Crate prost_reflect

This crate provides support for dynamic protobuf messages. These are useful when the protobuf type definition is not known ahead of time.

The main entry points into the API of this crate are:

• DescriptorPool wraps a FileDescriptorSet output by the protobuf compiler to provide an API for inspecting type definitions.
• DynamicMessage provides encoding, decoding and reflection of an arbitrary protobuf message definition described by a MessageDescriptor.

Example - decoding

DynamicMessage does not implement Default since it needs a message descriptor to function. To decode a protobuf byte stream into an instance of this type, use DynamicMessage::decode to create a default value for the MessageDescriptor instance and merge into it:

use prost::Message;
use prost_types::FileDescriptorSet;
use prost_reflect::{DynamicMessage, DescriptorPool, Value};

let pool = DescriptorPool::decode(include_bytes!("file_descriptor_set.bin").as_ref()).unwrap();
let message_descriptor = pool.get_message_by_name("package.MyMessage").unwrap();

let dynamic_message = DynamicMessage::decode(message_descriptor, b"\x08\x96\x01".as_ref()).unwrap();

assert_eq!(dynamic_message.get_field_by_name("foo").unwrap().as_ref(), &Value::I32(150));

Example - JSON mapping

When the serde feature is enabled, DynamicMessage can be deserialized to and from the canonical JSON mapping defined for protobuf messages.

use prost::Message;
use prost_reflect::{DynamicMessage, DescriptorPool, Value};
use serde_json::de::Deserializer;

let pool = DescriptorPool::decode(include_bytes!("file_descriptor_set.bin").as_ref()).unwrap();
let message_descriptor = pool.get_message_by_name("package.MyMessage").unwrap();

let json = r#"{ "foo": 150 }"#;
let mut deserializer = Deserializer::from_str(json);
let dynamic_message = DynamicMessage::deserialize(message_descriptor, &mut deserializer).unwrap();
deserializer.end().unwrap();

assert_eq!(dynamic_message.get_field_by_name("foo").unwrap().as_ref(), &Value::I32(150));

Re-exports

• pub use prost;
• pub use prost::bytes;
• pub use prost_types;

Structs

• DescriptorError
  An error that may occur while creating a DescriptorPool.
• DescriptorPool
  A DescriptorPool is a collection of related descriptors. Typically it will be created from a FileDescriptorSet output by the protobuf compiler (see DescriptorPool::from_file_descriptor_set) but it may also be built up by adding files individually.
• DeserializeOptions
  Options to control deserialization of messages.
• DynamicMessage
  DynamicMessage provides encoding, decoding and reflection of a protobuf message.
• EnumDescriptor
  A protobuf enum type.
• EnumValueDescriptor
  A value in a protobuf enum type.
• ExtensionDescriptor
  A protobuf extension field definition.
• FieldDescriptor
  A protobuf message definition.
• FileDescriptor
  A single source file containing protobuf messages and services.
• MessageDescriptor
  A protobuf message definition.
• MethodDescriptor
  A method definition for a ServiceDescriptor.
• OneofDescriptor
  A oneof field in a protobuf message.
• SerializeOptions
  Options to control serialization of messages.
• ServiceDescriptor
  A protobuf service definition.

Enums

• Cardinality
  Cardinality determines whether a field is optional, required, or repeated.
• Kind
  The type of a protobuf message field.
• MapKey
  A dynamically-typed key for a protobuf map.
• SetFieldError
  Error type returned by DynamicMessage::try_set_field().
• Syntax
  The syntax of a proto file.
• Value
  A dynamically-typed protobuf value.

Traits

• ReflectMessage
  Trait for message types that support reflection.