchemaError (“redundant”), not silently accepted.

Functions

parse_schema

Parse OSD text into a Schema.

to_osd

Serialize a Schema back to OSD text. Ported from Python’s osd.to_osd/_record/_field/_card/_type.