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05-protobuf-annotations.md

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Protocol buffer Annotations

This document explains the various protobuf scalars that have been added to make working with protobuf easier for Cosmos SDK application developers.

Signer

Signer specifies which field should be used to determine the signer of a message for the Cosmos SDK. This field can be used for clients as well to infer which field should be used to determine the signer of a message.

Read more about the signer field here.

https://github.com/cosmos/cosmos-sdk/blob/e6848d99b55a65d014375b295bdd7f9641aac95e/proto/cosmos/bank/v1beta1/tx.proto#L40
option (cosmos.msg.v1.signer) = "from_address";

Scalar

The scalar type defines a way for clients to understand how to construct protobuf messages according to what is expected by the module and sdk.

(cosmos_proto.scalar) = "cosmos.AddressString"

Example of account address string scalar:

https://github.com/cosmos/cosmos-sdk/blob/e6848d99b55a65d014375b295bdd7f9641aac95e/proto/cosmos/bank/v1beta1/tx.proto#L46

Example of validator address string scalar:

https://github.com/cosmos/cosmos-sdk/blob/e8f28bf5db18b8d6b7e0d94b542ce4cf48fed9d6/proto/cosmos/distribution/v1beta1/query.proto#L87

Example of pubkey scalar:

https://github.com/cosmos/cosmos-sdk/blob/11068bfbcd44a7db8af63b6a8aa079b1718f6040/proto/cosmos/staking/v1beta1/tx.proto#L94

Example of Decimals scalar:

https://github.com/cosmos/cosmos-sdk/blob/e8f28bf5db18b8d6b7e0d94b542ce4cf48fed9d6/proto/cosmos/distribution/v1beta1/distribution.proto#L26

Example of Int scalar:

https://github.com/cosmos/cosmos-sdk/blob/e8f28bf5db18b8d6b7e0d94b542ce4cf48fed9d6/proto/cosmos/gov/v1/gov.proto#L137

There are a few options for what can be provided as a scalar: cosmos.AddressString, cosmos.ValidatorAddressString, cosmos.ConsensusAddressString, cosmos.Int, cosmos.Dec.

Implements_Interface

Implement interface is used to provide information to client tooling like telescope on how to encode and decode protobuf messages.

option (cosmos_proto.implements_interface) = "cosmos.auth.v1beta1.AccountI";

Method,Field,Message Added In

method_added_in, field_added_in and message_added_in are annotations to denotate to clients that a field has been supported in a later version. This is useful when new methods or fields are added in later versions and that the client needs to be aware of what it can call.

The annotation should be worded as follow:

option (cosmos_proto.method_added_in) = "cosmos-sdk v0.50.1";
option (cosmos_proto.method_added_in) = "x/epochs v1.0.0";
option (cosmos_proto.method_added_in) = "simapp v24.0.0";

Amino

The amino codec was removed in v0.50+, this means there is not a need register legacyAminoCodec. To replace the amino codec, Amino protobuf annotations are used to provide information to the amino codec on how to encode and decode protobuf messages.

:::note Amino annotations are only used for backwards compatibility with amino. :::

The below annotations are used to provide information to the amino codec on how to encode and decode protobuf messages in a backwards compatible manner.

Name

Name specifies the amino name that would show up for the user in order for them see which message they are signing.

option (amino.name) = "cosmos-sdk/BaseAccount";
https://github.com/cosmos/cosmos-sdk/blob/e8f28bf5db18b8d6b7e0d94b542ce4cf48fed9d6/proto/cosmos/bank/v1beta1/tx.proto#L41

Field_Name

Field name specifies the amino name that would show up for the user in order for them see which field they are signing.

uint64 height = 1 [(amino.field_name) = "public_key"];
https://github.com/cosmos/cosmos-sdk/blob/e8f28bf5db18b8d6b7e0d94b542ce4cf48fed9d6/proto/cosmos/distribution/v1beta1/distribution.proto#L166

Dont_OmitEmpty

Dont omitempty specifies that the field should not be omitted when encoding to amino.

repeated cosmos.base.v1beta1.Coin amount = 3 [(amino.dont_omitempty)   = true];
https://github.com/cosmos/cosmos-sdk/blob/e8f28bf5db18b8d6b7e0d94b542ce4cf48fed9d6/proto/cosmos/bank/v1beta1/bank.proto#L56

Encoding

Encoding instructs the amino json marshaler how to encode certain fields that may differ from the standard encoding behaviour. The most common example of this is how repeated cosmos.base.v1beta1.Coin is encoded when using the amino json encoding format. The legacy_coins option tells the json marshaler how to encode a null slice of cosmos.base.v1beta1.Coin.

(amino.encoding)         = "legacy_coins",
https://github.com/cosmos/cosmos-sdk/blob/e8f28bf5db18b8d6b7e0d94b542ce4cf48fed9d6/proto/cosmos/bank/v1beta1/genesis.proto#L23

Another example is a protobuf bytes that contains a valid JSON document. The inline_json option tells the json marshaler to embed the JSON bytes into the wrapping document without escaping.

(amino.encoding)         = "inline_json",

E.g. the bytes containing {"foo":123} in the envelope field would lead to the following JSON:

{
  "envelope": {
    "foo": 123
  }
}

If the bytes are not valid JSON, this leads to JSON broken documents. Thus a JSON validity check needs to be in place at some point of the process.