# `PB.Schema.Info`
[🔗](https://github.com/hansihe/pb_ex/blob/v0.2.0/pb/lib/pb/schema/info.ex#L159)

Public introspection structs returned by `PB.Schema.fetch_message/2` and
friends.

These structs are a stable, intentionally narrow projection of the internal
compiled schema. Callers should branch off the public structs rather than
reading `schema.messages` directly: the internal compiled representation may
grow new fields or change shape as the runtime evolves.

## Packages

`package` on `Message`, `Enum` and `Service` is the proto package of the
file declaring the type, or `nil` for a file without one. Nested types share
their file's package, so `a.b.Outer.Inner` declared in package `a.b` has
`package: :"a.b"`.

## Options

`options` on `Field` and `Message` is the declaration's
`google.protobuf.FieldOptions` or `google.protobuf.MessageOptions`, decoded
like any other message: standard options under their field names and custom
options under `:__extensions__`, keyed by the extension's full name. It is
`%{}` when the declaration has no options. Custom options whose extension
isn't in the descriptor set stay undecoded under `:__unknown_fields__`.

    field.options[:deprecated]
    #=> true

    PB.Schema.option(field, :"acme.v1.sensitive")
    #=> true

## Field types

`%PB.Schema.Info.Field{}.type` is a tagged tuple:

  * `{:scalar, scalar}` where `scalar` is one of `:double`, `:float`,
    `:int32`, `:int64`, `:uint32`, `:uint64`, `:sint32`, `:sint64`,
    `:fixed32`, `:fixed64`, `:sfixed32`, `:sfixed64`, `:bool`, `:string`,
    `:bytes`.
  * `{:message, message_name}` — a message reference.
  * `{:enum, enum_name}` — an enum reference.
  * `{:map, key_type, value_type}` — only emitted when
    `field.cardinality == :map`; `key_type` and `value_type` are themselves
    tagged tuples following the same shape.

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*Consult [api-reference.md](api-reference.md) for complete listing*