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• Iroha 2 peer receive messages from it clients primarily serialized in SCALE  codec, but also some endpoint receive accept JSON messages
• Iroha 2 has some client libraries in development (Rust, Java/Kotlin, JavaScript, Python)
• Scale codec do not need the name of the properties and containers, but JSON do need

Problem

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• Code generation of models and serialization/deserialization tests
• Type safe checks in clients code (if programming language support type safety)

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Basically we can consider 3 types of items

1. Scalars 

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In SCALE integers can be encoded as fixed-width integer and compact integer. Compact integer itself has

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4 modes. So generally we have

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5 ways to serde integer (1 fixed-width +

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4 modes of compact integers) 

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{
  "u8": {
    "Int": "FixedWidth"
  },
  "iroha_introspect::Compact<u8>": {
    "Int": "Compact"
  }
}

2. Built-in basic types

•  bool: no tricks here
• String

{
  "alloc::string::String": "String",
  "bool": "Bool"
}

3

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2. Built-in containers 

• Option / Result / Map / Vec

  / typle / array

  : basically we are interested in only inner values of the container

  Code Block
  language js
  { "core::option::Option<iroha_data_model::isi::Instruction>": { "Option": "iroha_data_model::isi::Instruction" }, "core::result::Result<i32, i32>": { "Result": { "ok": "i32", "err": "i32" } }, "alloc::collections::BTreeMap<alloc::string::String, i32>": { "Map": { "key": "alloc::string::String", "value": "i32" } }, "alloc::vec::Vec<i32>": { "Vec": "i32" } }

  
  

43. Custom containers 

• Structures

• Enums: similar to Structures but also every variant of enum has a discriminator that used in Scale. By default based on 0, but can be overriden by attributes

Alternatives

Present at least two alternatives to the solution you suggested

Concerns

Write down all the things that worry you or other stakeholders

Assumptions

Document any assumption that you made

Risks

• Named structures – structures which have field names
• Unnamed structures – structures with no field names (like zero sized structures in rust, or tuples, or struct WrappedTuple(i32, i32))
• Enums
  

  
  

  Code Block
  language js
  { "iroha_crypto::PublicKey": { "NamedStruct": { "declarations": [ { "name": "digest_function", "ty": "alloc::string::String" }, { "name": "payload", "ty": "alloc::vec::Vec<u8>" } ] } }, "iroha_data_model::account::SignatureCheckCondition": { "UnnamedStruct": { "types": [ "iroha_data_model::expression::EvaluatesTo<bool>" ] } }, "iroha_data_model::events::pipeline::EntityType": { "Enum": { "variants": [ { "name": "Block", "discriminant": 0, "ty": null }, { "name": "Transaction", "discriminant": 1, "ty": null } ] } }, }

  
  

Concerns

Currently we are not support polymorphism via TraitObjects, but it can be implemented if necessaryList all risks in form "description \[probability (from 0 to 9); impact (from 0 to 9)\]"

Additional Information

1. Scale codec description in Substrate docs [https://substrate.dev/docs/en/knowledgebase/advanced/codec]
2. Scale codec Github page [https://github.com/paritytech/parity-scale-codec]