Introspecting a schema

If you are building on top of PB — a gRPC/Connect framework, a code generator, a schema explorer — you need to enumerate and inspect the messages, enums, services, and extensions in a schema. PB.Schema provides stable introspection helpers that return PB.Schema.Info structs.

The map returned by PB.compile/1 is an internal representation. Its structure is not part of the public API and may change without notice. Always go through the introspection helpers rather than reaching into the compiled map.

Messages, enums, extensions

PB.Schema.list_messages(schema)        # => [%PB.Schema.Info.Message{}, ...]
PB.Schema.fetch_message(schema, :"my.pkg.Person")  # => {:ok, info} | :error
PB.Schema.message!(schema, :"my.pkg.Person")       # => info | raises

PB.Schema.list_enums(schema)
PB.Schema.fetch_enum(schema, :"my.pkg.Role")
PB.Schema.enum!(schema, :"my.pkg.Role")

PB.Schema.list_extensions(schema)
PB.Schema.fetch_extension(schema, :"my.pkg.priority")
PB.Schema.extension!(schema, :"my.pkg.priority")

Each helper accepts either a compiled schema map or a use PB.Schema module.

A message's fields are PB.Schema.Info.Field structs carrying name, number, type, cardinality, presence, and the message-level :projection (see PB.Schema.Projection). Field types are tagged tuples like {:scalar, :int32}, {:message, name}, {:enum, name}, or {:map, key_type, value_type}.

Services and methods

Service definitions are extracted by PB.compile/1 and exposed the same way, including method input/output types and streaming flags — useful for RPC frameworks:

PB.Schema.list_services(schema)
PB.Schema.fetch_service(schema, :"my.pkg.Greeter")
PB.Schema.service!(schema, :"my.pkg.Greeter")

See PB.Schema.Info.Service, PB.Schema.Info.Method for the struct shapes.